A large-size hydraulic breaker piston and its manufacturing method

Abstract

The invention discloses a large-size hydraulic breaker hammer piston and a manufacturing method thereof, wherein the large-size hydraulic breaker hammer piston comprises a piston base body made of high-carbon alloy steel 9CrV, and the piston base body is made through a quenching and tempering treatment; a circular countersunk hole is opened on one end surface of the piston base body, and the invention can achieve balanced strength and toughness of the entire cross-section of the large-size hydraulic breaker hammer piston by coordinating with corresponding processing and heat treatment processes, thereby significantly improving the comprehensive strength and toughness of the large-size hydraulic breaker hammer piston.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy machinery manufacturing, and in particular relates to a large-size hydraulic breaker piston and a manufacturing method thereof. Background Art

[0002] As a new type of hydraulic engineering equipment, hydraulic breaker is widely used in the crushing of mine rocks and various large-scale engineering construction. The piston in the impact system of the hydraulic breaker is the key component that directly does work and is also the most critical working component of the hydraulic breaker.

[0003] For a long time, well-known international rock drilling machinery companies such as Atlas have occupied the market. In the existing technology, the pistons in hydraulic breakers are made of low-carbon alloy steel that has been tempered and then surface strengthened (including carburizing, etc.). While their service life is long, their manufacturing cost is also expensive.

[0004] In recent years, China has begun to use high-carbon alloy steels such as GCr15 to manufacture pistons for hydraulic breakers, and has achieved certain market applications.

[0005] However, with the upgrade of hydraulic crushing machinery models, the piston size has gradually increased.

[0006] During field applications, the striking end surface of the piston made of high-carbon alloy steel is prone to collapse and cracking during operation, thereby shortening the service life of the hydraulic breaker.

[0007] The fundamental reason for the above problems is the imbalance between the quenching hardened layer and the internal strength and toughness of high carbon alloy steel.

[0008] To this end, the present invention analyzes the causes of cracking and failure of piston steel, and designs a special structure and a corresponding manufacturing method for a large-sized hydraulic breaker piston in view of the special working environment of the large-sized hydraulic breaker piston; the overall cross-sectional strength and toughness of the large-sized hydraulic breaker piston are balanced, the hardness and toughness mutation phenomenon caused by the size effect is effectively alleviated, and the comprehensive strength and toughness of the large-sized hydraulic breaker piston is significantly improved. Summary of the invention

[0009] The main technical problem to be solved by the present invention is to provide a large-size hydraulic breaker piston and a manufacturing method thereof, wherein the piston structure has the characteristics of balanced overall cross-section strength and toughness and no drastic performance changes.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0011] A large-size hydraulic breaker piston comprises a piston base body made of high-carbon alloy steel 9CrV, the piston base body is made through quenching and tempering treatment; a circular countersunk hole is opened on one end surface of the piston base body.

[0012] The following is a further optimization of the above technical solution by the present invention:

[0013] The surface hardness of the piston is: 57-63HRC; ultrasonic flaw detection ≤ level 2.

[0014] Further optimization: A first transition section, a second transition section and a third transition section which are connected in sequence and integrated are arranged on the outer surface of the piston base body at a position close to an end surface having a circular countersunk hole.

[0015] The present invention also provides a method for preparing the above-mentioned large-size hydraulic breaker piston, the method comprising the machining steps of:

[0016] S1. Cutting: Select high carbon alloy steel 9CrV that is suitable for manufacturing large-size hydraulic breaker pistons for production. The raw materials of 9CrV steel must be inspected before entering the factory;

[0017] S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston to finally obtain a rough product.

