Fusion casting method for improving quality consistency of copper-steel double-metal cylinder body

Abstract

The invention provides a casting method for improving the quality consistency of a copper-steel double-metal cylinder body, and belongs to the technical field of pump body part machining.The casting method comprises the steps that a plurality of sets of steel matrixes and copper alloy are evenly put into casting equipment to be heated and cast till heat preservation is finished; the heating comprises two stages of heating and heat preservation; and after heat preservation is finished, cooling is conducted, and the copper-steel bimetal cylinder body is obtained. According to the method disclosed by the invention, when a plurality of cylinder bodies are simultaneously cast and processed, the liquid time difference between the inner-layer cylinder body and the outer-layer cylinder body is greatly reduced by dividing the heating stages and particularly controlling the heating temperature of the first stage to be below the liquidus temperature of a copper alloy; when the second-stage heating is carried out, different cylinder bodies are located at the same temperature starting point again, the difference of temperature equalization time of the cylinder bodies in the temperature rising process is reduced, the uniformity of casting quality between the cylinder bodies is effectively improved, and the qualified rate of product machining is increased; the method is simple and convenient to operate, reasonable in design, high in production efficiency, low in production cost and wide in application range.

Description

Technical Field

[0001] The present invention belongs to the technical field of pump body part processing, and relates to a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinders. Background Art

[0002] As one of the most widely used metal materials at present, steel can form different types of composite materials by combining with different materials. For example, the combination of steel and copper and copper alloys can obtain copper-steel composite materials. Based on the properties of steel materials, it also has the ductility, antifriction property, electrical conductivity and thermal conductivity of copper itself. The two complement each other and have good application prospects. Copper-steel bimetallic composite materials can be widely used in wear-resistant and impact-resistant application scenarios. A typical application scenario is for hydraulic cylinder bodies. As one of the key core parts of a plunger pump, the performance and quality of the cylinder body will directly affect the transmission efficiency and service life of the plunger pump.

[0003] Currently, one of the common methods for producing copper-steel bimetallic cylinders is the melting and casting method. This method uses steel materials as the matrix. First, a molten pool groove is processed, and then the copper alloy is placed in the molten pool groove. Utilizing the melting point difference between copper and steel, it is placed in a heating furnace to make the copper cladding on the surface of the steel matrix. After cooling, a bimetallic cylinder is formed, which has the advantages of high production efficiency and low production cost. When melting and casting copper-steel bimetallic cylinders, the melting furnace or heating furnace used is usually a box furnace. A certain number of cylinders are distributed and placed on trays. Due to different placement positions, there are temperature differences between the cylinders. Generally, the heating rate of the outer cylinders is greater than that of the inner cylinders, so that the outer cylinders are in a high-temperature state for a longer time than the inner cylinders, which further leads to differences in the tissue properties between the inner and outer cylinders. Especially, this heating process includes the melting and solidification processes of the copper alloy, which is likely to affect the microscopic properties of the copper alloy, resulting in inconsistent quality of the cylinders in the same batch.

[0004] CN 110434315 A discloses a heating and cooling method for the melting and casting of a steel-copper bimetallic cylinder block. The method includes surface treatment of the steel matrix for melting and casting, preheating, staged heating, variable-speed cooling, and auxiliary crystallization steps. The preheating and staged heating steps include: conveying the steel matrix and copper alloy to the preheating zone in the melting furnace, with the preheating temperature being 800 - 950 °C, and then moving it to the heating zone for staged heating and heat preservation. The staged heating is divided into three stages. The heating temperature in the first stage is 900 - 1050 °C, the heating temperature in the second stage is 1050 - 1150 °C, and the heating temperature in the third stage is 1050 - 1120 °C. Finally, variable-speed cooling is carried out, and the variable-speed cooling is achieved through different cooling media or combinations, including rapid cooling, medium-speed cooling, slow cooling, etc. The key point of this patent is to install a cap to form a temperature gradient in the copper liquid, so that the solidification of the copper liquid preferentially occurs at the interface. However, it does not consider the temperature difference between cylinder blocks during the heating of multiple cylinder blocks, and is only applicable to the case of a single cylinder block. Moreover, the heating temperature in the first stage has exceeded the liquidus temperature of the copper alloy, and it is impossible to optimize the temperature difference between different cylinder blocks.

[0005] CN 116124820 A discloses a copper-steel bimetallic melting and casting experiment method. The method includes: placing a copper-lead alloy test block in a crucible made of alloy steel, and then using a high-temperature confocal laser microscope to conduct a melting and casting experiment on the copper-lead alloy test block. The melting and casting experiment successively includes a first heating stage, a second heating stage, and a solidification stage. The end temperature of the first heating stage is 1060 - 1100 °C, the heat preservation temperature of the second heating stage is 1000 °C, and the average cooling rate in the solidification stage is above 30 °C / s. The temperature in the first stage of the melting and casting experiment in this method is still above the liquidus temperature of the copper-lead alloy, and it is also not applicable to the situation of simultaneous processing of multiple cylinder blocks, nor does it consider how to control when there is a temperature difference between different cylinder blocks.

[0006] In summary, for the control of the quality consistency during the melting and casting process of multiple copper-steel bimetallic cylinder blocks, it is necessary to adjust the temperature in different stages during heating according to the distribution of the temperature difference between different cylinder blocks, reduce the time for the average temperature of different cylinder blocks to reach equilibrium, avoid the tissue difference in different cylinder blocks, and improve the uniformity of the melting and casting quality between cylinder blocks. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks. During the simultaneous melting and casting process of multiple cylinder blocks, through the division of the heating stage, especially by controlling the temperature in the first heating stage below the liquidus temperature of the copper alloy, the time difference of the liquid state time and the time to reach the average temperature between the inner and outer layer cylinder blocks is reduced, the consistency and uniformity of the melting and casting quality between cylinder blocks are improved, and the qualified rate of the melting and casting products is increased.

