Preparation method of high-wear-resistance cutting pick

Abstract

The invention belongs to the technical field of cutting pick preparation processes, and particularly relates to a preparation method of a high-wear-resistance cutting pick, which is characterized in that steel for a cutting pick body comprises the following chemical components in percentage by mass: 0.55 to 0.75 percent of C, 0.9 to 1.2 percent of Cr, 0.15 to 0.30 percent of Mo, 0.5 to 1.0 percent of V, 0.17 to 0.37 percent of Si, 0.5 to 0.8 percent of Mn, trace elements and the balance of Fe; the trace elements comprise 0.05 to 0.1 percent of Ni, 0.002 to 0.005 percent of B, 0.005 to 0.01 percent of Nb, 0.005 to 0.01 percent of Ti, less than 0.035 percent of S and less than 0.035 percent of P; the preparation method comprises the following steps: 1) preparing the cutting pick body; (2) preparing the cutting pick; and 3) carrying out isothermal quenching heat treatment on the cutting pick. The method has the beneficial effects that steel is optimized in microstructure and performance by optimizing steel components for the cutting pick body and parameters such as temperature, time and cooling rate of each heat treatment link, the wear resistance of the cutting pick is excellent, the urgent requirement for high performance of the cutting pick in modern industrial production is met, and the service life of the cutting pick is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of pick preparation technology, and in particular relates to a method for preparing a pick with high wear resistance. Background Art

[0002] In many fields such as mechanical processing, mining, and engineering machinery, the performance requirements for picks are increasing. As a key component, the pick frequently comes into contact with hard rocks and minerals under harsh working conditions, and is subjected to extremely high stress, wear, and impact. Picks are key components for directly cutting coal and rock in the coal industry. Picks consist of carbide tooth tips embedded in the alloy head mounting holes of the alloy steel pick body head and fixed by brazing. The main forms of pick failure are carbide tooth shedding, tooth tip crushing, and tooth body bending or breaking after the pick body head wears out. Among them, failures caused by tooth tip shedding due to wear of the pick body head account for about 85% of all failures. The pick body is not wear-resistant enough, and the carbide tooth tip falls off prematurely, causing the entire pick to be damaged and fail prematurely. With the increase in the power of coal mining machines, in order to extend the service life of the pick, the pick body is required to have higher wear resistance, strength, and impact resistance.

[0003] Chinese invention patent application number 201310325713.0 discloses a method for preparing a laser cladding-strengthened pick holder. The method involves pretreating the semicircumferential surface of a conventional pick holder substrate to prepare an alloy powder having the following chemical composition by weight: C 0.15-0.85%, Cr 7.5-25%, Ni 2.5-32%, Mo 5-15%, W 2.7-4.7%, Si 2.6-4.26%, Nb 1.81-3.21%, with the remainder being Fe. The pick holder is then mounted on a laser processing machine and scanned with a high-power semiconductor laser beam. This allows the alloy powder, delivered to the pick holder by pneumatic, gravity, powder spreading, or rubber powder, to undergo a rapid metallurgical reaction with the metal on the substrate surface, resulting in a uniform, impact-resistant, and wear-resistant alloy layer 0.6-1.8 mm thick. This method, which lacks heat treatment, exhibits poor strength and wear resistance.