[0018] The following is a further optimization of the above technical solution by the present invention:

[0019] The manufacturing method also includes a tempering step:

[0020] T1. Heating: Place the rough product into a heating furnace and heat it to 820-850°C at a heating rate of 5-10°C / min. Maintain a carbon potential protective atmosphere of 0.8-1.1% in the heating furnace and then keep it warm for 5 hours;

[0021] T2, quenching: put the heated and heat-insulated blank product in the air for precooling for 1 minute, and then put it into the quenching medium for quenching after precooling. The quenching time is 2.5-4 minutes. After quenching, the temperature of the blank product is 200-290℃;

[0022] T3, nitrate bath: put the quenched blank product into nitrate bath, where the nitrate bath temperature is 230℃ and the nitrate bath insulation time is 4 hours;

[0023] T4, first low-temperature tempering: The blank product treated with nitrate bath is subjected to the first low-temperature tempering, the tempering temperature is 230-300℃, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature;

[0024] T5. Second low-temperature tempering: The blank product that has been tempered for the first time is subjected to a second low-temperature tempering, wherein the tempering temperature is 230-350°C, the tempering insulation time is 4 hours, and then cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0025] Further optimization: In step 22, after the production of the blank product is completed, the processing standard of the blank product is as follows: the diameter size tolerance is -0.085 to -0.075 mm; the surface finish is Ra0.2, the outer diameter roundness is 0.003; the cylindricity is 0.003, and the concentricity is φ0.005.

[0026] Further optimization: In step T1, the heating furnace is a pit-type furnace, and the furnace loading method is: hoisting with a hanging plate; the number of furnaces loaded is 4-5 per furnace.

[0027] Further optimization: In step T1, when keeping warm, the keeping temperature fluctuation is: ±5°C.

[0028] Further optimization: In step T2, the initial temperature of the quenching medium is 20-50°C, and the outlet water temperature of the quenching medium is 200-240°C.

[0029] Further optimization: In step T2, the quenching medium is brine, and the concentration of the brine is 3%.

[0030] The present invention adopts the above technical scheme, which is ingenious in conception and reasonable in structure, and solves the problem that the internal and external strength and toughness of large-sized hydraulic breaker pistons made of high-carbon steel are difficult to match; more importantly, by coordinating with corresponding processing and heat treatment processes, the strength and toughness of the entire cross-section of the large-sized hydraulic breaker piston can be balanced, effectively alleviating the phenomenon of sudden changes in hardness and toughness caused by size effect, and significantly improving the comprehensive strength and toughness of the large-sized hydraulic breaker piston.

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0033] Figure 2 is a cross-sectional view of a piston base body in an embodiment of the present invention;

[0034] Figure 3 It is a side view of the end surface of the circular countersunk hole on the piston base in the embodiment of the present invention;

[0035] Figure 4 Schematic diagram of tensile properties of comparative examples 1-3 of the present invention;

[0036] Figure 5 Schematic diagram of tensile properties of Examples 1-3 of the present invention;

[0037] Figure 6 This is a hardness comparison diagram between the comparative examples 1-3 and the embodiments 1-3 of the present invention;

[0038] Figure 7 This is a comparison diagram of the impact absorption work of the comparative examples 1-3 and the embodiments 1-3 of the present invention;

[0039] Figure 8 The residual stress diagram of comparative examples 1-3 of the present invention is

[0040] Fig. 9 Graph showing residual stress of Examples 1-3 of the present invention.

[0041] In the figure: 1-piston base; 2-circular counterbore; 3-first transition section; 4-second transition section; 5-third transition section. DETAILED DESCRIPTION

[0042] Example 1: Please refer to Figure 1-3 A large-sized hydraulic breaker piston comprises a piston base 1. The overall structure of the piston base 1 is cylindrical. A circular countersunk hole 2 is opened on one end surface of the piston base 1.

[0043] The piston base 1 is made of high carbon alloy steel, and the specific model of the high carbon alloy steel is 9CrV steel.

[0044] After the piston base body 1 made of high carbon alloy steel 9CrV is subjected to quenching and tempering treatment, the overall cross-section strength and toughness of the piston base body 1 are balanced without drastic performance changes.

[0045] The quenching and tempering treatment includes heating, quenching, nitrate bath and tempering processes.

[0046] The overall parameters of the manufactured hydraulic breaker piston are as follows: surface hardness: 55-65HRC; core hardness: 35-45HRC, and ultrasonic flaw detection ≤ level 2.

[0047] The overall diameter Φ1 of the piston base 1 is 180-260 mm, the overall height L1 of the piston base 1 is 410 mm, the overall diameter Φ2 of the circular countersunk hole 2 is 25-45 mm; the depth L2 of the circular countersunk hole 2 is 75-100 mm.

