Method for casting copper alloy layer in cylinder plunger hole

Abstract

The invention provides a method for casting a copper alloy layer in a plunger hole of a cylinder body. The method comprises the following steps: forming a copper melting pool between the periphery of a spline area of a steel substrate blank and the outer wall of the cylinder body; vertically placing the steel substrate blank with the spline area facing upwards and the flow distribution surface facing downwards; plunger steel pins are pressed into plunger holes in the steel base body blank respectively; the copper alloy block is placed in a copper melting pool on the steel base body blank to be sintered and cast; after casting and discharging the steel matrix blank, cooling from bottom to top; continuously cooling until the height of the blackening part of the steel matrix blank accounts for 2 / 3-3 / 4 of the total height, and finishing cooling; and tempering. According to the method, bottom-to-top cooling is adopted, bottom-to-top gradient cooling is formed, the cooling speed of the plunger hole copper alloy layer is slowed down, and cracks of the plunger hole copper alloy layer are avoided. Therefore, the formed plunger hole copper alloy layer has no casting defect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plunger pump, in particular to a method for melting and casting copper alloy layer in cylinder plunger hole. BACKGROUND

[0002] The cylinder is the core component of the plunger pump, and a plurality of plunger holes for reciprocating movement of the plunger are uniformly arranged along the circumference of the cylinder. One end of the cylinder is a smooth end surface that is tightly attached to the distribution plate, which is a distribution surface, and the other end is connected to the transmission shaft through a spline, and the center is a spline area in the form of a protrusion.

[0003] The performance of the plunger hole directly determines the overall service life and reliability of the plunger pump. In order to improve the wear resistance and friction reduction performance of the plunger hole, a layer of copper alloy is generally coated on the inner wall of the plunger hole. In the traditional processing technology, a press machine is usually used to press the copper sleeve into the plunger hole of the steel base at room temperature, and the fixing is achieved through interference fit. However, this process has the following limitations: (1) High processing cost: high-precision processing of the plunger hole is required before pressing to ensure the fit tolerance, increasing the manufacturing cost; (2) Secondary processing requirement: the roundness and straightness of the inner wall of the copper sleeve need to be re-adjusted after pressing, which is a complicated process; (3) Use risk: the copper sleeve is prone to scratches and falling off during long-term operation, affecting the durability of the cylinder, so melting and casting a copper alloy layer directly in the plunger hole has become a common preparation method for high-pressure plunger pumps.

[0004] To overcome the above problems, an integrated preparation method of melting and casting a copper alloy layer directly in the plunger hole has appeared in the prior art. As shown in Figure 7 The copper alloy rod 7 is placed in the plunger hole 1, and the plunger hole plug 8 is used to seal the opening of the plunger hole. After melting and cooling, a layer of copper alloy layer is formed on the inner wall of the plunger hole. Although this method can avoid the defects caused by copper sleeve pressing, the quality of the copper alloy layer depends on the cooling process after melting. The current commonly used cooling processes, such as slow cooling or rapid cooling technology, have corresponding deficiencies: during slow cooling, uneven solidification shrinkage of the copper alloy is prone to cause casting defects such as shrinkage and porosity, reducing the material density; and the rapid cooling process uses water cooling or air cooling, which has a too fast cooling rate, resulting in a large internal stress between the steel base and the copper alloy due to the difference in thermal shrinkage coefficient, and the combined interface of the two is prone to cracking, seriously affecting the bonding strength of the copper layer and the steel base of the plunger hole. SUMMARY

[0005] The purpose of the present application is to provide a method for melting and casting a copper alloy layer in the plunger hole of a cylinder, to solve the problems raised in the background art.