[0004] Chinese invention patent application number 89101285.0 discloses a pick with a high-hardness, wear-resistant coating and its preparation process. A specific thermal spraying (welding) process is used to spray-weld a layer of high-hardness, wear-resistant alloy onto the head of the shearer pick. This alloy layer has a good metallurgical bond with the pick body and is highly hard, wear-resistant, and non-brittle. The product of the present invention has excellent mechanical properties, a lifespan approximately 0.5-1 times longer than that of conventional inlaid carbide picks, and a simple preparation process. The solution mentions austempering heat treatment, but does not disclose the specific operating steps and related parameters. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing highly wear-resistant picks, overcome the shortcomings of the existing technology, optimize the steel composition of the pick body and the parameters such as temperature, time and cooling rate of each heat treatment link, optimize the steel in microstructure and performance, improve the strength and wear resistance of the picks, meet the urgent demand of modern industry for high performance of picks, improve the strength and wear resistance of the high-strength steel, and extend the service life of the picks.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for preparing a high-wear-resistant pick, wherein the chemical composition of the steel used for the pick body is as follows by mass percentage: C 0.55-0.75%, Cr 0.9-1.2%, Mo 0.15-0.30%, V 0.5-1.0%, Si 0.17-0.37%, Mn 0.5-0.8%, trace elements, and the balance is Fe; the trace elements are Ni 0.05-0.1%, B 0.002-0.005%, Nb 0.005-0.01% and T i0.005-0.01%; S<0.035%, P<0.035%; A method for preparing a high-wear-resistant pick, comprising the following steps: 1) preparing a pick body, alloying the pick body with steel and forging it into a bar, further forging the bar into a pick body rough blank by high-temperature or medium-temperature die forging, spheroidizing annealing or normalizing the pick body rough blank, machining the treated pick body rough blank into a pick body fine blank, and machining a mounting hole for the alloy tooth tip on the head;

[0008] 2) Preparation of the pick: Surface cladding treatment is performed on the surface of the pick body blank. The cladding treatment range is the outside of the alloy head mounting hole. The plasma or laser cladding method is used. The cladding layer thickness is 2-3mm, and the width of each cladding layer is ≥25mm. Medium frequency induction brazing is used to connect the alloy tooth tip and the pick body blank to form a pick.

[0009] 3) Perform austempering heat treatment on the pick, control the phase change rate and temperature control cooling after austempering. The pick needs to be cooled to below 40°C before tempering. The tempering is carried out in a gas-shielded furnace or a vacuum furnace. The time interval between quenching and tempering is within 4 hours; air cooling is used during tempering in a gas-shielded furnace.

[0010] Furthermore, in step 1), the alloy smelting is performed by vacuum induction, medium frequency induction or electroslag remelting, and the smelted steel ingot is subjected to homogenization diffusion treatment at 1200-1250° C. for 10-15 hours.

[0011] Furthermore, the spheroidizing annealing in the step 1) is performed in a gas shielded annealing furnace or a vacuum furnace, and the preheating temperature of the spheroidizing annealing is 700-750°C, the preheating time is 2-3h, and then the spheroidizing annealing is performed at 790-860°C, the holding time is 4-6h, and then the spheroidizing annealing is performed at 700-730°C, the holding time is 6-10h, and then the spheroidizing annealing is performed at a rate of 20°C / h to 600°C, and then the spheroidizing annealing is performed at 500-550°C, and then the spheroidizing annealing is performed and air-cooled.

[0012] Furthermore, the normalizing treatment is performed at a heating temperature of 860° C., maintained at that temperature for 2-3 hours, and then cooled in air.

[0013] Furthermore, the surface cladding in step 2) is an iron-based wear-resistant cladding layer or a nickel-based wear-resistant cladding layer.

[0014] Furthermore, the medium frequency induction brazing process in step 2) is to heat the pick body to 880-910°C, use H62 copper or BCuZnMn as the brazing material, and after brazing, keep it in a salt bath at 220-260°C for 0.2-2h, and then slowly cool it to room temperature.

[0015] Furthermore, the austempering heat treatment in step 3) is salt bath austempering, the pick is placed in a heating furnace, first heated to 660-700°C at a rate of 8-10°C / min, kept warm for 30-60min, then heated to 800-860°C at a rate of 5-8°C / min, kept warm for 30-120min, and after the insulation is completed, it is taken out of the furnace for quenching and quenched into a salt bath with a furnace temperature of 200-250°C for 2-4h.

[0016] Furthermore, the time from the time the pick is taken out of the heating furnace to the time the pick is completely immersed in the salt bath during the quenching process is less than 20 seconds; the salt bath furnace has a stirring function, and the salt bath flows from the bottom to the top of the basket.

[0017] Furthermore, in the step 3), the cooling rate of the pick is controlled by controlling the phase transformation rate and the temperature-controlled cooling process after the isothermal quenching, so that the pick is cooled from the quenching temperature to 40° C. within 30-60 minutes.