[0048] A plurality of transition sections are arranged on the outer surface of the piston base body 1 near an end surface having the circular counterbore 2 .

[0049] In this embodiment, the number of the transition sections is three, and the three transition sections are respectively a first transition section 3, a second transition section 4 and a third transition section 5, and the first transition section 3, the second transition section 4 and the third transition section 5 are sequentially connected as one body.

[0050] The outer surface shape of the first transition section 3 is a conical surface, the outer surface shape of the second transition section 4 is a cylindrical surface, and the outer surface shape of the third transition section 5 is a conical surface.

[0051] The outer surface diameter Φ4 of the second transition section 4 is 180 mm.

[0052] The piston base body 1 has an outer surface diameter Φ3 of 150 mm on one end surface of a circular counterbore 2 .

[0053] In this embodiment, a piston base 1 with an overall diameter Φ1 of 190 mm is taken as an example, wherein the overall height L1 of the piston base 1 is 410 mm; the overall diameter Φ2 of the circular countersunk hole 2 is 30 mm; the depth L2 of the circular countersunk hole 2 is 100 mm; the outer surface diameter Φ4 of the second transition section 4 is 180 mm; and the outer surface diameter Φ3 of the piston base 1 having one end face of the circular countersunk hole 2 is 150 mm.

[0054] The present invention adopts the above technical solution. The piston base 1 is made of 9CrV high carbon alloy steel, and after the piston is tempered, the overall cross-section strength and toughness of the piston base 1 are balanced, and the hardness and toughness mutation phenomenon caused by the size effect is effectively alleviated, which significantly improves the comprehensive strength and toughness of the large-size hydraulic breaker piston, and the piston has excellent fatigue strength and corrosion resistance.

[0055] This embodiment 1 also discloses a method for manufacturing a large-sized hydraulic breaker piston, the manufacturing method comprising the machining steps:

[0056] S1. Cutting: Select high carbon alloy steel 9CrV that is suitable for manufacturing large-size hydraulic breaker pistons for production. The raw materials of 9CrV steel must be inspected before entering the factory.

[0057] In step S1, the inspection of the 9CrV steel raw material is carried out according to the following steps:

[0058] 1. Supply status: The preparation process of 9CrV steel raw materials includes: die casting, forging, and spheroidizing annealing.

[0059] 2. Chemical composition: Sampling and testing are carried out at the end face of the 9CrV steel raw material and 0.5R (R represents the radius of the 9CrV steel raw material) from the surface. The sampling quantity is 1 piece / heat;

[0060] The percentage content of each element in 9CrV steel is shown in the following table:

[0061]

[0062] 3. Macrostructure: Sampling location: the end of 9CrV steel raw material; Sampling quantity: 1 piece / heat;

[0063] Requirements: Referring to GB / T18254-2016, there should be no harmful defects such as residual shrinkage cavities, cracks, subcutaneous bubbles, overburning, white spots, etc. on the transverse acid immersion specimen.

[0064]

[0065] 4. Supply hardness: Spheroidizing annealing hardness is not more than HBW179-229.

[0066] 5. Decarburization layer: Sampling location: the end of 9CrV steel raw material; Sampling quantity: 1 piece / heat; Requirements: The total decarburization layer depth on each side shall not exceed 1% of the nominal diameter.

[0067] 6. Non-metallic inclusions:

[0068]

[0069] 7. Microstructure

[0070]

[0071] 8. Ultrasonic nondestructive testing: Sampling quantity: one by one; Requirements: Refer to GB / T 4612, the diameter of a single discontinuous flat-bottom hole ≤ Grade 2.0.

[0072] S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston. First, a lathe is used to perform rough turning to obtain a rough-turned blank, and then the rough-turned blank is fine-turned by a lathe to obtain a fine-turned blank. The fine-turned blank is milled by a milling machine to finally obtain a blank product.

[0073] After the production of the blank product is completed, the processing standards of the blank product are as follows: the diameter size tolerance is -0.085 to -0.075 mm; the surface finish is Ra0.2, the outer diameter roundness is 0.003; the cylindricity is 0.003, and the concentricity is φ0.005.

