A method for melting and casting a copper-steel bimetallic cylinder

Abstract

The present invention provides a method for casting a copper-steel bimetallic cylinder body, which belongs to the technical field of pump body part processing. The casting method comprises: pre-treating a steel base and a copper alloy, heating and keeping them warm together; then cooling, wherein the cooling is divided into four stages, wherein the purge direction of the first, third, and fourth stages of cooling is from bottom to top, the purge direction of the second stage of cooling is from top to bottom, and the copper liquid is completely solidified after the third stage of cooling; and after the cooling is completed, tempering treatment is performed to obtain a copper-steel bimetallic cylinder body. During the cylinder body casting process, the present invention cools the heated cylinder body in multiple stages, controls the gas purge direction at different cooling stages, achieves rapid solidification of the copper liquid, avoids the formation of undulations in the copper liquid, effectively controls solidification defects, and obtains a dense copper layer. Through the final stage of cooling and tempering process control, the matrix structure of the steel base is regulated to form tempered bainite, thereby improving the mechanical properties of the cylinder body.

Description

Technical Field

[0001] The invention belongs to the technical field of pump body parts processing and relates to a melting and casting method of a copper-steel bimetallic cylinder body. Background Art

[0002] Steel, one of the most widely used metal materials, can be combined with various materials to form diverse composite materials. For example, steel combined with copper and copper alloys can create copper-steel composites. These materials, while maintaining the properties of steel, combine copper's inherent ductility, friction reduction, electrical conductivity, and thermal conductivity, offering promising applications thanks to their complementary advantages. Copper-steel bimetallic composites, with their unique material properties, are widely used in wear- and impact-resistant applications. A typical application is in hydraulic cylinders, a key component of plunger pumps. Their performance and quality directly impact their transmission efficiency and service life.

[0003] At present, one of the common methods for producing copper-steel bimetallic cylinder bodies is the casting method, which utilizes the difference in melting points between copper and steel, uses steel as a matrix, and clads copper on the surface of the steel matrix. During operation, it is necessary to first process the molten pool tank, then place the copper alloy into the molten pool tank, and place the entire workpiece into a sintering furnace to heat it up. After the copper alloy melts, it spreads on the surface of the steel matrix, and forms a bimetallic cylinder body after cooling. It has the advantages of high production efficiency and low production cost. According to the processing process of the copper-steel bimetallic cylinder body, the volume of the steel matrix is ​​much larger than the volume of the copper layer. During the solidification process, the copper liquid at the copper-steel interface is affected by the heat of the steel matrix, resulting in slow solidification of the copper liquid and poor density. It is easy to produce defects such as pores and looseness at the interface. In addition, the matrix structure of the cylinder body after the traditional casting process is pearlite-ferrite, and its performance cannot meet the future demand for high-pressure hydraulic systems.

[0004] CN 110434315A discloses a heating and cooling method for the molten copper bimetallic cylinder. The method includes the steps of surface treatment of the steel substrate, preheating, staged heating, variable speed cooling, and auxiliary crystallization. After the steel substrate is molten, the copper alloy is placed in a copper water pool, a capping device is installed, and then the copper alloy is transferred to the preheating zone of the casting furnace. After preheating, the copper alloy is transferred to the heating zone for staged heating and heat preservation, and finally variable speed cooling is performed. The variable speed cooling is achieved by using different cooling media or combinations, and can be divided into rapid cooling, medium cooling, and slow cooling. The patent focuses on the addition of a cap to form a temperature gradient in the copper liquid, so that the copper liquid solidifies preferentially at the interface, eliminating solidification defects. However, during cooling, the cooling medium needs to act on the steel substrate, and the heat needs to be transferred to the copper layer. The cooling rate is slow, which cannot achieve the purpose of rapid solidification. It also easily causes the density of the copper layer to decrease, and the consistency of the casting quality is poor.

[0005] CN 119140794A discloses a method for preparing a casting cylinder and a casting cylinder. The method comprises: sealing the bottom of a plunger hole on the cylinder, sintering a copper alloy and the casting cylinder; cooling the casting cylinder; and finishing the cooled casting cylinder. The cooling method employs air cooling and liquid cooling in a staged manner, specifically comprising: first cooling the cylinder in air, then placing the cylinder in a coolant, where the coolant does not completely immerse the casting cylinder, then lifting the cylinder from the coolant to above the coolant, cooling it in air, and finally immersing the cylinder in the coolant again, cooling until the cylinder partially turns black, and then completing the cooling process. Although the cooling process in this method is divided into multiple stages of cooling, it still acts on the underlying substrate, cooling the molten copper through heat conduction, and cannot prevent the molten copper from solidifying at the interface first, thus failing to effectively control solidification defects.

[0006] In summary, for the melting and casting process of copper-steel bimetallic cylinder, it is particularly necessary to improve the solidification process of copper liquid so that it can achieve rapid solidification of copper liquid, effectively control solidification defects, improve the density of copper layer, and at the same time improve the organizational structure of copper matrix and improve the mechanical properties of casting cylinder. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a copper-steel bimetallic cylinder casting method. During the cylinder casting process, the heated cylinder is subjected to multi-stage cooling to achieve rapid cooling and solidification of the copper liquid, effectively control solidification defects, obtain a dense copper layer, regulate the matrix structure of the steel matrix, improve its mechanical properties, and achieve a high yield rate in the cylinder casting process.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0010] (1) After pretreatment, the steel matrix and copper alloy are placed together in a melting and casting device and then heated and kept warm;

[0011] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is divided into four stages. The purge direction of the first, third and fourth stages of cooling is from bottom to top, and the purge direction of the second stage of cooling is from top to bottom. After the third stage of cooling, the molten copper alloy has been solidified.

[0012] (3) After cooling in step (2), the cylinder body is tempered to obtain a copper-steel dual alloy cylinder body.