[0018] Furthermore, the tempering parameter requirements in step 3) are: the vacuum degree in the furnace is 5×10 -1 -5×10 -2 Pa, heat to 350-380℃ at a rate of 6-10℃ / min, keep warm for 2-5h, cool to below 40℃ with air cooling pressure of 0.6bar-1.5bar.

[0019] The pick body steel of the present invention is added with strengthening elements such as V, B, Ti, and Nb, which is of great significance for achieving performance optimization, among which boron (B): Boron mainly plays the role of refining grains and improving hardenability in steel. An appropriate amount of boron can effectively refine austenite grains, make the grains finer and more uniform during the heat treatment process, thereby increasing the number of grain boundaries per unit area, hindering dislocation movement and crack propagation, and improving the strength and toughness of steel. At the same time, boron is also an element that promotes the formation of bainite, can reduce the incubation period of lower bainite formation, and increase the amount of high-strength, high-toughness, and wear-resistant bainite formed by isothermal quenching heat treatment. Good hardenability can ensure that the pick obtains a uniform martensitic structure during the quenching process, enhances its hardness and wear resistance, and enables it to maintain a sharp cutting edge more durably under complex working conditions.

[0020] Vanadium (V): Vanadium is a strong carbide-forming element, and its carbides have high hardness and good thermal stability. When vanadium is added to steel, it combines with carbon to form fine VC-type carbides. These carbides are dispersed in the matrix, playing a dispersion strengthening role, hindering the growth of austenite grains in the steel, improving the thermal stability of the steel, effectively hindering dislocation slip, and significantly increasing the strength and hardness of the steel. In addition, during the operation of the pick, the vanadium carbides can resist the cutting and plowing effects of abrasives, enhance the wear resistance of the pick surface, extend the service life of the pick, reduce the frequency of replacement, and improve work efficiency.

[0021] Titanium (Ti): Titanium exists primarily in steel in the form of titanium carbide (TiC), which is extremely hard and can significantly improve the wear resistance of steel. The addition of TiC refines the steel's grain size. During heat treatment, the presence of TiC prevents austenite grain growth, improving the steel's overall mechanical properties. Furthermore, titanium can combine with harmful impurities such as oxygen and nitrogen to form stable compounds, purifying the molten steel, reducing internal defects, and increasing the purity of the steel, thereby indirectly improving the performance of the pick, making it more reliable and durable under complex working conditions.

[0022] Niobium (Nb): Niobium is a strong carbide-forming element, and its carbides possess high thermal stability. Adding niobium to steel refines the steel's grain size, increases its recrystallization temperature, and enhances its high-temperature strength and toughness. During pick manufacturing, after proper heat treatment, niobium carbides effectively pin dislocations, hindering their movement and aggregation, thereby increasing the steel's yield strength and tensile strength. Furthermore, the fine grain structure and dispersed carbides enhance the steel's wear resistance, enabling the pick to maintain excellent performance under high stress and wear, adapting to a variety of complex operating conditions.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) By optimizing the steel composition of the pick body and parameters such as temperature, time and cooling rate of each heat treatment step, the steel is optimized in terms of microstructure and performance. The pick has excellent strength and wear resistance, meeting the urgent demand for high performance of picks in modern industrial production and extending the service life of the picks.

[0025] 2) The austempering heat treatment of the present invention is salt bath austempering, which helps to ensure that the parts after heating need less cooling and controls the precipitation of carbides before quenching. The salt bath in the salt bath furnace flows from the bottom to the top of the basket, forming an effective flow, ensuring that the parts can be evenly cooled, while ensuring the uniformity of the salt furnace temperature;

[0026] 3) Controlling the phase transformation rate and temperature-controlled cooling after austempering. By controlling the cooling rate of the steel, the speed at which austenite in the steel forms martensite is controlled, and ultimately the residual stress in the parts is effectively controlled, thereby improving the wear resistance of the high-strength steel without reducing the strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the processing of the pick body in an embodiment of the present invention.