[0074] The manufacturing method also includes a tempering step:

[0075] T1. Heating: Place the rough product into a heating furnace and heat it to 850°C at a heating rate of 5-10°C / min. Maintain a carbon potential protective atmosphere of 0.8-1.1% in the heating furnace and then keep it warm for 5 hours.

[0076] In step T1, the heating furnace is a pit-type furnace, and the furnace loading method is: hoisting with a hanging plate; the number of furnaces loaded is 4 per furnace.

[0077] In step T1, when heat preservation is performed, the heat preservation temperature fluctuates within ±5°C.

[0078] T2. Quenching: The heated and heat-insulated blank product is placed in the air for precooling. The precooling time is 1 minute. After precooling, it is placed in the quenching medium for quenching. The initial temperature of the quenching medium is 20-50°C, the quenching time is 2.5 minutes, and the outlet water temperature of the quenching medium is 200-240°C. After quenching, the temperature of the blank product is 200°C.

[0079] In step T2, the quenching medium is brine, and the concentration of the brine is 3%.

[0080] In step T2, the purpose of precooling is to relieve the stress of the piston and avoid stress concentration.

[0081] In step T2, when salt water is used as the quenching medium for quenching, it is easy to obtain a higher hardness and a smooth surface, and it is not easy to produce soft spots that cannot be hardened. In addition, pre-cooling the blank product before quenching can relieve the stress of the piston and avoid stress concentration, thereby preventing serious deformation of the workpiece and causing cracking problems.

[0082] And through this quenching process, the hardness, strength and wear resistance of the piston can be improved, and the organization can be prepared for subsequent heat treatment.

[0083] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0084] In step T3, the nitrate bath treatment can enable the piston to obtain an excellent quenching structure, reduce quenching deformation, and reduce the tendency of piston cracking, thereby increasing the service life of the piston.

[0085] T4. First low-temperature tempering: The blank product after the nitrate bath treatment is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 230°C, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature.

[0086] T5. Second low-temperature tempering: The blank product after the first low-temperature tempering is loaded into a low-temperature tempering furnace for the second low-temperature tempering, wherein the tempering temperature is 230°C and the tempering holding time is 4 hours. After the second tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0087] This design uses two low-temperature temperings to fully eliminate the residual stress generated during piston quenching and prevent deformation and cracking; it can also adjust the hardness, strength, plasticity and toughness of the piston to meet performance requirements; and it can also stabilize the structure and size to ensure accuracy.

[0088] Embodiment 2: In this embodiment, the overall structure of the large-size hydraulic breaker piston is the same as that in the above-mentioned embodiment 1.

[0089] This embodiment 2 also discloses a method for manufacturing a large-sized hydraulic breaker piston, which includes machining steps:

[0090] S1. Cutting: Select high carbon alloy steel 9CrV that is suitable for manufacturing large-size hydraulic breaker pistons for production. The raw materials of 9CrV steel must be inspected before entering the factory.

[0091] The inspection steps of the raw materials are the same as those in the above-mentioned embodiment 1.

[0092] S2. Machining is performed according to the overall size of the large-sized hydraulic breaker piston. First, a lathe is used to perform rough turning to obtain a rough-turned blank, and then the rough-turned blank is fine-turned by a lathe to obtain a fine-turned blank. The fine-turned blank is milled by a milling machine to finally obtain a blank product. The processing standards of the blank product are as follows: the diameter size tolerance is -0.085 to -0.075 mm; the surface finish is Ra0.2, the outer diameter roundness is 0.003; the cylindricity is 0.003, and the concentricity is φ0.005.

[0093] The manufacturing method also includes a tempering step:

[0094] T1. Heating: Load the rough product into the pit furnace, where the loading method is: hoisting with a hanging plate; the number of furnaces loaded is 4 / furnace, and the temperature is raised to 820℃ at a heating rate of 7℃ / min. The carbon potential protective atmosphere in the heating furnace is maintained at 1%, and then kept warm for 5 hours. During the insulation, the insulation temperature fluctuation is: ±5℃.