[0013] In the present invention, for the melting and casting processing of a copper-steel bimetallic cylinder body, a steel base and a copper alloy are used as raw materials, the copper alloy is melted through a heating process, and the copper layer and the steel base are composited to obtain the cylinder body by controlling the cooling process; the cooling is divided into a multi-stage cooling process according to the positional relationship and volume ratio of the steel base and the copper layer, and the gas purge direction in different cooling stages is controlled, so that the rapid solidification of the copper liquid can be achieved, the formation of undulations in the copper liquid can be avoided, solidification defects can be effectively controlled, and a dense copper layer can be obtained; and then, through the control of the last stage of cooling and the tempering process, the matrix structure of the steel base is regulated to form tempered bainite, thereby improving the mechanical properties of the cylinder body and achieving a high yield rate of the cylinder body; the method has a reasonable operation design and high production efficiency, can effectively shorten the processing time, and reduce the production cost.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, the material of the steel substrate in step (1) is alloy steel, including chromium-molybdenum steel or chromium steel.

[0016] Preferably, the chromium-molybdenum steel comprises 42CrMoS4 or 30CrMo, and the chromium steel comprises 40Cr;

[0017] Preferably, the metallographic structure of the 42CrMoS4 is pearlite+ferrite.

[0018] In the present invention, when the chromium-molybdenum steel is 42CrMoS4, its element composition, by mass fraction, includes C 0.40-0.45%, such as 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45% or 0.46%, Si ≤ 0.40%, such as 0.40%, 0.38%, 0.35%, 0.32%, 0.30%, 0.25% or 0.20%, Mn 0.60-0.90%, such as 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85% or 0.90%, P ≤ 0.025%, such as 0.025%, 0.022%, 0.020%, 0.018%, 0.015% or 0.010%, S 0.010~0.018%, such as 0.010%, 0.012%, 0.014%, 0.015%, 0.016% or 0.018%, Cr 0.90~1.20%, such as 0.90%, 0.95%, 1.00%, 1.05%, 1.10%, 1.15% or 1.20%, Mo0.19~0.30%, such as 0.19%, 0.20%, 0.22%, 0.25%, 0.27% or 0.30%, Cu≤0.20%, such as 0.20%, 0.18%, 0.15%, 0.12%, 0.10% or 0.05%, Ni≤0.30%, such as 0.30%, 0.27%, 0.25%, 0.22%, 0.20%, 0.18%, 0.15% or 0.10%, etc.; but are not limited to the listed values, and other values ​​not listed within the respective numerical ranges are equally applicable.

[0019] Preferably, in step (1), a molten pool groove and a boss are provided at the upper end of the steel substrate, the boss is located in the middle position, and the molten pool groove is arranged around the boss.

[0020] Preferably, a center hole is provided at the center position of the steel base, and the center hole is divided into upper and lower sections with different diameters, the diameter of the upper center hole is smaller than the diameter of the lower center hole, and the upper center hole passes through the boss longitudinally.

[0021] In the present invention, the boss in the steel matrix plays a role of a heat node during the solidification stage of the copper liquid, so that the solidification direction of the copper liquid is from outside to inside, the last solidification area is gathered around the boss, and solidification defects such as loose shrinkage cavities are effectively controlled.

[0022] As a preferred technical solution of the present invention, the copper alloy in step (1) includes any one of tin-lead bronze, tin bronze, bismuth bronze, aluminum bronze or silicon bronze, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of tin-lead bronze and bismuth bronze, a combination of tin bronze and aluminum bronze, a combination of aluminum bronze and silicon bronze, a combination of tin-lead bronze, tin bronze and bismuth bronze, etc.

[0023] Preferably, the tin-lead bronze is CuSn10Pb10 or CuSn7Pb15, and its metallographic structure is α-Cu+spherical rod-shaped Pb.

[0024] In the present invention, the elemental chemical composition of the CuSn10Pb10 is calculated by mass, including Sn 9.35-10.95%, such as 9.35%, 9.50%, 9.75%, 10.00%, 10.20%, 10.50%, 10.75% or 10.95%, etc., Pb 9.21-11.58%, such as 9.21%, 9.50%, 9.75%, 10.00%, 10.50%, 11.00% or 11.58%, etc., Ni 1.24-1.86%, such as 1.24%, 1.30%, 1.40%, 1.50%, 1.60%, 1.70%, 1.80% or 1.86%, etc., Zn 0.01-0.05%, such as 0.01%, 0.02%, 0.03%, 0.04% or 0.05%, etc., P 0.1% or less, such as 0.1%, 0.09%, 0.08%, 0.07%, 0.06% or 0.05%, etc.; but are not limited to the listed values, and other unlisted values ​​within the respective numerical ranges are also applicable.

[0025] Preferably, the copper alloy is placed in a molten pool tank of the steel substrate.

[0026] As a preferred technical solution of the present invention, the pretreatment of the steel substrate and the copper alloy in step (1) is cleaning with an alkaline cleaning agent.

[0027] Preferably, the alkaline cleaning agent comprises amines, organic acids, surfactants and water.

[0028] In the present invention, in the composition of the alkaline cleaning agent, the amines include ethanolamine, diethanolamine, triethanolamine, cycloethylamine, etc., the organic acid can be selected from citric acid, oxalic acid, ethylenediaminetetraacetic acid, etc., and the surfactant can be selected from sodium dodecylbenzenesulfonate, sodium lauryl polyether sulfate, cocamidopropyl betaine, etc.; the amines are alkaline, and the organic acid acts as a buffer to achieve a stable pH value of the cleaning agent.

[0029] Preferably, the concentration of the alkaline cleaning agent is 1~3wt%, for example, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.2wt%, 2.5wt%, 2.7wt% or 3wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0030] Preferably, the cleaning temperature is 50~70℃, for example, 50℃, 52℃, 55℃, 58℃, 60℃, 62℃, 65℃, 68℃ or 70℃, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; the time is 20~30min, for example, 20min, 22min, 24min, 25min, 27min, 28min or 30min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the melting and casting equipment in step (1) includes a melting and casting furnace. After the copper alloy is placed in the molten pool tank of the steel substrate, the two are placed together in the melting and casting furnace.