[0028] Figure 2 Metallographic diagram of the martensitic structure of the pick obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the specific embodiments required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some implementation methods of the present invention. For ordinary technicians in this field, other specific embodiments can be obtained based on these specific embodiments without paying any creative work.

[0031] The components of the embodiments of the present invention generally described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific embodiments is not intended to limit the scope of the claimed invention, but is merely representative of selected embodiments of the present invention.

[0032] An embodiment of a method for preparing a high wear-resistant pick according to the present invention,

[0033] Example 1

[0034] A method for preparing a high-wear-resistant pick. The chemical composition of the steel used for the pick body is, by mass percentage, C0.55wt%, Cr1.0wt%, Mo0.2wt%, V0.75wt%, Si0.25wt%, Mn0.75wt%, trace elements, and Fe as the balance; the trace elements are Ni0.1wt%, B0.002wt%, Nb0.005wt%, and Ti0.005wt%.

[0035] Embodiment 1 of the present invention provides a method for preparing a high-wear-resistant pick, which specifically comprises the following steps:

[0036] 1) Preparation of the pick body: alloying the pick body with steel and forging it into The bar is further forged into a rough cutter body blank by high-temperature die forging or medium-temperature die forging. The rough cutter body blank is then spheroidized annealed and machined to obtain a fine cutter body blank. The alloy head mounting hole is machined. The alloy is smelted using a gas shielded electroslag remelting process. The smelted steel ingot undergoes a homogenization diffusion treatment at 1200°C for 10 hours. A gas shielded annealing furnace is used for spheroidizing annealing. The preheating temperature for spheroidizing annealing is 700°C for 3 hours, followed by heating to 810°C and holding for 6 hours. The product is then cooled to 720°C and held for 8 hours. The product is then cooled at a rate of 20°C / h to 600°C. The product is then cooled to 500°C and removed from the furnace for air cooling.

[0037] 2) Preparation of the pick: The surface of the pick body blank is subjected to surface cladding treatment. The cladding treatment range is the outside of the alloy head mounting hole. The plasma cladding method is used, and the cladding layer is a 3mm thick iron-based wear-resistant cladding layer. The width of each cladding layer is ≥25mm; medium-frequency induction brazing is used to connect the alloy welding head to the pick body blank; brazing the alloy head is to heat the pick body to 910℃, use BCuZnMn as the brazing filler metal, and after brazing, keep it in a salt bath at 230℃ for 2h, and then slowly cool it to room temperature.

[0038] 3) The pick is subjected to austempering heat treatment. After austempering, the phase transformation rate and temperature-controlled cooling are controlled. The pick needs to be cooled to below 40°C before it can be tempered. Tempering is carried out in a gas-shielded furnace or a vacuum furnace. The time interval between quenching and tempering is 2 hours. The cooling method after gas-shielded furnace tempering is to cool in air. The austempering heat treatment is salt bath austempering. The pick is placed in a heating furnace and first heated to 700°C at a rate of 8°C / min and kept warm for 30 minutes. Then, the pick is heated to 860°C at a rate of 8°C / min and kept warm for 120 minutes. After the holding period, it is taken out of the furnace for quenching and quenched into a salt bath with a furnace temperature of 230°C for 2 hours. The time from the time the pick is taken out of the furnace after quenching and heating to the time the pick is completely immersed in the salt bath is 10 seconds, which is used to ensure that the heated parts can be cooled less and to control the precipitation of carbides before quenching. The salt bath furnace has a stirring function, and the direction of the salt bath flow is from the bottom to the top of the basket, forming an effective flow to ensure that the pick can be cooled evenly and at the same time ensure the uniformity of the salt furnace temperature. After isothermal quenching, the phase change rate in the pick is controlled by the temperature-controlled cooling process, so that it is cooled from the quenching temperature to 40°C within 30 minutes. By controlling the cooling rate, the speed at which austenite in the steel forms martensite is controlled, and the residual stress in the pick is controlled. Tempering of the pick, after quenching, the pick is cooled to below 40°C before tempering treatment can be carried out. The time interval for tempering after quenching is less than 4h. Tempering parameter requirements: the vacuum degree in the furnace is 1×10 -1 Pa, heat to 360℃ at a rate of 6℃ / min, keep warm for 2.5h, cool to below 40℃ with air cooling pressure of 0.8bar.