[0095] T2. Quenching: The heated and heat-insulated blank product is placed in the air for precooling. The precooling time is 1 minute. After precooling, it is placed in 3% brine for quenching. The initial temperature of the brine is 35°C. The quenching time is 4 minutes. The outlet water temperature of the quenching medium is 220°C. After quenching, the temperature of the blank product is 245°C.

[0096] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0097] T4. First low-temperature tempering: The blank product after the nitrate bath treatment is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 230°C, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature.

[0098] T5. Second low-temperature tempering: The blank product after the first low-temperature tempering is loaded into a low-temperature tempering furnace for the second low-temperature tempering, wherein the tempering temperature is 350°C and the tempering holding time is 4 hours. After the second tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0099] This design uses two low-temperature temperings to fully eliminate the residual stress generated during piston quenching and prevent deformation and cracking; it can also adjust the hardness, strength, plasticity and toughness of the piston to meet performance requirements; it can also stabilize the structure and size to ensure accuracy, and the last overall tempering at 350°C allows the entire piston to be tempered in the bainite medium-temperature tempering zone.

[0100] Embodiment 3: In this embodiment, the overall structure of the large-size hydraulic breaker piston is the same as that in the above-mentioned embodiment 1.

[0101] This embodiment 3 also discloses a method for manufacturing a large-sized hydraulic breaker piston, which includes machining steps:

[0102] S1. Cutting: Select high carbon alloy steel 9CrV that is suitable for manufacturing large-size hydraulic breaker pistons for production. The raw materials of 9CrV steel must be inspected before entering the factory.

[0103] The inspection steps of the raw materials are the same as those in the above-mentioned embodiment 1.

[0104] S2. Machining is performed according to the overall size of the large-sized hydraulic breaker piston. First, a lathe is used to perform rough turning to obtain a rough-turned blank, and then the rough-turned blank is fine-turned by a lathe to obtain a fine-turned blank. The fine-turned blank is milled by a milling machine to finally obtain a blank product. The processing standards of the blank product are as follows: the diameter size tolerance is -0.085 to -0.075 mm; the surface finish is Ra0.2, the outer diameter roundness is 0.003; the cylindricity is 0.003, and the concentricity is φ0.005.

[0105] The manufacturing method also includes a tempering step:

[0106] T1. Heating: Load the rough product into the pit furnace, where the loading method is: lifting by a hanging plate; the number of furnaces loaded is 4 / furnace, and the temperature is raised to 850℃ at a heating rate of 10℃ / min. The carbon potential protective atmosphere in the heating furnace is maintained at 1.1%, and then kept warm for 5 hours. During the insulation, the insulation temperature fluctuation is: ±5℃.

[0107] T2. Quenching: The heated and heat-insulated blank product is placed in the air for pre-cooling for 1 minute. After pre-cooling, it is placed in 3% brine for quenching. The initial temperature of the brine is 50°C, the quenching time is 4 minutes, and the outlet water temperature of the quenching medium is 240°C. After quenching, the temperature of the blank product is 290°C.

[0108] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0109] T4. First low-temperature tempering: The blank product treated with nitrate bath is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 300°C, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature.

[0110] T5. Second low-temperature tempering: The blank product after the first low-temperature tempering is loaded into a low-temperature tempering furnace for the second low-temperature tempering, wherein the tempering temperature is 350°C and the tempering holding time is 4 hours. After the second tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0111] This design uses two low-temperature temperings to fully eliminate the residual stress generated during piston quenching and prevent deformation and cracking; it can also adjust the hardness, strength, plasticity and toughness of the piston to meet performance requirements; it can also stabilize the structure and size to ensure accuracy, and the last overall tempering at 350°C allows the entire piston to be tempered in the bainite medium-temperature tempering zone.

[0112] Comparative Example 1:

[0113] A method for manufacturing a large-size hydraulic breaker piston, the manufacturing method comprising the steps of machining:

[0114] S1. Cutting materials: Select high carbon alloy steel 9CrV for production. The raw materials of 9CrV steel need to be inspected before entering the factory. The inspection steps are the same as those in the above-mentioned embodiment 1.

[0115] S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston, and the rough product is finally obtained through rough turning, fine turning and milling.