[0032] Preferably, the heating in step (1) is divided into two stages of heating, the temperature of the first stage heating is 790~980℃, for example, 790℃, 800℃, 820℃, 850℃, 880℃, 900℃, 920℃, 940℃, 960℃ or 980℃, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the temperature of the second stage heating is 1020~1040℃, for example, 1020℃, 1022℃, 1025℃, 1028℃, 1030℃, 1032℃, 1035℃, 1038℃ or 1040℃, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0033] Preferably, the holding time of the first stage heating is 60~100min, for example, 60min, 65min, 70min, 75min, 80min, 85min, 90min, 95min or 100min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable; the holding time of the second stage heating is 50~80min, for example, 50min, 55min, 60min, 65min, 70min, 75min or 80min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] As a preferred technical solution of the present invention, the cooling in step (2) is carried out in a cooling furnace, and the heated steel substrate and molten copper liquid are transferred from the melting and casting furnace to the cooling furnace.

[0035] In the present invention, the melting furnace and the cooling furnace belong to different areas of the same equipment and can be automatically transferred after heating is completed without manual operation.

[0036] Preferably, the cooling medium used in step (2) is liquid nitrogen, and blowing is performed during the process of liquid nitrogen being gasified into nitrogen gas, and the blowing direction of the gas is controlled.

[0037] Preferably, the blowing direction is achieved by fans arranged at the top and bottom ends of the cooling furnace, and the gas flow rate is controlled by the rotation speed of the fans.

[0038] In the present invention, the cooling process after the cylinder body is heated can be mainly divided into the solidification of the copper liquid and the cooling process of the cylinder body after solidification, which is achieved by changing the liquid nitrogen flow rate, the blowing direction and the gas flow rate. The liquid nitrogen flow rate is achieved by adjusting the pressure in the furnace, the blowing direction is achieved by opening and closing the fans built into the top and bottom ends of the furnace, and the gas flow rate is achieved by adjusting the fan speed.

[0039] As a preferred technical solution of the present invention, in step (2), the blowing direction during the first stage cooling is vertically upward from the bottom of the steel substrate, the nitrogen pressure is 1000~4000mbar, for example, 1000mbar, 1500mbar, 2000mbar, 2500mbar, 3000mbar, 3500mbar or 4000mbar, etc., the fan speed is 800~1200rpm, for example, 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm, 1050rpm, 1100rpm, 1150rpm or 1200rpm, etc., and the cooling time is 2~6s, for example, 2s, 3s, 4s, 5s or 6s, etc.; but it is not limited to the listed values, and other values ​​not listed within the respective numerical ranges are also applicable.

[0040] Preferably, in step (2), the blowing direction during the second stage cooling is vertical to the upper end surface of the steel substrate and downward, the nitrogen pressure is 1000~4000mbar, for example, 1000mbar, 1500mbar, 2000mbar, 2500mbar, 3000mbar, 3500mbar or 4000mbar, etc., the fan speed is 1500~2500rpm, for example, 1500rpm, 1600rpm, 1800rpm, 2000rpm, 2200rpm, 2400rpm or 2500rpm, etc., and the cooling time is 2~6s, for example, 2s, 3s, 4s, 5s or 6s, etc.; but it is not limited to the listed values, and other values ​​not listed within the respective numerical ranges are also applicable.

[0041] Preferably, the blowing direction during the third stage cooling in step (3) is vertical to the bottom surface of the steel substrate and upward, the nitrogen pressure is 1000~4000mbar, for example, 1000mbar, 1500mbar, 2000mbar, 2500mbar, 3000mbar, 3500mbar or 4000mbar, etc., the fan speed is 2500~3500rpm, for example, 2500rpm, 2600rpm, 2800rpm, 3000rpm, 3200rpm, 3400rpm or 3500rpm, etc., and the cooling time is 2~6s, for example, 2s, 3s, 4s, 5s or 6s, etc.; but it is not limited to the listed values, and other values ​​not listed within the respective numerical ranges are also applicable.

[0042] Preferably, after three stages of cooling, the copper liquid is completely solidified, and the cylinder temperature at this time is 880-950°C, for example, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C or 950°C, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0043] In the present invention, liquid nitrogen with a small flow rate is used for cooling in the first three stages, and the gas flow rate is increased step by step. The first stage of cooling forms a shell paste on the surface of the copper liquid. The second stage directly cools the copper liquid, which can avoid dynamic fluctuations caused by direct blowing of the copper liquid. In this process, most of the copper liquid is completely solidified. The third stage of cooling cools the steel substrate at the lower end again, so that the copper liquid near the middle boss at the upper end of the steel substrate is completely solidified. That is, the cooling in the first three stages can achieve complete solidification of the copper liquid and make the overall temperature of the cylinder body above the austenite temperature of the alloy steel.

[0044] As a preferred technical solution of the present invention, the blowing direction during the fourth stage of cooling is vertically upward from the bottom of the steel substrate, and the liquid nitrogen flow rate is increased for rapid cooling. The cooling rate at this time is 1.2~5℃ / s, for example, 1.2℃ / s, 1.5℃ / s, 2℃ / s, 2.5℃ / s, 3℃ / s, 3.5℃ / s, 4℃ / s, 4.5℃ / s or 5℃ / s, etc., but is not limited to the listed values, but other unlisted values ​​within this numerical range are also applicable.

[0045] Preferably, the nitrogen pressure of the fourth stage cooling is 8000~14000mbar, for example, 8000mbar, 9000mbar, 10000mbar, 11000mbar, 12000mbar, 13000mbar or 14000mbar, etc., the fan speed is 2500~3500rpm, for example, 2500rpm, 2600rpm, 2800rpm, 3000rpm, 3200rpm, 3400rpm or 3500rpm, etc., and the cooling endpoint temperature is below 80℃, for example, 80℃, 75℃, 70℃, 65℃ or 60℃, etc.; however, it is not limited to the listed values, and other values ​​not listed within the respective numerical ranges are also applicable.

[0046] Preferably, after the fourth stage of cooling is completed, the cylinder is taken out and continues to be air-cooled to room temperature.