[0039] The pick obtained in Example 1 had a Vickers hardness of 630 HV, as measured using a Vickers hardness tester. Using a reciprocating friction and wear tester under a pressure of 1000 N, a displacement speed of 10 mm / min, and a sliding distance of 6 mm, the friction and wear weight loss was 2.8 mg. The tensile strength was 1645 MPa, the yield strength was 1460 MPa, and the elongation was 12.5%.

[0040] Example 2

[0041] A method for preparing a high-wear-resistant pick. The chemical composition of the steel used for the pick body is, by mass percentage, C0.60wt%, Cr1.0wt%, Mo0.25wt%, V0.5wt%, Si0.25wt%, Mn0.75wt%, trace elements, and Fe as the balance; the trace elements are Ni0.1wt%, B0.002wt%, Nb0.005wt%, and Ti0.005wt%.

[0042] Embodiment 2 of the present invention provides a method for preparing a high-wear-resistant pick, which specifically comprises the following steps:

[0043] 1) Preparation of the pick body: alloying the pick body with steel and forging it into The bar is further forged into a rough cutter body blank by high-temperature die forging or medium-temperature die forging. The rough cutter body blank is spheroidized annealing treatment, and the treated rough cutter body blank is machined to obtain a fine cutter body blank, and the alloy head mounting hole is machined. The alloy is smelted using a gas shielded electroslag remelting process. The smelted steel ingot is homogenized and diffused at 1230℃ for 10 hours. The spheroidizing annealing is performed in a gas shielded annealing furnace. The preheating temperature for spheroidizing annealing is 700℃, the preheating time is 3 hours, then heated to 810℃, held for 6 hours, and then cooled to 720℃ with the furnace. The preheating time is 3 hours, then heated to 790℃, held for 6 hours, then cooled to 720℃ with the furnace, held for 8 hours, and then cooled to 600℃ at a rate of 20℃ / h. Then, the furnace is cooled to 500℃ and air-cooled.

[0044] 2) Preparation of the pick: The surface of the pick body blank is subjected to surface cladding treatment. The cladding treatment range is the outside of the alloy head mounting hole. The plasma cladding method is used, and the cladding layer is an iron-based wear-resistant cladding layer with a thickness of 2.5 mm. The width of each cladding layer is ≥25 mm; medium-frequency induction brazing is used to connect the alloy welding head to the pick body blank; brazing the alloy head is to heat the pick body to 900°C, use BCuZnMn as the brazing filler metal, and after brazing, keep it in a salt bath at 240°C for 2 hours, and then slowly cool it to room temperature.

[0045] 3) The pick is subjected to austempering heat treatment. After austempering, the phase transformation rate and temperature-controlled cooling are controlled. The pick needs to be cooled to below 40°C before it can be tempered. Tempering is carried out in a gas-shielded furnace or a vacuum furnace. The time interval between quenching and tempering is less than 4h. The pick after gas-shielded furnace tempering is cooled in air. The austempering heat treatment is salt bath austempering. The pick is placed in a heating furnace and first heated to 680°C at a rate of 9°C / min and kept warm for 30min. Then, the pick is heated to 840°C at a rate of 8°C / min and kept warm for 120min. After the holding period, it is taken out of the furnace for quenching and quenched into a salt bath with a furnace temperature of 230°C for 2h. The time from the time the pick is quenched out of the furnace to the time the pick is completely immersed in the salt bath is 10S, which is used to ensure that the heated parts can be cooled less and to control the precipitation of carbides before quenching. The salt bath furnace has a stirring function, and the flow direction of the salt bath flows from the bottom of the basket to the top, forming an effective flow to ensure that the pick can be cooled evenly and at the same time ensure the uniformity of the salt furnace temperature. After isothermal quenching, the cooling rate of the pick is controlled through the temperature-controlled cooling process to achieve the controlled phase transformation rate, so that it is cooled from the quenching temperature to 40°C within 50 minutes. By controlling the cooling rate, the speed at which austenite in the steel forms martensite is controlled, and the residual stress in the parts is controlled. Tempering of the pick, after quenching, it is cooled to below 40°C before tempering treatment can be carried out. The time interval for tempering after quenching is less than 4h. Tempering parameter requirements: the vacuum degree in the furnace is 5×10 -1 Pa, heat to 350℃ at a rate of 6℃ / min, keep warm for 3.5h, cool to below 40℃ with air cooling pressure of 0.6bar.