[0006] To achieve the above purpose, the present application provides the following technical solutions: A method for forming a cylinder plunger hole copper alloy layer by melting and casting, comprising the following steps: (1) preparing a steel base body blank of a cylinder, and forming a molten copper pool between the outer periphery of the spline area and the outer wall of the cylinder; (2) vertically placing the steel base body blank with the spline area upward and the flow distribution surface downward; (3) pressing a plunger steel pin into each plunger hole on the steel base body blank; (4) placing a copper alloy block in the molten copper pool on the steel base body blank for sintering and melting and casting; (5) after the steel base body blank is taken out of the furnace, cooling from bottom to top at a cooling rate of 60-90°C per minute; and the cooling is ended when the blackened part of the steel base body blank reaches 2 / 3-3 / 4 of the total height; (6) performing tempering treatment.

[0007] In a further aspect, the plunger steel pin comprises a cylindrical pin body matched with the plunger hole, and a melting and casting gap is left between the outer periphery of the pin body and the inner wall of the plunger hole; the top end of the pin body is fixed with a one-shaped pin head, the length of the pin head is greater than the diameter of the pin body, and the width of the pin head is less than the diameter of the pin body.

[0008] In a further aspect, the sintering and melting and casting is performed under a protective gas, and the temperature is 1000-1200°C and the time is 40-60 min.

[0009] In a further aspect, the tempering treatment is performed at a temperature of 450-650°C.

[0010] In a further aspect, the cooling in step (5) is performed by using a cooling liquid.

[0011] The type of the cooling liquid is not specially limited in the present application, and water, quenching liquid, oil or other cooling liquids can be selected as needed.

[0012] By using the method for forming a cylinder plunger hole copper alloy layer by melting and casting, a copper-steel bimetallic metallurgical diffusion bonding layer without melting and casting defects is formed in the plunger hole, so that the plunger hole has excellent mechanical and tribological properties of the copper alloy layer, thereby improving the service life of the cylinder.

[0013] In the present application, the plunger steel pin is first pressed into the plunger hole, and a melting and casting gap is left between the outer periphery of the pin body of the plunger steel pin and the inner wall of the plunger hole for melting and casting the copper alloy block to form the copper alloy layer. Then the copper alloy block is placed in the molten copper pool for sintering and melting and casting, so that the amount of copper alloy can be reduced and the cost can be reduced.

[0014] In the present application, the spline area of the steel base body blank is inverted and melted and cast with the flow distribution surface downward, so that the welding process of the opening end of the plunger hole can be reduced, and the risk of copper alloy leakage during melting and casting can also be avoided.

[0015] The steel base blank is placed with the flow distribution surface downward for casting the copper alloy, and the plunger hole is not directly contacted with the cooling liquid during the cooling of the steel base blank, so that the cracks in the copper alloy layer in the plunger hole caused by the too fast cooling speed and the poor copper-steel combination are avoided.

[0016] The cooling is from bottom to top, forming a bottom-to-top directional solidification process, which belongs to incomplete cooling, can cause bottom-to-top gradient cooling, slow down the cooling speed of the copper alloy layer in the plunger hole, and avoid the generation of cracks. Thus, the formed copper alloy layer in the plunger hole has no casting defects. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a structure schematic view of the steel base blank in the present application; Figure 2 It is a longitudinal sectional view of Figure 1 ; Figure 3 It is a schematic view after the plunger steel pin is loaded into the steel base blank; Figure 4 It is a longitudinal sectional view of Figure 3 ; Figure 5 It is a structure schematic view of the plunger steel pin; Figure 6 It is a sectional view of the steel base blank in the prior art; Figure 7 It is a schematic view of the assembly of the copper alloy rod, the plunger hole plug and the steel base blank.