[0047] In the present invention, the cooling in the fourth stage is rapid cooling, using a large flow of liquid nitrogen and a relatively large gas flow rate, so that the metallographic structure of the steel matrix is ​​transformed into martensite.

[0048] As a preferred technical solution of the present invention, the temperature of the tempering treatment in step (3) is 560~630℃, for example, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃ or 630℃, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the holding time of the tempering treatment in step (3) is 120-180 min, for example, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min or 180 min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the cooling method after the tempering treatment in step (3) is to directly take out of the furnace and air-cool to room temperature or to cool in the furnace to below 150°C and then take out of the furnace and air-cool to room temperature, such as 150°C, 145°C, 140°C, 135°C, 130°C, 125°C or 120°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the metallographic structure of the steel matrix after the tempering treatment in step (3) is tempered bainite.

[0052] In the present invention, after the fourth stage of strong cooling, the steel matrix part is further subjected to high-temperature tempering treatment, so that the metallographic structure of the steel matrix can be transformed from martensite to tempered bainite, and it has excellent strength and toughness and excellent mechanical properties. This is required based on the application of the cylinder body. The bimetallic cylinder body is a key component in a plunger pump or motor. Its function is to cooperate with the plunger and the distribution plate to form a closed volume, realize oil suction and discharge to provide power. When in service, it is subjected to the impact of hydraulic oil and friction of the wear pair, so it needs to have good strength and excellent fatigue resistance, which is related to the strength and toughness of the steel matrix and the density of the copper layer.

[0053] As a preferred technical solution of the present invention, the melting and casting method comprises the following steps:

[0054] (1) Pre-treating a steel substrate and a copper alloy, wherein the material of the steel substrate comprises chromium-molybdenum steel or chromium steel, a molten pool groove and a boss are provided at the upper end of the steel substrate, the boss is located in the middle, and the molten pool groove is arranged around the boss, and the copper alloy comprises any one or a combination of at least two of tin-lead bronze, tin bronze, bismuth bronze, aluminum bronze or silicon bronze, and the pre-treatment is performed by cleaning with an alkaline cleaning agent, wherein the composition of the alkaline cleaning agent comprises amines, organic acids, surfactants and water, and the concentration of the alkaline cleaning agent is 1 to 3wt%, the cleaning temperature is 50-70°C, the time is 20-30min, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in the molten pool tank of the steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The temperature of the first stage is 790-980°C, the insulation time is 60-100min, and the temperature of the second stage is 1020-1040°C, and the insulation time is 50-80min.

[0055] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 1000~4000mbar, and the fan speed is 800~1200r pm, the cooling time is 2~6s, the nitrogen pressure during the second stage cooling is 1000~4000mbar, the fan speed is 1500~2500rpm, and the cooling time is 2~6s. The nitrogen pressure during the third stage cooling is 1000~4000mbar, the fan speed is 2500~3500rpm, and the cooling time is 2~6s. After the third stage cooling, the molten copper alloy has been solidified, and the cylinder temperature at this time is 880~950℃; the cooling rate of the fourth stage cooling is 1.2~5℃ / s, the nitrogen pressure is 8000~14000mbar, the fan speed is 2500~3500rpm, and the cooling end temperature is below 80℃, then the cylinder is removed and continued to air cool to room temperature;

[0056] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 560-630°C, and the holding time is 120-180 min. The cooling method after the tempering treatment is to directly take the cylinder out of the furnace and air-cool to room temperature or to cool the cylinder in the furnace to below 150°C and then take the cylinder out of the furnace and air-cool to room temperature to obtain a copper-steel dual alloy cylinder body. The metallographic structure of the steel matrix after the tempering treatment is tempered bainite.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The method of the present invention performs multi-stage cooling on the heated cylinder during the cylinder casting process, and controls the gas purge direction at different cooling stages, thereby achieving rapid solidification of the copper liquid and preventing the formation of undulations in the copper liquid, effectively controlling solidification defects, and obtaining a dense copper layer;

[0059] (2) The present invention regulates the matrix structure of the steel matrix by controlling the final cooling and tempering process to form tempered bainite, thereby improving the mechanical properties of the cylinder body and increasing the yield of the cylinder body to more than 98%;

[0060] (3) The method of the present invention has a reasonable operation design and high production efficiency, which can effectively shorten the processing time and reduce the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a schematic structural diagram of a steel substrate provided in Example 1 of the present invention;

[0062] Figure 2 The metallographic structure of the entire copper layer in the copper-steel bimetallic cylinder provided in Example 1 of the present invention;

[0063] Figure 3 The metallographic structure of a local portion of the copper layer in the copper-steel bimetallic cylinder provided in Example 1 of the present invention;

[0064] Figure 4 The metallographic structure of the steel matrix in the copper-steel bimetallic cylinder provided in Example 1 of the present invention;

[0065] Figure 5 The metallographic structure of the entire copper layer in the copper-steel bimetallic cylinder provided in Example 2 of the present invention;

[0066] Figure 6 This is the metallographic structure of a local portion of the copper layer in the copper-steel bimetallic cylinder provided in Example 2 of the present invention;

[0067] Figure 7 The metallographic structure of the steel matrix in the copper-steel bimetallic cylinder provided in Example 2 of the present invention;

[0068] Among them, 1-molten pool groove, 2-boss, 3-upper end center hole, 4-lower end center hole. DETAILED DESCRIPTION

[0069] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0070] The following are typical but non-limiting examples of the present invention:

[0071] Example 1:

[0072] This embodiment provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0073] (1) Pre-treating the steel substrate and the copper alloy. The material of the steel substrate is chromium-molybdenum steel 42CrMoS4. The structural diagram of the steel substrate is as shown in FIG. Figure 1As shown, a molten pool groove 1 and a boss 2 are provided at its upper end, the boss 2 is located in the middle position, the molten pool groove 1 is arranged around the boss 2, a center hole is provided at the center position of the steel substrate, and the center hole is divided into an upper and lower section with different diameters, the diameter of the upper center hole 3 is smaller than the diameter of the lower center hole 4, and the upper center hole 3 longitudinally penetrates the boss 2; the copper alloy is tin-lead bronze CuSn10Pb10, and the pretreatment is cleaning with an alkaline cleaning agent, and the composition of the alkaline cleaning agent includes ethanolamine and Citric acid and sodium dodecylbenzenesulfonate, the total concentration of the alkaline cleaning agent is 2wt%, the cleaning temperature is 60°C, the time is 25 minutes, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in the molten pool tank of the steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The temperature of the first stage is 840°C and the insulation time is 70 minutes. The temperature of the second stage is 1025°C and the insulation time is 75 minutes.