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

[0009] The present invention provides a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks. The melting and casting method includes the following steps:

[0010] (1) Put several groups of steel substrates and copper alloys evenly into the melting and casting equipment, set the heating program for heating and melting, and keep warm until the end; the heating program includes two-stage heating and heat preservation. The end temperature of the first-stage heating is 810-880°C, such as 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C or 880°C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0011] (2) After the heat preservation in step (1) is completed, cool to obtain a copper-steel bimetallic cylinder block.

[0012] In the present invention, for the melting and casting of copper-steel bimetallic cylinder blocks, when processing multiple cylinder blocks in the same batch, according to their different placement positions, they can be divided into inner-layer and outer-layer cylinder blocks. Since the heating of the inner and outer-layer cylinder blocks has a sequential order, the present invention controls the heating process to reduce the temperature difference between different cylinder blocks. The present invention divides the heating and melting process into two-stage heating and heat preservation. By controlling the end temperature of the first-stage heating below the liquidus temperature of the copper alloy and keeping warm before the copper alloy is completely melted, the difference in the liquid state time between the inner and outer-layer cylinder blocks is greatly reduced, and the difference in the matrix structure caused by different liquid state times is avoided; when performing the second-stage heating and heat preservation, different cylinder blocks are at the same temperature starting point again, reducing the difference in the temperature equalization time of the cylinder blocks during the subsequent heating process, effectively improving the uniformity of the melting and casting quality between the cylinder blocks, and improving the qualification rate of the cylinder block products; the method is simple to operate, reasonable in design, high in production efficiency, low in production cost, and wide in application range.

[0013] The following are the preferred technical solutions of the present invention, but not the limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical purposes and beneficial effects of the present invention can be better achieved and realized.

[0014] 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.

[0015] Preferably, the chromium molybdenum steel includes 42CrMoS4, and the chromium steel includes 40Cr or 42Cr.

[0016] In the present invention, according to the selection of the material of the steel substrate, its austenitizing temperature is above 880°C. Therefore, the heating and heat preservation in the first stage will not cause phase transformation of the copper matrix material of the cylinder block, thus not causing tissue differences.

[0017] As a preferred technical solution of the present invention, the copper alloy in step (1) includes any one or a combination of at least two of tin-lead bronze, aluminum bronze, tin bronze or bismuth bronze. Typical but non-limiting examples of the combination are: a combination of tin-lead bronze and aluminum bronze, a combination of aluminum bronze and tin bronze, a combination of tin-lead bronze, aluminum bronze and tin bronze, a combination of aluminum bronze, tin bronze and bismuth bronze, etc.

[0018] Preferably, the tin-lead bronze includes CuSn10Pb10 or CuSn7Pb15.

[0019] In the present invention, the copper alloy used for cylinder block casting is usually a tin-lead alloy of copper. Its solidus and liquidus temperatures gradually decrease as the content of the tin-lead alloy increases, and the solid-liquid temperature range is relatively wide. Taking CuSn10Pb10 as an example, its solidus temperature is 790 °C and its liquidus temperature is 880 °C. Therefore, when using a box furnace for casting, it is not necessary to adopt too high a casting temperature, otherwise it will only increase the time for the cylinder blocks to reach uniform temperature, and seriously, it will cause grain coarsening and abnormal growth of the outer layer of the cylinder block steel part.

[0020] Preferably, the copper alloy is placed in the molten pool groove of the steel matrix to form a group of cylinder blocks to be processed.

[0021] As a preferred technical solution of the present invention, the steel matrix and the copper alloy in step (1) are cleaned and dried before being put into the casting equipment.

[0022] Preferably, the cleaning is carried out in a cleaning machine.

[0023] Preferably, the temperature of the cleaning is 50-70 °C, such as 50 °C, 52 °C, 55 °C, 58 °C, 60 °C, 62 °C, 65 °C, 68 °C or 70 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; the time is 20-30 min, such as 20 min, 22 min, 24 min, 25 min, 27 min, 28 min or 30 min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, the temperature of the drying is 60-80 °C, such as 60 °C, 62 °C, 65 °C, 68 °C, 70 °C, 72 °C, 75 °C, 78 °C or 80 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; the time is 10-20 min, such as 10 min, 12 min, 14 min, 15 min, 16 min, 18 min or 20 min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In the present invention, the time used for drying is relatively short, and at this time, the blowing and drying method can be adopted to improve the drying rate.

[0026] As a preferred technical solution of the present invention, the melting and casting equipment in step (1) includes a box furnace, and several groups of steel substrates and copper alloys are placed on the tooling racks in the box furnace.

[0027] Preferably, the steel substrates are evenly placed on the tooling racks in the manner of horizontal and vertical arrays. Under the condition of a certain box furnace size, the number of the steel substrates varies according to the different sizes of the steel substrates.