[0046] The pick obtained in Example 2 had a Vickers hardness of 500 HV, as measured using a Vickers hardness tester. Using a reciprocating friction and wear tester under a pressure of 1000 N, a displacement speed of 10 mm / min, and a sliding distance of 6 mm, the friction and wear weight loss was 4.3 mg. The tensile strength was 1320 MPa, the yield strength was 1210 MPa, and the elongation was 18.5%.

[0047] Example 3

[0048] A method for preparing a high-wear-resistant pick. The chemical composition of the steel used for the pick body is, by mass percentage, C0.75wt%, Cr1.2wt%, Mo0.30wt%, V1.0wt%, Si0.25wt%, Mn0.75wt%, trace elements, and Fe as the balance; the trace elements are Ni0.1wt%, B0.002wt%, Nb0.005wt%, and Ti0.005wt%.

[0049] Embodiment 3 of the present invention provides a method for preparing a high-wear-resistant pick, which specifically comprises the following steps:

[0050] 1) Preparation of the pick body: alloying the pick body with steel and forging it into The bar is further forged into a pick body blank through high-temperature or medium-temperature die forging. The pick body blank is normalized and machined into a pick body fine blank. The alloy head mounting hole is machined. The alloy is smelted using a gas-shielded electroslag remelting process. The smelted steel ingot is homogenized and diffused at 1250°C for 15 hours. The normalizing treatment is heated to 860°C for 2.5 hours and then cooled in air.

[0051] 2) Preparation of the pick: The surface of the pick body blank is subjected to surface cladding treatment. The cladding treatment range is the outside of the alloy head mounting hole. The laser cladding method is used, and the cladding layer is a nickel-based wear-resistant cladding layer with a thickness of 2 mm. The width of each cladding layer is ≥25 mm; medium-frequency induction brazing is used to connect the alloy welding head to the pick body blank; brazing the alloy head is to heat the pick body to 890°C, use H62 as the brazing filler metal, and after brazing, keep it in a salt bath at 260°C for 1.5 hours, and then slowly cool it to room temperature.

[0052] 3) The pick is subjected to austempering heat treatment. After austempering, the phase transformation rate and temperature-controlled cooling are controlled. The pick needs to be cooled to below 40°C before it can be tempered. Tempering is carried out in a gas-shielded furnace or a vacuum furnace, and the tempering time must be within 4 hours. Air cooling is used during gas-shielded furnace tempering. The austempering heat treatment is salt bath austempering. The pick is placed in a heating furnace, first heated to 660°C at a rate of 10°C / min, and kept warm for 60 minutes. Then, the pick is heated to 860°C at a rate of 6°C / min, and kept warm for 60 minutes. After the holding period, it is taken out of the furnace for quenching and quenched into a salt bath with a furnace temperature of 200°C for 4 hours. The quenching process takes 15 seconds from the time the pick is taken out of the furnace to the time the pick is completely immersed in the salt bath, to ensure that the heated parts can be cooled less and to control the precipitation of carbides before quenching. The salt bath furnace has a stirring function. The salt bath flows from the bottom of the basket to the top, forming an effective flow to ensure that the picks can be cooled evenly and the temperature of the salt bath is uniform. After austempering, the cooling rate of the picks is controlled by the temperature-controlled cooling process to control the phase transformation rate, so that it cools from the quenching temperature to 40°C within 40 minutes. By controlling the cooling rate, the speed at which austenite in the steel transforms into martensite is controlled, and the residual stress in the parts is controlled. Tempering parameter requirements: the vacuum degree in the furnace is 5×10 -2 Pa, heat to 380℃ at a rate of 10℃ / min, keep warm for 5h, cool to below 40℃ with air cooling pressure of 1.5bar.