[0074] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the casting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 4 000mbar, the fan speed is 1000rpm, and the cooling time is 4s. The nitrogen pressure during the second stage of cooling is 4000mbar, the fan speed is 2000rpm, and the cooling time is 4s. The nitrogen pressure during the third stage of cooling is 4000mbar, the fan speed is 3000rpm, and the cooling time is 4s. After the third stage of cooling, the molten copper alloy has solidified and the cylinder temperature is 900℃. The cooling rate of the fourth stage of cooling is 2.5℃ / s, the nitrogen pressure is 12000mbar, the fan speed is 3000rpm, and the cooling end temperature is 80℃. Then the cylinder is taken out and air-cooled to room temperature.

[0075] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 600°C and the holding time is 120 minutes. The cooling method after the tempering treatment is to directly take the cylinder out of the furnace and air-cool it to room temperature to obtain a copper-steel dual alloy cylinder body.

[0076] In this embodiment, the prepared copper-steel bimetallic cylinder was observed using an optical microscope. The metallographic structure of the copper layer in the cylinder was as follows: Figure 2 and 3 As shown in Figure 2, the metallographic structure of the steel matrix is ​​as follows: Figure 4 As shown; the mechanical properties of the copper-steel bimetallic cylinder were tested, where the hardness test was carried out using a Brinell hardness tester. The copper layer was tested on the surface, and the steel matrix was tested on the bottom of the cylinder (the surface decarburized layer was removed before testing). The sampling position for the steel matrix tensile strength and impact energy tests was the center of the cylinder, that is, 1 / 2 of the cylinder radius.

[0077] In this embodiment, Figure 2 The metallographic structure of the entire copper layer is Figure 3 The metallographic structure of a local position in the copper layer, the Pb phase in the copper layer is small and uniform, the shrinkage is all concentrated in the central boss, and the rest of the position is dense and has no shrinkage; Figure 4 It can be seen that the metallographic structure of the steel matrix after tempering treatment is tempered troostite;

[0078] According to the above mechanical properties test, the hardness of the steel matrix in the cylinder body is 260~280 HBW2.5 / 187.5, the tensile strength of the core is 890MPa, the impact energy is 89.5J, and the hardness of the copper layer is 118 HBW2.5 / 62.5.

[0079] Example 2:

[0080] This embodiment provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0081] (1) Pre-treating a steel substrate and a copper alloy. The steel substrate is made of chromium-molybdenum steel 42CrMoS4. A molten pool groove 1 and a boss 2 are provided at the upper end of the steel substrate. The boss 2 is located in the middle. The molten pool groove 1 is arranged around the boss 2. A center hole is provided at the center of the steel substrate. The center hole is divided into two sections with different diameters. The diameter of the upper center hole 3 is smaller than the diameter of the lower center hole 4. The upper center hole 3 longitudinally penetrates the boss 2. The copper alloy is tin-lead bronze CuSn10Pb10. The pre-treatment is cleaning with an alkaline cleaning agent. The composition includes ethanolamine, citric acid and sodium dodecylbenzenesulfonate in a mass ratio of 4:1:0.8, the total concentration of the alkaline cleaning agent is 1wt%, the cleaning temperature is 70°C, the cleaning time is 20 minutes, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in a molten pool tank of a steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The temperature of the first stage is 950°C and the insulation time is 100 minutes. The temperature of the second stage is 1040°C and the insulation time is 80 minutes.

[0082] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the casting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 1000mbar, fan speed is 800rpm, cooling time is 6s, the nitrogen pressure during the second stage cooling is 1500mbar, fan speed is 1600rpm, cooling time is 6s, the nitrogen pressure during the third stage cooling is 1000mbar, fan speed is 2500rpm, cooling time is 6s, after the third stage cooling, the molten copper alloy has been solidified, and the cylinder temperature at this time is 950℃; the cooling rate of the fourth stage cooling is 5℃ / s, the nitrogen pressure is 14000mbar, the fan speed is 3500rpm, the cooling end temperature is 75℃, then the cylinder is removed and air-cooled to room temperature;

[0083] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 560°C and the holding time is 180 minutes. The cooling method after the tempering treatment is to directly take the cylinder out of the furnace and air-cool it to room temperature to obtain a copper-steel dual alloy cylinder body.

[0084] In this embodiment, the prepared copper-steel bimetallic cylinder was observed using an optical microscope. The metallographic structure of the copper layer in the cylinder was as follows: Figure 5 and 6 As shown in Figure 2, the metallographic structure of the steel matrix is ​​as follows: Figure 7 As shown; and the copper-steel bimetallic cylinder was subjected to mechanical property testing, and the testing conditions were the same as those in Example 1.

[0085] In this embodiment, Figure 5 The metallographic structure of the entire copper layer is Figure 6 The metallographic structure of a local position in the copper layer, the Pb phase in the copper layer is small and uniform, the shrinkage is all concentrated in the central boss, and the rest of the position is dense and has no shrinkage; Figure 7 It can be seen that the metallographic structure of the steel matrix after tempering treatment is tempered troostite;

[0086] According to the above mechanical properties test, the hardness of the steel matrix in the cylinder body is 260~300 HBW2.5 / 187.5, the tensile strength of the core is 867MPa, the impact energy is 99J, and the hardness of the copper layer is 90 HBW2.5 / 62.5.