[0028] Preferably, the distance between adjacent steel substrates is 0.5 - 2 cm, such as 0.5 cm, 0.8 cm, 1 cm, 1.2 cm, 1.5 cm, 1.8 cm or 2 cm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] As a preferred technical solution of the present invention, the heat preservation time after the first-stage heating in step (1) is 50 - 70 min, such as 50 min, 52 min, 55 min, 58 min, 60 min, 62 min, 65 min, 68 min or 70 min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In the present invention, the copper alloy is heat-preserved after the first-stage heating, and this temperature is within the solid-liquid phase line temperature range. During this range, the cylinder block is subjected to temperature equalization treatment. The copper block undergoes partial melting and is in a semi-solid state with high viscosity and poor fluidity, and will not fill the molten copper pool in the steel substrate, ensuring that there is no difference in liquid state time at this time.

[0031] Preferably, the heating rate of the first-stage heating is 30 - 50 °C / min, such as 30 °C / min, 32 °C / min, 35 °C / min, 38 °C / min, 40 °C / min, 42 °C / min, 45 °C / min, 48 °C / min or 50 °C / min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0032] In the present invention, during the first-stage heating process, when the copper alloy is heated above the solidus temperature, local melting starts to occur, and at the same time, a peritectic reaction occurs. The Pb phase generates a single liquid phase with the surrounding copper liquid. During the subsequent heat preservation process, the liquid volume fraction of the copper block gradually increases, and at the same time, the peritectic reaction continues, and Pb dissolves in the surrounding liquid copper. On the other hand, partial austenite transformation occurs in the initial structure of the steel substrate.

[0033] Preferably, a protective gas is introduced during the heating and melting and casting process in step (1) to maintain a non-oxidizing atmosphere.

[0034] In the present invention, in order to avoid the reaction between components such as oxygen and metal components during the melting and casting of the cylinder block, the box furnace needs to be evacuated and filled with a protective gas before heating and melting. The protective gas can be selected from nitrogen, inert gases, etc., and a non-oxidizing atmosphere is maintained during the heating and melting process to avoid the oxidation of the copper layer and the steel substrate.

[0035] As a preferred technical solution of the present invention, the end temperature of the second-stage heating is 1020 - 1040 °C, such as 1020 °C, 1022 °C, 1025 °C, 1028 °C, 1030 °C, 1032 °C, 1035 °C, 1038 °C or 1040 °C, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; the holding time after the second-stage heating is 30 - 40 min, such as 30 min, 32 min, 34 min, 35 min, 36 min, 38 min or 40 min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] Preferably, the heating rate of the second-stage heating is 5 - 8 °C / min, such as 5 °C / min, 5.5 °C / min, 6 °C / min, 6.5 °C / min, 7 °C / min, 7.5 °C / min or 8 °C / min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In the present invention, during the second-stage heating and holding process, the copper block further melts until it is completely melted, and the uniformity of the liquid components is further increased, and the steel substrate is completely austenitized.

[0038] As a preferred technical solution of the present invention, the cooling in step (2) is carried out in the cooling chamber of the melting and casting equipment, and the heated steel substrate and molten copper liquid are jointly transferred from the melting furnace to the cooling chamber.

[0039] Preferably, the cooling method in step (2) includes any one or a combination of at least two of natural cooling, gas medium cooling or liquid medium cooling. Typical but non-limiting examples of the combination are: the combination of natural cooling and gas medium cooling, the combination of gas medium cooling and liquid medium cooling, the combination of natural cooling, gas medium cooling and liquid medium cooling, etc.

[0040] Preferably, the gas medium includes nitrogen and / or inert gas, and the liquid medium includes water or coolant.

[0041] Preferably, when the cylinder block is cooled to below 150°C, such as 150°C, 145°C, 140°C, 135°C, 130°C, 125°C, 120°C, 110°C or 100°C, etc., but not limited to the listed values, other unlisted values within this numerical range are equally applicable. After being taken out of the furnace, it is air-cooled until it is cooled to room temperature.

[0042] In the present invention, the cylinder block is cooled and transformed from an austenite state to a low-temperature stable phase structure.

[0043] As a preferred technical solution of the present invention, after the cooling in step (2) is completed, the cylinder block is further subjected to tempering treatment.

[0044] Preferably, the temperature of the tempering treatment is 560 - 630°C, such as 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C or 630°C, etc., but not limited to the listed values, other unlisted values within this numerical range are equally applicable.

[0045] Preferably, the holding time of the tempering treatment is 120 - 180 min, such as 120 min, 130 min, 140 min, 150 min, 160 min, 170 min or 180 min, etc., but not limited to the listed values, other unlisted values within this numerical range are equally applicable.

[0046] Preferably, the cooling method after the tempering treatment is air-cooling until it is cooled to room temperature.

[0047] Preferably, the metallographic structure of the steel matrix after the tempering treatment is tempered sorbite.

[0048] In the present invention, through cooling and tempering treatment, the metallographic structure of the steel matrix can be transformed into tempered sorbite, which has excellent strength and toughness and excellent mechanical properties. This is required based on the application of the cylinder block. As a key component in a piston pump or motor, the dual-metal cylinder block functions to form a sealed volume in cooperation with the piston and the valve plate to achieve the purpose of suction and oil discharge to provide power. During service, it is subjected to impact and friction, so it needs to have good strength and excellent fatigue resistance.