[0018] In the figure: 1-plunger hole, 11-casting gap; 2-shaft hole, 3-spline area, 4-flow distribution surface, 5-copper melting pool, 6-plunger steel pin, 61-pin body, 62-pin head, 7-copper alloy rod, 8-plunger hole plug. DETAILED DESCRIPTION

[0019] The specific embodiments of the present application will be further described below in combination with the drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0020] The method for casting a copper alloy layer in a plunger hole of a cylinder body of the present application comprises the following steps: (1) preparing a steel base blank of the cylinder body, such as Figure 1 , 2As shown, the cylinder body is uniformly provided with 9 plunger holes 1 for reciprocating movement of the plunger along its circumference, one end of the cylinder body is a smooth end face closely combined with the distribution disc as a distribution face 4, the other end is a spline region 3 connected with the transmission shaft through splines, and a molten copper pool 5 is formed between the outer periphery of the spline region 3 and the outer wall of the cylinder body. In order to avoid affecting the shaft hole 2 when the plunger hole is molten with copper alloy, the spline region needs to be sealed first. Alternatively, the shaft hole 2 at the center can not be processed when the steel base body blank of the cylinder body is prepared, and the shaft hole 2 is processed after the copper alloy layer is molten on the inner wall of the plunger hole.

[0021] (2) The spline region 3 of the steel base body blank is vertically placed upwards and the distribution face 4 is vertically placed downwards (as shown in Figure 2 ). (3) The plunger steel pin 6 is pressed into each plunger hole 1 on the steel base body blank, as shown in Figure 3 , 4 . The material of the plunger steel pin 6 is steel, and the structure is as shown in Figure 5 , which includes a cylindrical pin body 61 matched with the plunger hole 1, and a molten gap 11 (as shown in Figure 4 ) is left between the outer periphery of the pin body 61 and the inner wall of the plunger hole for molten copper alloy to form a copper alloy layer on the inner wall of the plunger hole 1. The top end of the pin body 61 is fixed with a pin head 62 in the shape of a Chinese character, the length of the pin head 62 is greater than the diameter of the pin body, and the width of the pin head is less than the diameter of the pin body. The plunger steel pin 6 is clamped in the hole of the plunger hole 1 through the pin head 62, which can ensure that the bottom end and the outer periphery form a molten gap 11 with the same size.

[0022] The size of the molten gap 11 is determined according to the thickness of the copper alloy layer to be finally formed. For example, if the thickness of the copper alloy layer is 1-3 mm, the molten gap 11 is 2-7 mm.

[0023] (4) The copper alloy block is placed in the molten copper pool 5 on the steel base body blank for sintering and molten casting; The sintering and molten casting is carried out under a protective gas, and the temperature is 1000-1200℃, and the time is 40-60min.

[0024] (5) After the cylinder body blank is molten out of the furnace, it is cooled from bottom to top at a cooling speed of 60-90℃ per minute; the cooling is ended when the blackened part of the steel base body blank accounts for 2 / 3-3 / 4 of the total height; (6) The cooled steel base body blank is tempered for releasing the internal stress of the steel base body blank, and the temperature of the tempering treatment is 450-650℃.

[0025] The cooling is cooling with a cooling liquid, which can be water, quenching liquid or oil, etc.

[0026] The specific operation can be performed according to the conventional technology in the art, for example, the steel base body blank after melting and casting is placed in a cooling tank containing a cooling liquid, and the bottom of the steel base body blank is kept in contact with the cooling liquid. Alternatively, the steel base body blank is slowly lowered to be immersed in the cooling liquid after the bottom is in contact with the cooling liquid, but the immersion position does not exceed 1 / 3 of the total height of the steel base body blank. Specifically, a lifting platform, guide rail or other device can be used to realize the slow lowering.

[0027] In order to detect the performance of the plunger hole of the cylinder block prepared by the method of the present application, the cylinder block is prepared according to the above-mentioned different and specific process parameters, and the specific implementation is as follows: Example 1: (1) The steel base body blank of the cylinder block is prepared, and a molten copper pool is formed between the outer periphery of the spline area and the outer wall of the cylinder block; (2) The steel base body blank is vertically placed with the spline area upward and the flow distribution surface downward; (3) The plunger steel pin is pressed into each plunger hole on the steel base body blank by using a hydraulic machine; (4) The copper alloy block is placed in the molten copper pool on the steel base body blank, and is placed in a high-temperature furnace by an automatic device for sintering and melting casting; the sintering and melting casting is performed under a protective gas, and the temperature is 1000℃ and the time is 60min.