[0087] Example 3:

[0088] This embodiment provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0089] (1) Pre-treating the steel substrate and the copper alloy. The steel substrate is made of chromium-molybdenum steel 42CrMoS4. A molten pool groove 1 and a boss 2 are provided at the upper end of the steel substrate. The boss 2 is located in the middle. The molten pool groove 1 is arranged around the boss 2. A center hole is provided at the center of the steel substrate. The center hole is divided into two sections with different diameters. The diameter of the upper center hole 3 is smaller than the diameter of the lower center hole 4. The upper center hole 3 longitudinally penetrates the boss 2. The copper alloy is tin-lead bronze CuSn10Pb10. The pre-treatment is cleaning with an alkaline cleaning agent. The alkaline cleaning agent The composition includes diethanolamine, oxalic acid and sodium dodecylbenzenesulfonate in a mass ratio of 3:1:1, the total concentration of the alkaline cleaning agent is 3wt%, the cleaning temperature is 50°C, the cleaning time is 30 minutes, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in a molten pool tank of a steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The first stage is heated at a temperature of 900°C and a insulation time of 80 minutes. The second stage is heated at a temperature of 1020°C and a insulation time of 60 minutes.

[0090] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans provided at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 2 500mbar, fan speed is 1200rpm, cooling time is 2s, nitrogen pressure during the second stage cooling is 3000mbar, fan speed is 2500rpm, cooling time is 2s, nitrogen pressure during the third stage cooling is 2500mbar, fan speed is 3500rpm, cooling time is 2s, after the third stage cooling, the molten copper alloy has been solidified, and the cylinder temperature at this time is 920℃; the cooling rate of the fourth stage cooling is 1.5℃ / s, nitrogen pressure is 10000mbar, fan speed is 3500rpm, cooling end temperature is 70℃, then remove the cylinder and continue air cooling to room temperature;

[0091] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 630°C and the holding time is 135 minutes. The cooling method after the tempering treatment is to cool to 150°C in the furnace and then air-cool to room temperature to obtain a copper-steel dual alloy cylinder body.

[0092] In this embodiment, the prepared copper-steel bimetallic cylinder body was observed for metallographic structure using an optical microscope. The shrinkage in the copper layer was all concentrated at the central boss, while the remaining parts were dense and shrinkage-free. The mechanical properties of the cylinder body were tested under the same testing conditions as in Example 1. The hardness of the steel matrix in the cylinder body was 273~310 HBW2.5 / 187.5, the tensile strength of the core was 880MPa, the impact energy was 95J, and the hardness of the copper layer was 95 HBW2.5 / 62.5.

[0093] Example 4:

[0094] This embodiment provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0095] (1) Pre-treating a steel substrate and a copper alloy. The steel substrate is made of chromium steel 40Cr. A molten pool groove 1 and a boss 2 are provided at the upper end of the steel substrate. The boss 2 is located in the middle. The molten pool groove 1 is arranged around the boss 2. A center hole is provided at the center of the steel substrate. The center hole is divided into two sections with different diameters. The diameter of the upper center hole 3 is smaller than that of the lower center hole 4. The upper center hole 3 longitudinally penetrates the boss 2. The copper alloy is tin-lead bronze CuSn10Pb10. The pre-treatment is cleaning with an alkaline cleaning agent. The composition of the alkaline cleaning agent includes the following: Diethanolamine, ethylenediaminetetraacetic acid, and sodium lauryl polyether sulfate in a molar ratio of 5:1:1, the total concentration of the alkaline cleaning agent is 2.5wt%, the cleaning temperature is 65°C, the cleaning time is 27 minutes, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in a molten pool tank of a steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The first stage is heated at a temperature of 800°C and a holding time of 90 minutes. The second stage is heated at a temperature of 1030°C and a holding time of 65 minutes.

[0096] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 3 000mbar, the fan speed is 1100rpm, and the cooling time is 3s. The nitrogen pressure during the second stage of cooling is 3000mbar, the fan speed is 2200rpm, and the cooling time is 5s. The nitrogen pressure during the third stage of cooling is 3000mbar, the fan speed is 3200rpm, and the cooling time is 3s. After the third stage of cooling, the molten copper alloy has solidified and the cylinder temperature is 890°C. The cooling rate of the fourth stage of cooling is 3.5°C / s, the nitrogen pressure is 13000mbar, the fan speed is 3200rpm, and the cooling end temperature is 72°C. Then the cylinder is removed and air-cooled to room temperature.

[0097] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 580°C and the holding time is 160 minutes. The cooling method after the tempering treatment is to directly take the cylinder out of the furnace and air-cool it to room temperature to obtain a copper-steel dual alloy cylinder body.

[0098] In this embodiment, the metallographic structure of the prepared copper-steel bimetallic cylinder was observed using an optical microscope. The shrinkage in the copper layer was all concentrated at the central boss, while the remaining parts were dense and shrinkage-free. The mechanical properties of the cylinder were tested under the same testing conditions as in Example 1. The hardness of the steel matrix in the cylinder was 257~298 HBW2.5 / 187.5, the tensile strength of the core was 860MPa, the impact energy was 88J, and the hardness of the copper layer was 93 HBW2.5 / 62.5.

[0099] Example 5:

[0100] This embodiment provides a method for melting and casting a copper-steel bimetallic cylinder, the method comprising the following steps:

[0101] (1) Pre-treating a steel substrate and a copper alloy. The steel substrate is made of chromium-molybdenum steel 30CrMo. A molten pool groove 1 and a boss 2 are provided at the upper end of the steel substrate. The boss 2 is located in the middle. The molten pool groove 1 is arranged around the boss 2. A center hole is provided at the center of the steel substrate. The center hole is divided into two sections with different diameters. The diameter of the upper center hole 3 is smaller than the diameter of the lower center hole 4. The upper center hole 3 longitudinally penetrates the boss 2. The copper alloy is tin-lead bronze CuSn7Pb15. The pre-treatment is cleaning with an alkaline cleaning agent. The composition of the alkaline cleaning agent includes The method comprises the following steps: comprising triethanolamine, citric acid and sodium laureth sulfate in a mass ratio of 4:0.5:1, the total concentration of the alkaline cleaning agent is 1.5wt%, the cleaning temperature is 55°C, the cleaning time is 22 minutes, and then the two are placed together in a melting and casting device for heating and insulation. The melting and casting device includes a melting and casting furnace. After the copper alloy is placed in a molten pool tank of a steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The first stage is heated at a temperature of 980°C and a insulation time of 60 minutes. The second stage is heated at a temperature of 1035°C and a insulation time of 55 minutes.