[0049] As a preferred technical solution of the present invention, the casting method includes the following steps:

[0050] (1) Put several groups of steel substrates and copper alloys evenly into the melting and casting equipment. The material of the steel substrate includes chromium molybdenum steel or chromium steel, and the copper alloy includes any one or a combination of at least two of tin-lead bronze, aluminum bronze, tin bronze, or bismuth bronze. Before putting the steel substrate and copper alloy into the melting and casting equipment, they are first cleaned and dried. The cleaning temperature is 50-70°C, and the time is 20-30 min. The drying temperature is 60-80°C, and the time is 10-20 min. The melting and casting equipment includes a box furnace. Several groups of steel substrates and copper alloys are evenly placed on the tooling rack in the box furnace in a horizontal and vertical array manner. The distance between adjacent steel substrates is 0.5-2 cm. Set the heating program to heat and melt-cast until the heat preservation ends. The heating program includes two-stage heating and heat preservation. During the heating and melting-casting process, a protective gas is introduced to maintain a non-oxidizing atmosphere. The end temperature of the first-stage heating is 810-880°C, the heat preservation time is 50-70 min, and the heating rate is 30-50°C / min. The end temperature of the second-stage heating is 1020-1040°C, the heat preservation time is 30-40 min, and the heating rate is 5-8°C / min.

[0051] (2) After the heat preservation in step (1) ends, cooling is carried out. The cooling is carried out in the cooling chamber of the melting and casting equipment. The heated steel substrate and molten copper liquid are jointly transferred to the cooling chamber. The cooling method includes any one or a combination of at least two of natural cooling, gas medium cooling, or liquid medium cooling. When the cylinder body is cooled to below 150°C, it is taken out of the furnace for air cooling until it is cooled to room temperature. After the cooling ends, the cylinder body is then subjected to tempering treatment. The tempering treatment temperature is 560-630°C, and the heat preservation time is 120-180 min. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature, and a copper-steel bimetal cylinder body is obtained. The metallographic structure of the steel substrate after the tempering treatment is tempered sorbite.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) In the method of the present invention during the simultaneous melting and casting process of multiple cylinder bodies, through the division of the heating stage, especially by controlling the temperature of the first-stage heating below the liquidus temperature of the copper alloy and carrying out heat preservation before the copper alloy is completely melted, the difference in the liquid time between the inner and outer layer cylinder bodies is greatly reduced.

[0054] (2) When the method of the present invention undergoes the first-stage heating and heat preservation, and then the second-stage heating and heat preservation, different cylinder bodies are re-in the same temperature starting point, reducing the difference in the equalization time of the cylinder bodies during the subsequent heating process, effectively improving the uniformity and consistency of the melting and casting quality between the cylinder bodies, and improving the qualified rate of the cylinder body products, which can reach more than 98%.

[0055] (3) The method of the present invention is easy to operate, reasonably designed, with high production efficiency, low production cost, and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is the temperature change curve during the heating and melting casting process of the copper-steel bimetallic cylinder block provided in Embodiment 1 of the present invention;

[0057] Figure 2 It is the metallographic structure of the copper layer in the inner copper-steel bimetallic cylinder block provided in Embodiment 1 of the present invention;

[0058] Figure 3 It is the metallographic structure of the copper layer in the outer copper-steel bimetallic cylinder block provided in Embodiment 1 of the present invention;

[0059] Figure 4 It is the metallographic structure of the steel matrix in the inner copper-steel bimetallic cylinder block provided in Embodiment 1 of the present invention;

[0060] Figure 5 It is the metallographic structure of the steel matrix in the outer copper-steel bimetallic cylinder block provided in Embodiment 1 of the present invention;

[0061] Figure 6 It is the temperature change curve during the heating and melting casting process of the copper-steel bimetallic cylinder block provided in Comparative Example 1 of the present invention;

[0062] Figure 7 It is the metallographic structure of the copper layer in the inner copper-steel bimetallic cylinder block provided in Comparative Example 1 of the present invention;

[0063] Figure 8 It is the metallographic structure of the copper layer in the outer copper-steel bimetallic cylinder block provided in Comparative Example 1 of the present invention;

[0064] Figure 9 It is the metallographic structure of the steel matrix in the inner copper-steel bimetallic cylinder block provided in Comparative Example 1 of the present invention;

[0065] Figure 10 It is the metallographic structure of the steel matrix in the outer copper-steel bimetallic cylinder block provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0066] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of the claimed protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0067] The following are typical but non-limiting embodiments of the present invention:

[0068] Embodiment 1:

[0069] This embodiment provides a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks. The melting and casting method includes the following steps:

[0070] (1) Put several groups of steel substrates and copper alloys evenly into the melting and casting equipment. The material of the steel substrate is chromium molybdenum steel 42CrMoS4, and the copper alloy is tin-lead bronze CuSn10Pb10. Before putting the steel substrate and copper alloy into the melting and casting equipment, they are first cleaned and dried. The temperature of the cleaning is 60 °C, and the time is 25 min. The temperature of the drying is 70 °C, and the time is 15 min. The melting and casting equipment is a box furnace. Arrange 16 groups of steel substrates and copper alloys evenly on the tooling rack in the box furnace in a 4×4 horizontal and vertical array. The distance between adjacent steel substrates is 1 cm. Set the heating program for heating and melting until the heat preservation ends. The temperature change curve during the heating and melting process is as Figure 1 shown. Argon is introduced during the heating and melting process to maintain a non-oxidizing atmosphere. The heating is divided into two stages of heating and heat preservation. The end temperature of the first-stage heating is 840 °C, the heat preservation time is 60 min, and the heating rate is 48 °C / min. The end temperature of the second-stage heating is 1038 °C, the heat preservation time is 40 min, and the heating rate is 6.5 °C / min;

[0071] (2) After the heat preservation in step (1) ends, cooling is carried out. The cooling is carried out in the cooling chamber of the melting and casting equipment. Transfer the heated steel substrate and molten copper liquid together to the cooling chamber. The cooling method is nitrogen purge cooling. When the cylinder block is cooled to 150 °C, it is taken out of the furnace for air cooling until it is cooled to room temperature. After the cooling ends, the cylinder block is subjected to tempering treatment. The temperature of the tempering treatment is 600 °C, and the heat preservation time is 120 min. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature to obtain a copper-steel bimetallic cylinder block.