[0116] The manufacturing method also includes a tempering step:

[0117] T1. Heating: Load the rough product into a pit furnace with 4 furnaces per furnace. Heat it to 850°C at a rate of 10°C / min. Maintain the carbon potential protective atmosphere at 0.8% in the heating furnace and keep it warm for 5 hours.

[0118] T2. Quenching: pre-cool the heated and heat-insulated blank product in the air for 1 minute. After pre-cooling, put it into 3% salt water for quenching. The initial temperature of the salt water is 20°C, the quenching time is 2.5 minutes, and the outlet water temperature of the quenching medium is 200°C.

[0119] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0120] T4. First low-temperature tempering: The rough product after the nitrate bath treatment is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 230°C and the tempering holding time is 4 hours. After the first tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0121] Comparative Example 2:

[0122] A method for manufacturing a large-size hydraulic breaker piston, the manufacturing method comprising the steps of machining:

[0123] S1. Cutting materials: Select high carbon alloy steel 9CrV for production. The raw materials of 9CrV steel need to be inspected before entering the factory. The inspection steps are the same as those in the above-mentioned embodiment 1.

[0124] S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston, and the rough product is finally obtained through rough turning, fine turning and milling.

[0125] The manufacturing method also includes a tempering step:

[0126] T1. Heating: Load the rough product into a pit furnace with 4 furnaces per furnace. Heat the temperature to 800°C at a rate of 7°C / min. Maintain the carbon potential protective atmosphere in the heating furnace at 1%, and then keep warm for 5 hours.

[0127] T2. Quenching: pre-cool the heated and heat-insulated blank product in the air for 1 minute, and then put it into 3% salt water for quenching. The initial temperature of the salt water is 35°C, the quenching time is 4 minutes, and the outlet water temperature of the quenching medium is 220°C.

[0128] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0129] T4. First low-temperature tempering: The blank product treated with nitrate bath is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 400°C, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature.

[0130] T5. Second low-temperature tempering: The blank product that has completed the first low-temperature tempering is loaded into a low-temperature tempering furnace for the second low-temperature tempering, wherein the tempering temperature is 400°C and the tempering holding time is 4 hours. After the second tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0131] Comparative Example 3:

[0132] A method for manufacturing a large-size hydraulic breaker piston, the manufacturing method comprising the steps of machining:

[0133] S1. Cutting materials: Select high carbon alloy steel 9CrV for production. The raw materials of 9CrV steel need to be inspected before entering the factory. The inspection steps are the same as those in the above-mentioned embodiment 1.

[0134] S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston, and the rough product is finally obtained through rough turning, fine turning and milling.

[0135] The manufacturing method also includes a tempering step:

[0136] T1. Heating: Load the rough product into a pit furnace with 4 furnaces per furnace. Heat it to 800°C at a heating rate of 10°C / min. Maintain the carbon potential protective atmosphere at 1.1% in the heating furnace and keep it warm for 5 hours.

[0137] T2. Quenching: pre-cool the heated and heat-insulated blank product in the air for 1 minute. After pre-cooling, put it into 3% salt water for quenching. The initial temperature of the salt water is 50°C, the quenching time is 4 minutes, and the outlet water temperature of the quenching medium is 240°C.

[0138] T3. Nitrate bath: put the quenched blank product into a nitrate furnace for nitrate bath, where the nitrate bath temperature is 230°C and the nitrate bath insulation time is 4 hours.

[0139] T4. First low-temperature tempering: The blank product after the nitrate bath treatment is placed in a low-temperature tempering furnace for the first low-temperature tempering, wherein the tempering temperature is 230°C, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature.

[0140] T5. Second low-temperature tempering: The blank product that has completed the first low-temperature tempering is loaded into a low-temperature tempering furnace for the second low-temperature tempering, wherein the tempering temperature is 400°C and the tempering holding time is 4 hours. After the second tempering treatment is completed, it is cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

[0141] The large-size hydraulic breaker pistons prepared in the above Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests:

[0142] 1. The tensile properties of the large-size hydraulic breaker pistons prepared in Examples 1-3 and Comparative Examples 1-3 at different radial positions of the cross section were tested. The test structure is as follows: Figure 4-5 shown.