[0028] (5) After the steel base body blank is melted and cast out of the furnace, water is used as the cooling liquid to cool from bottom to top at a cooling speed of 60℃ per minute; the cooling is ended when the height of the blackened part of the steel base body blank accounts for 3 / 4 of the total height; (6) Tempering is performed at 450℃.

[0029] Example 2: (1) The steel base body blank of the cylinder block is prepared, and a molten copper pool is formed between the outer periphery of the spline area and the outer wall of the cylinder block; (2) The steel base body blank is vertically placed with the spline area upward and the flow distribution surface downward; (3) The plunger steel pin is pressed into each plunger hole on the steel base body blank by using a hydraulic machine; (4) The copper alloy block is placed in the molten copper pool on the steel base body blank, and is placed in a high-temperature furnace by an automatic device for sintering and melting casting; the sintering and melting casting is performed under a protective gas, and the temperature is 1200℃ and the time is 40min.

[0030] (5) After the steel base blank is melted and cast out of the furnace, water is used as the cooling liquid to cool from bottom to top at a cooling rate of 90°C per minute; the cooling is continued until the height of the blackened part of the steel base blank accounts for 2 / 3 of the total height, and then the cooling is ended; (6) Tempering treatment is performed at 650°C.

[0031] Example 3: (1) A steel base blank of a cylinder body is prepared, and a molten copper pool is formed between the outer periphery of the spline area and the outer wall of the cylinder body; (2) The steel base blank is vertically placed with the spline area upward and the flow distribution surface downward; (3) A hydraulic machine is used to press the plunger steel pins into the respective plunger holes on the steel base blank; (4) The copper alloy block is placed in the molten copper pool on the steel base blank, and is put into a high-temperature furnace by an automatic device for sintering and melting; the sintering and melting is performed under a protective gas, and the temperature is 1100°C and the time is 50 min.

[0032] (5) After the steel base blank is melted and cast out of the furnace, water is used as the cooling liquid to cool from bottom to top at a cooling rate of 80°C per minute; the cooling is continued until the height of the blackened part of the steel base blank accounts for 3 / 4 of the total height, and then the cooling is ended; (6) Tempering treatment is performed at 550°C.

[0033] Comparative Example 1: (1) A steel base blank of a cylinder body is prepared, and a molten copper pool is formed between the outer periphery of the spline area and the outer wall of the cylinder body; (2) The steel base blank is vertically placed with the spline area upward and the flow distribution surface downward; (3) A hydraulic machine is used to press the plunger steel pins into the respective plunger holes on the steel base blank; (4) The copper alloy block is placed in the molten copper pool on the steel base blank, and is put into a high-temperature furnace by an automatic device for sintering and melting; the sintering and melting is performed under a protective gas, and the temperature is 1000°C and the time is 60 min.

[0034] (5) After the steel base blank is melted and cast out of the furnace, it is allowed to stand until the surface of the cylinder base blank is completely blackened, and then the cooling is ended; (6) Tempering treatment is performed at 450°C.

[0035] Comparative Example 2: (1) A steel base blank of a cylinder body is prepared, as shown in Figure 6 Fig. 1, the smooth end surface of one end of the cylinder body closely combined with the flow distribution disc is a flow distribution surface 4, the other end is connected with a transmission shaft through splines, and the spline area 3 in the center is convex; (2) vertically place the steel base blank with the flow distribution surface 4 facing upwards and the spline area 3 facing downwards; (3) process a copper alloy rod 7 with a size that exactly matches the inner diameter of the plunger hole 1, and press it into each plunger hole 1 after cleaning; Then use a hydraulic machine to press the plunger hole plug 8 into the hole mouth of the plunger hole in sequence, and then weld the outer periphery of the plunger hole plug 8 and the edge of the steel base blank to seal, so as to prevent copper alloy from leaking during subsequent melting and casting (see Figure 7 ); (4) place in a high-temperature furnace for sintering and melting by an automatic device; the sintering and melting is carried out under a protective gas, the temperature is 1000℃, and the time is 60min.