[0072] In the copper-steel bimetallic cylinder block prepared in this embodiment, select one cylinder block from the inner layer and the outer layer respectively and observe it with an optical microscope. The metallographic structures of the copper layers in the inner cylinder block and the outer cylinder block are respectively as Figure 2 and 3 shown, and the metallographic structures of the steel substrates are respectively as Figure 4 and Figure 5 shown; and the hardness of two copper-steel bimetallic cylinder blocks is detected. The hardness detection uses a Brinell hardness tester, and the detection position is the surface of the copper layer.

[0073] In this embodiment, by Figure 2 and Figure 3It can be seen that the size and distribution of the Pb phase in the copper layers of the inner and outer cylinder blocks have good consistency. The average size of the Pb phase in the copper layer of the inner cylinder block is 25 μm, and the average size of the Pb phase in the copper layer of the outer cylinder block is 30 μm. The hardness of the copper layer of the inner cylinder block is 100 HBW2.5 / 62.5, and the hardness of the copper layer of the outer cylinder block is 101 HBW2.5 / 62.5;

[0074] It can be seen from Figure 4 and Figure 5 that the metallographic structure of the steel matrix of the inner and outer cylinder blocks is tempered sorbite. The hardness of the steel matrix in the inner cylinder block is 273 HBW2.5 / 187.5, and the hardness of the steel matrix in the outer cylinder block is 275 HBW2.5 / 187.5. Thus, it can be known that the performance consistency of the inner and outer cylinder blocks processed by the same batch of melting and casting is good.

[0075] Example 2:

[0076] This embodiment provides a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks. The melting and casting method includes the following steps:

[0077] (1) Put several groups of steel matrices and copper alloys evenly into the melting and casting equipment. The material of the steel matrix is chromium molybdenum steel 42CrMoS4, and the copper alloy is tin-lead bronze CuSn10Pb10. The steel matrix and copper alloy are cleaned and dried before being put into the melting and casting equipment. The cleaning temperature is 70 °C, and the time is 20 min. The drying temperature is 80 °C, and the time is 10 min. The melting and casting equipment is a box furnace. Arrange 16 groups of steel matrices and copper alloys evenly on the tooling rack in the box furnace in a 4×4 horizontal and vertical array. The distance between adjacent steel matrices is 0.5 cm. Set the heating program for heating and melting until the heat preservation ends. Argon is introduced during the heating and melting process to maintain a non-oxidizing atmosphere. The heating is divided into two-stage heating and heat preservation. The end temperature of the first-stage heating is 810 °C, the heat preservation time is 70 min, and the heating rate is 30 °C / min. The end temperature of the second-stage heating is 1030 °C, the heat preservation time is 35 min, and the heating rate is 5 °C / min;

[0078] (2) After the heat preservation in step (1) ends, carry out cooling. The cooling is carried out in the cooling chamber of the melting and casting equipment. Transfer the heated steel matrix and molten copper liquid to the cooling chamber together. The cooling method is water cooling. When the cylinder block is cooled to 140 °C, take it out of the furnace for air cooling until it is cooled to room temperature. After the cooling ends, carry out tempering treatment on the cylinder block. The tempering treatment temperature is 560 °C, and the heat preservation time is 180 min. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature to obtain a copper-steel bimetallic cylinder block.

[0079] In the copper-steel bimetallic cylinder block prepared in this embodiment, one cylinder block is selected from the inner layer and the outer layer respectively for observation with an optical microscope, and the hardness of two copper-steel bimetallic cylinder blocks is detected under the same detection conditions as in Embodiment 1.

[0080] In this embodiment, the size and distribution of the Pb phase in the copper layer of the inner and outer cylinder blocks have good consistency. The average size of the Pb phase in the copper layer of the inner cylinder block is 27 μm, and the average size of the Pb phase in the copper layer of the outer cylinder block is 29 μm; the hardness of the copper layer of the inner cylinder block is 108 HBW2.5 / 62.5, and the hardness of the copper layer of the outer cylinder block is 110 HBW2.5 / 62.5;

[0081] The metallographic structure of the steel matrix of the inner and outer cylinder blocks is tempered sorbite. The hardness of the steel matrix in the inner cylinder block is 282 HBW2.5 / 187.5, and the hardness of the steel matrix in the outer cylinder block is 285 HBW2.5 / 187.5; it can be seen from this that the performance consistency of the inner and outer cylinder blocks processed by the same batch of melting and casting is good.