[0143] 2. The hardness of the large-size hydraulic breaker piston prepared in Examples 1-3 and Comparative Examples 1-3 at different radial positions of the cross section was tested. The test structure is as follows: Figure 6 shown.

[0144] 3. The impact absorption work at different radial positions of the cross section of the large-size hydraulic breaker piston prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The testing structure is as follows: Figure 7 shown.

[0145] 4. The residual stress at different radial positions of the cross section of the large-size hydraulic breaker piston prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The test structure is as follows: Figure 8-9 shown.

[0146] The above tests show that the piston produced by the process of the present invention has better tensile properties, hardness and impact absorption energy than the piston produced by the prior art, thereby improving the overall structural strength of the piston, and improving the service life and use effect.

[0147] For those skilled in the art, according to the teachings of the present invention, without departing from the principles and spirit of the present invention, changes, modifications, substitutions and variations made to the implementation methods are still within the protection scope of the present invention.

Claims

1. A method for manufacturing a large-size hydraulic breaker piston, characterized in that: The piston comprises a piston base (1) made of high-carbon alloy steel 9CrV, the piston base (1) being made through quenching and tempering treatment; a circular countersunk hole (2) is formed on one end surface of the piston base (1); The surface hardness of the piston is: 57-63HRC; ultrasonic flaw detection ≤ level 2; A first transition section (3), a second transition section (4) and a third transition section (5) which are connected in sequence and integrated are arranged on the outer surface of the piston base body (1) at a position close to an end surface having a circular counterbore (2); The manufacturing method comprises the machining steps: S1. Cutting: Select high carbon alloy steel 9CrV that is suitable for manufacturing large-size hydraulic breaker pistons for production. The raw materials of 9CrV steel must be inspected before entering the factory; S2. Machining is performed according to the overall size of the large-size hydraulic breaker piston to finally obtain a rough product; The manufacturing method also includes a tempering step: T1. Heating: Place the rough product into a heating furnace and heat it to 820-850°C at a heating rate of 5-10°C / min. Maintain a carbon potential protective atmosphere of 0.8-1.1% in the heating furnace and then keep it warm for 5 hours; T2, quenching: put the heated and heat-insulated blank product in the air for precooling for 1 minute, and then put it into the quenching medium for quenching after precooling. The quenching time is 2.5-4 minutes. After quenching, the temperature of the blank product is 200-290℃; T3, nitrate bath: put the quenched blank product into nitrate bath, where the nitrate bath temperature is 230℃ and the nitrate bath insulation time is 4 hours; T4, first low-temperature tempering: The blank product treated with nitrate bath is subjected to the first low-temperature tempering, the tempering temperature is 230-300℃, the tempering holding time is 4 hours, and the first tempering treatment is completed and cooled to room temperature; T5. Second low-temperature tempering: The blank product that has been tempered for the first time is subjected to a second low-temperature tempering, wherein the tempering temperature is 230-350°C, the tempering insulation time is 4 hours, and then cooled to room temperature to finally obtain a large-sized hydraulic breaker piston.

2. The method for manufacturing a large-size hydraulic breaker piston according to claim 1, characterized in that: In step 22, after the production of the blank product is completed, the processing standard of the blank product is as follows: the diameter size tolerance is -0.085 to -0.075 mm; the surface finish is Ra0.2, the outer diameter roundness is 0.003; the cylindricity is 0.003, and the concentricity is φ0.

005.

3. The method for manufacturing a large-size hydraulic breaker piston according to claim 2, characterized in that: In step T1, the heating furnace is a pit-type furnace, and the furnace loading method is: hoisting with a hanging plate; the number of furnaces loaded is 4-6 per furnace.

4. The method for manufacturing a large-size hydraulic breaker piston according to claim 3, characterized in that: In step T1, when keeping warm, the keeping temperature fluctuates by ±5°C.

5. The method for manufacturing a large-size hydraulic breaker piston according to claim 4, characterized in that: In step T2, the initial temperature of the quenching medium is 20-50°C, and the outlet water temperature of the quenching medium is 200-240°C.

6. The method for manufacturing a large-size hydraulic breaker piston according to claim 5, characterized in that: In step T2, the quenching medium is brine, and the concentration of the brine is 3%.

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