[0036] (5) after the steel base blank is taken out of the furnace, use water as a cooling liquid to cool from bottom to top at a cooling speed of 60℃ per minute; continue cooling until the steel base blank is black to a height of 3 / 4 of the total height, and then stop cooling; (6) adopt 450℃ for tempering treatment.

[0037] Quality detection is performed on the copper alloy layer of the plunger hole of the cylinder prepared in Examples 1, 2, and 3 and Comparative Examples 1 and 2. The detection includes whether the copper alloy layer has cracks, whether the copper alloy layer and the steel base joint have cracks, and whether the copper alloy layer has sand holes (all can be observed by visual inspection).

[0038] Table 1 Quality detection results of the copper alloy layer of the plunger hole of the cylinder prepared in each example and comparative example

[0039] From the above detection results, it can be seen that: The plunger hole of the cylinder prepared in Examples 1-3 has no cracks in the copper alloy layer, no cracks in the copper alloy layer and the steel base joint, and no sand holes in the copper alloy layer, which meets the requirements.

[0040] However, the copper alloy layer of the plunger hole of the cylinder prepared in Comparative Example 1 has sand holes, which is due to the fact that the steel base blank is placed after being taken out of the furnace in Comparative Example 1 until the surface of the cylinder base blank is completely black, and the copper alloy solidification shrinkage is uneven, which reduces the material density and causes sand hole defects, which cannot meet the technical requirements of the cylinder.

[0041] The copper alloy layer of the plunger hole of the cylinder prepared in Comparative Example 2 has cracks, and the copper alloy layer and the steel base joint have cracks. This is because the steel base blank is vertically placed with the flow distribution surface facing upwards and the spline area facing downwards in Comparative Example 2. When cooling, the plunger hole mouth will first contact the cooling liquid, and the cooling speed is too fast, which will cause cracks in the copper alloy layer of the plunger hole and poor copper-steel joint.

[0042] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of a particular application, and variations of that description can be presented in the context of other applications. Therefore, the scope of the application is not intended to be limited to the described embodiments, but is intended to include all modifications and alternatives coming within the scope of the application.

Claims

1. A method for melting and casting a copper alloy layer in a cylinder block plunger bore, characterized in that: Includes the following steps: (1) Prepare a steel base blank for the cylinder body and form a molten copper pool between the outer periphery of the spline area and the outer wall of the cylinder body; (2) Place the steel substrate blank vertically with the spline area facing up and the flow distribution surface facing down; (3) Press the plunger pins into the plunger holes on the steel substrate blank respectively; (4) Place the copper alloy block in the molten copper pool on the steel substrate blank for sintering and casting; (5) After the steel substrate billet is melted and cast out of the furnace, it is cooled from bottom to top at a cooling rate of 60-90°C per minute; the cooling is stopped when the height of the blackened part of the steel substrate billet accounts for 2 / 3-3 / 4 of the total height. (6) Perform tempering treatment.

2. The method according to claim 1, characterized in that: The plunger pin includes a cylindrical pin body that matches the plunger bore, with a casting gap between the outer periphery of the pin body and the inner wall of the plunger bore; the top of the pin body is fixed with a T-shaped pin head, the length of which is greater than the diameter of the pin body and the width of which is less than the diameter of the pin body.

3. The method according to claim 1, characterized in that: The sintering and casting are carried out under a protective gas at a temperature of 1000-1200℃ for 40-60 minutes.

4. The method according to claim 1, characterized in that: The tempering temperature is 450-650℃.

5. The method according to claim 1, characterized in that: The cooling described in step (5) is performed using a coolant.

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