[0082] Embodiment 3:

[0083] This embodiment provides a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks, and the melting and casting method includes the following steps:

[0084] (1) A number of groups of steel matrices and copper alloys are evenly placed into a melting and casting device. The material of the steel matrix is chromium steel 42Cr, and the copper alloy is tin-lead bronze CuSn10Pb10. Before being put into the melting and casting device, the steel matrix and the copper alloy are first cleaned and dried. The temperature of the cleaning is 50 °C, and the time is 30 min. The temperature of the drying is 60 °C, and the time is 20 min; the melting and casting device is a box furnace. 16 groups of steel matrices and copper alloys are evenly placed on the tooling rack in the box furnace in a 4×4 horizontal and vertical array. The distance between adjacent steel matrices is 1.5 cm; a heating program is set for heating and melting until the heat preservation ends. Nitrogen is introduced during the heating and melting process to maintain a non-oxidizing atmosphere. The heating is divided into two-stage heating and heat preservation. The end temperature of the first-stage heating is 875 °C, the heat preservation time is 50 min, and the heating rate is 40 °C / min. The end temperature of the second-stage heating is 1020 °C, the heat preservation time is 30 min, and the heating rate is 8 °C / min;

[0085] (2)After the heat preservation in step (1) is completed, cooling is carried out. The cooling is carried out in the cooling chamber of the melting and casting equipment. The heated steel matrix and molten copper liquid are jointly transferred to the cooling chamber. The cooling method is first purged and cooled with nitrogen, and then naturally cooled. When the cylinder block is cooled to 130 °C, it is taken out of the furnace for air cooling until it is cooled to room temperature. After the cooling is completed, the cylinder block is subjected to tempering treatment. The temperature of the tempering treatment is 630 °C, and the holding time is 135 min. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature, and a copper-steel bimetallic cylinder block is obtained.

[0086] In the copper-steel bimetallic cylinder block prepared in this embodiment, one cylinder block is selected from the inner layer and the outer layer respectively for observation with an optical microscope, and the hardness of the two copper-steel bimetallic cylinder blocks is detected under the same detection conditions as in Example 1.

[0087] In this embodiment, the size and distribution of the Pb phase in the copper layer of the inner layer and outer layer cylinder blocks are both in good consistency. The average size of the Pb phase in the copper layer of the inner layer cylinder block is 33 μm, and the average size of the Pb phase in the copper layer of the outer layer cylinder block is 35 μm. The hardness of the copper layer of the inner layer cylinder block is 96 HBW2.5 / 62.5, and the hardness of the copper layer of the outer layer cylinder block is 98 HBW2.5 / 62.5;

[0088] The metallographic structure of the steel matrix of the inner layer and outer layer cylinder blocks is tempered sorbite. The hardness of the steel matrix in the inner layer cylinder block is 284 HBW2.5 / 187.5, and the hardness of the steel matrix in the outer layer cylinder block is 288 HBW2.5 / 187.5. It can be seen that the performance consistency of the inner layer and outer layer cylinder blocks processed by the same batch of melting and casting is good.

[0089] Example 4:

[0090] This embodiment provides a melting and casting method for improving the quality consistency of a copper-steel bimetallic cylinder block. The melting and casting method includes the following steps:

[0091] (1) Put several groups of steel substrates and copper alloys evenly into a melting and casting device. The material of the steel substrate is chromium steel 40Cr, and the copper alloy is tin-lead bronze CuSn7Pb15. Before putting the steel substrate and copper alloy into the melting and casting device, they are first cleaned and dried. The cleaning temperature is 65 °C and the time is 22 min. The drying temperature is 75 °C and the time is 12 min. The melting and casting device is a box furnace. Arrange 25 groups of steel substrates and copper alloys evenly on the tooling rack in the box furnace in a 5×5 horizontal and vertical array. The distance between adjacent steel substrates is 2 cm. Set the heating program for heating and melting, and until the heat preservation ends. Neon gas is introduced during the heating and melting process to maintain a non-oxidizing atmosphere. The heating is divided into two-stage heating and heat preservation. The end temperature of the first-stage heating is 825 °C, the heat preservation time is 55 min, and the heating rate is 35 °C / min. The end temperature of the second-stage heating is 1025 °C, the heat preservation time is 32 min, and the heating rate is 7 °C / min;

[0092] (2) After the heat preservation in step (1) ends, cooling is carried out. The cooling is carried out in the cooling chamber of the melting and casting device. Transfer the heated steel substrate and molten copper liquid together to the cooling chamber. The cooling method is first water cooling and then natural cooling. When the cylinder body is cooled to 120 °C, it is taken out of the furnace for air cooling until it is cooled to room temperature. After the cooling ends, the cylinder body is subjected to tempering treatment. The tempering treatment temperature is 580 °C and the heat preservation time is 160 min. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature to obtain a copper-steel bimetallic cylinder body.

[0093] In the copper-steel bimetallic cylinder body prepared in this embodiment, select one cylinder body from the innermost layer and the outermost layer respectively for observation with an optical microscope, and perform hardness testing on the two copper-steel bimetallic cylinder bodies. The testing conditions are the same as those in Example 1.

[0094] In this embodiment, the size and distribution of the Pb phase in the copper layer of the inner and outer cylinder bodies have good consistency. The average size of the Pb phase in the copper layer of the inner cylinder body is 33 μm, and the average size of the Pb phase in the copper layer of the outer cylinder body is 35 μm. The hardness of the copper layer of the inner cylinder body is 96 HBW2.5 / 62.5, and the hardness of the copper layer of the outer cylinder body is 98 HBW2.5 / 62.5;

[0095] The metallographic structure of the steel substrate of the inner and outer cylinder bodies is tempered sorbite. The hardness of the steel substrate in the inner cylinder body is 265 HBW2.5 / 187.5, and the hardness of the steel substrate in the outer cylinder body is 270 HBW2.5 / 187.5. It can be seen that the performance consistency of the inner and outer cylinder bodies processed by the same batch of melting and casting is good.