[0053] The pick obtained in Example 3 had a Vickers hardness of 680 HV, as measured using a Vickers hardness tester. Using a reciprocating friction and wear tester under a pressure of 1000 N, a displacement speed of 10 mm / min, and a sliding distance of 6 mm, the friction and wear weight loss was 2.5 mg. The pick had a tensile strength of 1820 MPa, a yield strength of 1650 MPa, and an elongation of 11.3%.

[0054] Comparative Example

[0055] The pick body is made of 42CrMo steel, and its chemical composition is: C: 0.39wt%, Cr: 1.01wt%, Mo: 0.134wt%, Si: 0.285wt%, Mn: 0.65wt%, Ni: 0.006%, Cu: 0.016%, and Fe balance.

[0056] The preparation method of the comparative example pick of the present invention specifically comprises the following steps:

[0057] 1) Vacuum induction melting is used to smelt 42CrMo pick alloy, and gas shielded electroslag remelting is used after smelting. The smelted steel ingot is homogenized and diffused at 1200℃ for 10 hours, and then rolled or forged into a diameter of The pick body is die-forged from 42CrMo steel. The 42CrMo steel is normalized at 880°C for 2 hours, then air-cooled. The normalized pick body is machined to create the alloy head mounting hole.

[0058] 2) The processed pick body is subjected to surface cladding treatment. The outer side of the alloy head mounting hole is clad with a 3mm thick iron-based wear-resistant cladding layer using plasma cladding, with a cladding width of ≥25mm. The alloy head is brazed. The tooth body is heated to 890°C using medium-frequency electric heating, using BCuZnMn as the brazing filler metal. After brazing, the pick body is kept in a 240°C salt bath for 2 hours, and then slowly cooled to room temperature to obtain the semi-finished pick.

[0059] 3) Austempering heat treatment of the pick body. Austempering heat treatment is a salt bath austempering. 42CrMo steel is placed in a furnace with gas protection and isothermal salt bath quenching functions. The temperature is first raised to 700°C at a rate of 8°C / min and held at this temperature for 30 minutes to make the temperature in the steel uniform and dissolve some carbides. The sample is then heated to 860°C at a rate of 8°C / min and held for 120 minutes. After the holding period, it is removed from the furnace and quenched into a salt bath at a furnace temperature of 230°C for 2 hours. It is required to run from the heat treatment furnace to the salt bath furnace and be completely immersed in the salt bath for 15 seconds to ensure that the heated parts can cool less and control the precipitation of carbides before quenching. The salt bath furnace should have a stirring function. The salt bath flow direction is required to flow from the bottom to the top of the basket to form an effective flow to ensure uniform cooling of the parts and uniform temperature of the salt bath. After austempering, the phase transformation rate is controlled and the temperature is controlled. The components are removed from the salt bath and placed in a heat treatment furnace or insulated box with insulation function. The cooling rate of the steel is controlled so that the time required to cool from the quenching temperature to 40°C is 30 minutes. By controlling the cooling rate, the rate at which austenite in the steel transforms into martensite is controlled, thereby controlling the residual stress in the component. After quenching, the tooth body is cooled to below 40°C before tempering can be carried out. After quenching, the tempering interval is within 4 hours. Tempering is carried out in a gas-shielded furnace at a rate of 8°C / min to 360°C, held at this temperature for 2.5 hours, and then cooled in air to below 40°C.

[0060] The pick cutter obtained in the comparative example, after austempering and tempering, had a Vickers hardness of 539 HV using a Vickers hardness tester. Using a reciprocating friction and wear tester under a force of 1000 N, a displacement speed of 10 mm / min, and a sliding distance of 6 mm, the friction and wear weight loss was 3.6 mg. The tensile strength was 1550 MPa, the yield strength was 1230 MPa, and the elongation was 11.3%.

[0061] The mechanical property test results of the improved H13 and H13 steels under the austempering process of Examples 1-3 of the present invention and the comparative example are shown in Table 1.