[0102] (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen gas, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 0.13V. The nitrogen pressure during the second stage of cooling was 1500 mbar, the fan speed was 900 rpm, and the cooling time was 5 s. The nitrogen pressure during the second stage of cooling was 2000 mbar, the fan speed was 1800 rpm, and the cooling time was 3 s. The nitrogen pressure during the third stage of cooling was 2500 mbar, the fan speed was 2700 rpm, and the cooling time was 5 s. After the third stage of cooling, the molten copper alloy had solidified and the cylinder temperature was 910° C. The cooling rate of the fourth stage of cooling was 4° C. / s, the nitrogen pressure was 9000 mbar, the fan speed was 2800 rpm, and the cooling end temperature was 78° C. Then the cylinder was removed and continued to be air-cooled to room temperature.

[0103] (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 620°C and the holding time is 130 minutes. The cooling method after the tempering treatment is to cool to 14°C in the furnace and then take it out of the furnace and air-cool it to room temperature to obtain a copper-steel dual alloy cylinder body.

[0104] In this embodiment, the prepared copper-steel bimetallic cylinder body was subjected to metallographic structure observation using an optical microscope. The shrinkage in the copper layer was all concentrated at the central boss, while the remaining parts were dense and shrinkage-free. The mechanical properties of the cylinder body were tested under the same testing conditions as in Example 1. The hardness of the steel matrix in the cylinder body was 253~293 HBW2.5 / 187.5, the core tensile strength was 878MPa, the impact energy was 90J, and the hardness of the copper layer was 89 HBW2.5 / 62.5.

[0105] Comparative Example 1:

[0106] This comparative example provides a method for melting and casting a copper-steel bimetallic cylinder body. The melting and casting method refers to the method in Example 1, except that the blowing direction of the second stage cooling in step (2) is also vertical to the bottom of the steel substrate and upward.

[0107] In this comparative example, since the second stage cooling does not directly blow air to cool the copper liquid, the copper liquid solidifies incompletely and the cooling rate is inconsistent within the same time, which easily causes solidification defects and reduces the density of the copper layer. At this time, the shrinkage in the copper layer fails to gather completely at the central boss, and the hardness of the copper layer decreases relatively to 73 HBW2.5 / 62.5. The hardness and tensile strength of the steel matrix do not change.

[0108] Comparative Example 2:

[0109] This comparative example provides a method for melting and casting a copper-steel bimetallic cylinder body. The melting and casting method refers to the method in Example 1, except that: step (2) does not include the third stage cooling, and the original third stage cooling time is added to the second stage cooling.

[0110] In this comparative example, since the third stage cooling is not set separately, the second stage cooling time is extended, which prolongs the direct purging time of the copper layer. At this time, the solidification process of the copper liquid is accelerated, especially the heat storage capacity of the boss is reduced, so that defects such as solidification shrinkage cannot be completely gathered around the boss, and the density and hardness of the copper layer are reduced, and the hardness is reduced to 75HBW2.5 / 62.5.

[0111] From the above embodiments and comparative examples, it can be seen that, in the process of cylinder casting, the method of the present invention performs multi-stage cooling on the heated cylinder and controls the gas purge direction in different cooling stages, which can not only achieve rapid solidification of the copper liquid, but also avoid the formation of wavy copper liquid, effectively control solidification defects, and obtain a dense copper layer; through the control of the last stage of cooling and tempering process, the matrix structure of the steel matrix is ​​regulated to form tempered bainite, thereby improving the mechanical properties of the cylinder and the yield of the cylinder; the method has a reasonable operation design and high production efficiency, can effectively shorten the processing time, and reduce production costs.

[0112] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed method of the present invention. However, the present invention is not limited to the above-described detailed method, that is, it does not mean that the present invention must rely on the above-described detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the present method, addition of auxiliary steps, selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A method for melting and casting a copper-steel bimetallic cylinder, characterized in that: The melting and casting method comprises the following steps: (1) After pretreatment, the steel matrix and the copper alloy are placed together in a melting and casting device for heating and heat preservation; Step (1) The upper end of the steel substrate is provided with a molten pool groove and a boss, the boss is located in the middle, and the molten pool groove is arranged around the boss; A center hole is provided at the center of the steel base, the center hole being divided into an upper and lower section with different diameters, the diameter of the upper center hole being smaller than the diameter of the lower center hole, and the upper center hole longitudinally passes through the boss; The copper alloy is placed in a molten pool tank of a steel substrate; (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is divided into four stages. The purge direction of the first, third and fourth stages of cooling is from bottom to top, and the purge direction of the second stage of cooling is from top to bottom. After the third stage of cooling, the molten copper alloy has been solidified, and the cylinder temperature at this time is 880~950℃; The cooling medium is liquid nitrogen, and blowing is performed during the process of liquid nitrogen being gasified into nitrogen gas, and the blowing direction of the gas is controlled; The blowing direction during the first stage of cooling is vertical to the bottom of the steel substrate and upward, the nitrogen pressure is 1000-4000 mbar, the fan speed is 800-1200 rpm, and the cooling time is 2-6 seconds; The blowing direction during the second stage of cooling is vertical to the upper end of the steel substrate and downward, the nitrogen pressure is 1000-4000 mbar, the fan speed is 1500-2500 rpm, and the cooling time is 2-6 seconds; The blowing direction during the third stage of cooling is vertical to the bottom surface of the steel substrate and upward, the nitrogen pressure is 1000-4000 mbar, the fan speed is 2500-3500 rpm, and the cooling time is 2-6 seconds; (3) After cooling in step (2), the cylinder body is tempered to obtain a copper-steel dual alloy cylinder body.