[0096] Example 5:

[0097] This embodiment provides a melting and casting method for improving the quality consistency of copper-steel bimetallic cylinder blocks. The melting and casting method includes the following steps:

[0098] (1) Put several groups of steel substrates and copper alloys evenly into the melting and casting equipment. The material of the steel substrate is chromium molybdenum alloy steel 42CrMoS4, and the copper alloy is tin-lead bronze CuSn7Pb15. Before putting the steel substrate and copper alloy into the melting and casting equipment, they are first cleaned and dried. The temperature of the cleaning is 55°C, and the time is 27 minutes. The temperature of the drying is 65°C, and the time is 18 minutes. The melting and casting equipment is a box furnace. Arrange 25 groups of steel substrates and copper alloys evenly on the tooling rack in the box furnace in a 5×5 horizontal and vertical array. The distance between adjacent steel substrates is 1.2 cm. Set the heating program for heating and melting, and until the heat preservation ends. Argon is introduced during the heating and melting process to maintain a non-oxidizing atmosphere. The heating is divided into two-stage heating and heat preservation. The end temperature of the first-stage heating is 860°C, the heat preservation time is 65 minutes, and the heating rate is 45°C / min. The end temperature of the second-stage heating is 1035°C, the heat preservation time is 38 minutes, and the heating rate is 6°C / min.

[0099] (2) After the heat preservation in step (1) ends, cooling is carried out. The cooling is carried out in the cooling chamber of the melting and casting equipment. Transfer the heated steel substrate and molten copper liquid to the cooling chamber together. The cooling method is first purged and cooled with argon, and then naturally cooled. When the cylinder block is cooled to 135°C, it is taken out of the furnace for air cooling until it is cooled to room temperature. After the cooling ends, the cylinder block is subjected to tempering treatment. The temperature of the tempering treatment is 620°C, and the heat preservation time is 130 minutes. The cooling method after the tempering treatment is air cooling until it is cooled to room temperature, and a copper-steel bimetallic cylinder block is obtained.

[0100] In the copper-steel bimetallic cylinder block prepared in this embodiment, one cylinder block is selected from the innermost layer and the outermost layer respectively for observation with an optical microscope, and hardness tests are carried out on the two copper-steel bimetallic cylinder blocks. The test conditions are the same as those in Example 1.

[0101] In this embodiment, the size and distribution of the Pb phase in the copper layer of the inner and outer cylinder blocks both have good consistency. The average size of the Pb phase in the copper layer of the inner cylinder block is 31 μm, and the average size of the Pb phase in the copper layer of the outer cylinder block is 35 μm. The hardness of the copper layer of the inner cylinder block is 95 HBW2.5 / 62.5, and the hardness of the copper layer of the outer cylinder block is 97 HBW2.5 / 62.5.

[0102] The metallographic structure of the steel matrix of both the inner and outer cylinder blocks is tempered sorbite. The hardness of the steel matrix in the inner cylinder block is 280 HBW2.5 / 187.5, and the hardness of the steel matrix in the outer cylinder block is 285 HBW2.5 / 187.5. It can be seen that the performance consistency of the inner and outer cylinder blocks processed by the same batch of melting and casting is relatively good.

[0103] Comparative Example 1:

[0104] This comparative example provides a melting and casting method for a copper-steel bimetallic cylinder block. The melting and casting method refers to the method in Example 1, except that: the heating in step (1) is not divided into two stages, but is heated to 1038 °C at one time. The temperature change curve during the heating and melting process is as Figure 6 shown, and the holding time is the sum of the holding times of the two stages.

[0105] In the copper-steel bimetallic cylinder block prepared in this comparative example, one cylinder block is selected from the inner and outer layers respectively for observation by an optical microscope. The metallographic structures of the copper layers in the inner and outer cylinder blocks are respectively as Figure 7 and 8 shown, and the metallographic structures of the steel matrix are respectively as Figure 9 and Figure 10 shown; and the hardness of two copper-steel bimetallic cylinder blocks is detected under the same conditions as in Example 1.

[0106] In this comparative example, from Figure 7 and Figure 8 it can be seen that there are obvious differences in the size and distribution of the Pb phase in the copper layers of the inner and outer cylinder blocks. The average size of the Pb phase in the copper layer of the inner cylinder block is 88 μm, and the average size of the Pb phase in the copper layer of the outer cylinder block is 45 μm; the hardness of the copper layer of the inner cylinder block is 89 HBW2.5 / 62.5, and the hardness of the copper layer of the outer cylinder block is 98 HBW2.5 / 62.5;

[0107] From Figure 9 and Figure 10 it can be seen that the metallographic structures of the steel matrix of both the inner and outer cylinder blocks are tempered sorbite. The hardness of the steel matrix in the inner cylinder block is 253 HBW2.5 / 187.5, and the hardness of the steel matrix in the outer cylinder block is 278 HBW2.5 / 187.5. It can be seen that there are differences in the performance of the inner and outer cylinder blocks processed by the same batch of melting and casting, and the consistency is poor.

[0108] As can be seen from the above embodiments and comparative examples, in the process of simultaneous melting and casting of multiple cylinder blocks by the method of the present invention, through the division of the heating stage, especially by controlling the temperature in the first stage of heating to be below the liquidus temperature of the copper alloy and performing heat preservation before the copper alloy is completely melted, the difference in the liquid time between the inner and outer layer cylinder blocks is greatly reduced; when the method is heated and insulated in the first stage and then heated and insulated in the second stage, different cylinder blocks are re-started at the same temperature, reducing the difference in the temperature equalization time of the cylinder blocks during the subsequent heating process, effectively improving the uniformity and consistency of the melting and casting quality between the cylinder blocks, and increasing the qualified rate of the cylinder block product processing, which can reach more than 98%; the method is simple to operate, reasonably designed, has high production efficiency, low production cost, and a wide range of applications.

[0109] The applicant declares that the present invention uses the above embodiments to illustrate the detailed method of the present invention, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent replacement of the method of the present invention, addition of auxiliary steps, selection of specific methods, etc. all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A casting method for improving the quality consistency of a copper-steel bimetallic cylinder, characterized in that: The melting and casting method comprises the following steps: (1) placing several groups of steel matrix and copper alloy uniformly into a melting and casting device, setting a heating program for heating and melting, and ending the heat preservation; the heating program includes two-stage heating and heat preservation, and the end temperature of the first stage heating is 810-880°C; (2) After the heat preservation in step (1) is completed, cooling is performed to obtain a copper-steel bimetallic cylinder.

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 chrome-molybdenum steel or chrome steel; The chromium-molybdenum steel includes 42CrMoS4, and the chromium steel includes 40Cr or 42Cr.

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, aluminum bronze, tin bronze or bismuth bronze, or a combination of at least two thereof; The tin-lead bronze includes CuSn10Pb10 or CuSn7Pb15; The copper alloy is placed in a molten pool tank of a steel matrix to form a group of cylinder bodies to be processed.

4. The melting and casting method according to claim 1, characterized in that: Step (1) The steel substrate and the copper alloy are cleaned and dried before being placed in the melting and casting equipment; The cleaning is carried out in a cleaning machine; The cleaning temperature is 50-70°C and the cleaning time is 20-30 minutes; The drying temperature is 60-80° C. and the drying time is 10-20 min.

5. The melting and casting method according to claim 1, characterized in that: The melting and casting equipment in step (1) includes a box-type furnace, and the plurality of groups of steel substrates and copper alloys are placed on a tooling rack in the box-type furnace; The steel substrates are evenly placed on the tooling frame in a horizontal and vertical array; The distance between adjacent steel substrates is 0.5~2cm.

6. The melting and casting method according to claim 1, characterized in that: Step (1) The holding time after the first stage of heating is 50 to 70 minutes; The heating rate of the first stage heating is 30~50℃ / min; During the heating and casting process in step (1), a protective gas is introduced to maintain a non-oxidizing atmosphere.

7. The melting and casting method according to claim 1, characterized in that: In the heating procedure of step (1), the terminal temperature of the second stage heating is 1020-1040°C, and the holding time after the second stage heating is 30-40 minutes; The heating rate of the second stage heating is 5-8°C / min.

8. The melting and casting method according to claim 1, characterized in that: The cooling in step (2) is carried out in a cooling chamber of the melting and casting equipment, and the heated steel matrix and the molten copper are transferred together into the cooling chamber; The cooling method in step (2) includes any one of natural cooling, gas medium cooling or liquid medium cooling, or a combination of at least two of them; The gaseous medium includes nitrogen and / or an inert gas, and the liquid medium includes water or a coolant; When the cylinder body is cooled to below 150° C., it is taken out of the furnace and air-cooled until it cools to room temperature.

9. The melting and casting method according to claim 1, characterized in that: After the cooling in step (2) is completed, the cylinder body is tempered; The tempering treatment temperature is 560-630°C, and the holding time is 120-180min; The cooling method after the tempering treatment is air cooling until it cools to room temperature; The metallographic structure of the steel matrix after the tempering treatment is tempered troostite.

10. The melting and casting method according to any one of claims 1 to 9, characterized in that: The melting and casting method comprises the following steps: (1) several groups of steel substrates and copper alloys are uniformly placed in a melting and casting device, wherein the material of the steel substrates includes chromium-molybdenum steel or chromium steel, and the copper alloy includes any one of tin-lead bronze, aluminum bronze, tin bronze or bismuth bronze or a combination of at least two thereof. The steel substrates and copper alloys are first cleaned and dried before being placed in the melting and casting device, wherein the cleaning temperature is 50-70°C and the time is 20-30 minutes, and the drying temperature is 60-80°C and the time is 10-20 minutes. The melting and casting device includes a box-type furnace, and several groups of steel substrates and copper alloys are uniformly placed in a horizontal and vertical array. On the tooling rack in the box furnace, the distance between adjacent steel substrates is 0.5~2cm; the heating program is set to heat and cast until the insulation is completed, the heating program includes two-stage heating and insulation, protective gas is introduced during the heating and casting process to maintain a non-oxidizing atmosphere, the terminal temperature of the first stage heating is 810~880℃, the insulation time is 50~70min, and the heating rate is 30~50℃ / min; the terminal temperature of the second stage heating is 1020~1040℃, the insulation time is 30~40min, and the heating rate is 5~8℃ / min; (2) After the insulation in step (1) is completed, cooling is performed, the cooling is performed in a cooling chamber of a melting and casting device, and the heated steel substrate and molten copper are transferred to the cooling chamber together. The cooling method includes any one of natural cooling, gas medium cooling or liquid medium cooling, or a combination of at least two of them. When the cylinder body is cooled to below 150° C., it is taken out of the furnace and air-cooled until it is cooled to room temperature. After the cooling is completed, the cylinder body is tempered, the tempering temperature is 560-630° C., the insulation time is 120-180 min, and the cooling method after the tempering treatment is air cooling until it is cooled to room temperature to obtain a copper-steel bimetallic cylinder body. The metallographic structure of the steel substrate after the tempering treatment is tempered troostite.

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