2. The melting and casting method according to claim 1, characterized in that: The material of the steel substrate in step (1) is alloy steel, including chromium-molybdenum steel or chromium steel; The chromium-molybdenum steel includes 42CrMoS4 or 30CrMo, and the chromium steel includes 40Cr; The metallographic structure of the 42CrMoS4 is pearlite+ferrite.

3. The melting and casting method according to claim 1, characterized in that: The copper alloy in step (1) includes any one of tin-lead bronze, tin bronze, bismuth bronze, aluminum bronze or silicon bronze, or a combination of at least two thereof; The tin-lead bronze includes CuSn10Pb10 or CuSn7Pb15, and its metallographic structure is α-Cu+spherical rod-shaped Pb.

4. The melting and casting method according to claim 1, characterized in that: The pretreatment of the steel substrate and the copper alloy in step (1) is cleaning with an alkaline cleaning agent; The alkaline cleaning agent comprises amines, organic acids, surfactants and water; The concentration of the alkaline cleaning agent is 1-3 wt %; The cleaning temperature is 50-70° C. and the cleaning time is 20-30 minutes.

5. The melting and casting method according to claim 1, characterized in that: The melting and casting equipment in step (1) includes a melting and casting furnace. After the copper alloy is placed in the molten pool tank of the steel substrate, the copper alloy and the steel substrate are placed together in the melting and casting furnace. The heating in step (1) is divided into two stages, the heating temperature in the first stage is 790-980°C, and the heating temperature in the second stage is 1020-1040°C; The holding time of the first stage heating is 60-100 minutes, and the holding time of the second stage heating is 50-80 minutes.

6. The melting and casting method according to claim 1, characterized in that: The cooling in step (2) is carried out in a cooling furnace, and the heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace; The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the rotation speed of the fans.

7. The melting and casting method according to claim 6, characterized in that: The blowing direction during the fourth stage cooling in step (2) is vertical to the bottom of the steel substrate and upward, and the liquid nitrogen flow rate is increased for rapid cooling, and the cooling rate is 1.2~5℃ / s; The nitrogen pressure of the fourth stage cooling is 8000-14000 mbar, the fan speed is 2500-3500 rpm, and the cooling end temperature is below 80°C; After the fourth stage of cooling is completed, the cylinder is taken out and air-cooled to room temperature.

8. The melting and casting method according to claim 1, characterized in that: The temperature of the tempering treatment in step (3) is 560-630°C; The holding time of the tempering treatment in step (3) is 120 to 180 minutes; The cooling method after the tempering treatment in step (3) is to directly take it out of the furnace and air-cool it to room temperature, or to cool it in the furnace to below 150°C and then take it out of the furnace and air-cool it to room temperature; The metallographic structure of the steel matrix after the tempering treatment in step (3) is tempered troostite.

9. The melting and casting method according to any one of claims 1 to 8, characterized in that: The melting and casting method comprises the following steps: (1) Pre-treating a steel substrate and a copper alloy, wherein the material of the steel substrate comprises chromium-molybdenum steel or chromium steel, a molten pool groove and a boss are provided at the upper end of the steel substrate, the boss is located in the middle, and the molten pool groove is arranged around the boss, and the copper alloy comprises any one or a combination of at least two of tin-lead bronze, tin bronze, bismuth bronze, aluminum bronze or silicon bronze, and the pre-treatment is performed by cleaning with an alkaline cleaning agent, wherein the composition of the alkaline cleaning agent comprises amines, organic acids, surfactants and water, and the concentration of the alkaline cleaning agent is 1 to 3wt%, the cleaning temperature is 50-70°C, the time is 20-30min, and then they are placed together in a melting and casting equipment for heating and insulation. The melting and casting equipment includes a melting and casting furnace. After the copper alloy is placed in the molten pool tank of the steel substrate, the two are placed together in the melting and casting furnace. The heating is divided into two stages. The temperature of the first stage is 790-980°C, the insulation time is 60-100min, and the temperature of the second stage is 1020-1040°C, and the insulation time is 50-80min. (2) After the heating and heat preservation in step (1) are completed, cooling is performed. The cooling is performed in a cooling furnace. The heated steel substrate and molten copper liquid are transferred from the melting furnace to the cooling furnace. The cooling is divided into four stages. The cooling medium used is liquid nitrogen. Blowing is performed during the process of liquid nitrogen being gasified into nitrogen, and the blowing direction of the gas is controlled. The blowing direction is achieved by fans arranged at the top and bottom of the cooling furnace, and the gas flow rate is controlled by the speed of the fan. The blowing direction of the cooling in the first, third and fourth stages is vertical to the bottom of the steel substrate upward, and the blowing direction of the cooling in the second stage is vertical to the upper end of the steel substrate downward. The nitrogen pressure during the first stage cooling is 1000~4000mbar, and the fan speed is 800~1200r pm, the cooling time is 2~6s, the nitrogen pressure during the second stage cooling is 1000~4000mbar, the fan speed is 1500~2500rpm, and the cooling time is 2~6s. The nitrogen pressure during the third stage cooling is 1000~4000mbar, the fan speed is 2500~3500rpm, and the cooling time is 2~6s. After the third stage cooling, the molten copper alloy has been solidified, and the cylinder temperature at this time is 880~950℃; the cooling rate of the fourth stage cooling is 1.2~5℃ / s, the nitrogen pressure is 8000~14000mbar, the fan speed is 2500~3500rpm, and the cooling end temperature is below 80℃, then the cylinder is removed and continued to air cool to room temperature; (3) After the cooling in step (2) is completed, a tempering treatment is performed. The tempering treatment temperature is 560-630°C, and the holding time is 120-180 min. The cooling method after the tempering treatment is to directly take the cylinder out of the furnace and air-cool to room temperature or to cool the cylinder in the furnace to below 150°C and then take the cylinder out of the furnace and air-cool to room temperature to obtain a copper-steel dual alloy cylinder body. The metallographic structure of the steel matrix after the tempering treatment is tempered bainite.

Images