[0062] Table 1

[0063]

[0064] By comparing Examples 1-3 with the comparative example, it can be found that the present invention has a larger range of variation in the hardness, wear resistance and elongation after fracture of the material. When the pick is used in a softer coal seam, the impact load on the pick is smaller and is mainly caused by wear. When the pick is used for hard rock mining, the comprehensive plastic and toughness properties of the pick can withstand higher impact loads.

[0065] It can be seen from the data in Table 1 that Examples 1 to 3 of the present invention can produce picks with high hardness, high strength and high wear resistance, which are suitable for increasing the service life of picks in coal seams and soft rock conditions.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high wear-resistant pick, characterized in that: The chemical composition of the steel for the pick body is as follows by mass percentage: C 0.55-0.75%, Cr 0.9-1.2%, Mo 0.15-0.30%, V 0.5-1.0%, Si 0.17-0.37%, Mn 0.5-0.8%, trace elements, and the balance is Fe; the trace elements are Ni 0.05-0.1%, B 0.002-0.005%, Nb 0.005-0.01% and Ti 0.005-0.01%; S<0.035%, P<0.035%; A method for preparing a high-wear-resistant pick comprises the following steps: 1) Preparation of the pick body: alloying the pick body with steel and forging it into a bar, further forging the bar into a pick body rough blank by high temperature die forging or medium temperature die forging, spheroidizing annealing or normalizing the pick body rough blank, machining the treated pick body rough blank to obtain a pick body fine blank, and machining the alloy tooth tip mounting hole on the head; 2) Preparation of the pick: Surface cladding treatment is performed on the surface of the pick body blank. The cladding treatment range is the outside of the alloy head mounting hole. The plasma or laser cladding method is used. The cladding layer thickness is 2-3mm, and the width of each cladding layer is ≥25mm. Medium frequency induction brazing is used to connect the alloy tooth tip and the pick body blank to form a pick. 3) Perform austempering heat treatment on the pick, control the phase change rate and temperature control cooling after austempering. The pick needs to be cooled to below 40°C before tempering. The tempering is carried out in a gas-shielded furnace or a vacuum furnace. The time interval between quenching and tempering is within 4 hours; air cooling is used during tempering in a gas-shielded furnace.

2. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: In the step 1), the alloy smelting is performed by vacuum induction, medium frequency induction or electroslag remelting. The smelted steel ingot is subjected to homogenization diffusion treatment at 1200-1250° C. for 10-15 hours.

3. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The spheroidizing annealing in the step 1) is performed in a gas shielded annealing furnace or a vacuum furnace. The preheating temperature of the spheroidizing annealing is 700-750°C for 2-3 hours, and then the spheroidizing annealing is heated to 790-860°C for 4-6 hours. The spheroidizing annealing is then cooled to 700-730°C for 6-10 hours. The spheroidizing annealing is then cooled to 600°C at a rate of 20°C / h, and then cooled to 500-550°C before being taken out of the furnace and air-cooled.

4. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The heating temperature of the normalizing treatment is 860° C., which is kept for 2-3 hours, and then cooled in air.

5. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The surface cladding in step 2) is an iron-based wear-resistant cladding layer or a nickel-based wear-resistant cladding layer.

6. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The medium frequency induction brazing process in step 2) is to heat the pick body to 880-910°C, use H62 copper or BCuZnMn as the brazing material, keep it in a salt bath at 220-260°C for 0.2-2h after brazing, and then slowly cool it to room temperature.

7. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The austempering heat treatment in step 3) is salt bath austempering, wherein the pick is placed in a heating furnace, first heated to 660-700°C at a rate of 8-10°C / min, and kept warm for 30-60 minutes, then heated to 800-860°C at a rate of 5-8°C / min, and kept warm for 30-120 minutes. After the heat preservation is completed, the pick is taken out of the furnace and quenched into a salt bath with a furnace temperature of 200-250°C for 2-4 hours.

8. The method for preparing a high wear-resistant pick according to claim 7, characterized in that: The time from the time the pick is taken out of the heating furnace to the time the pick is completely immersed in the salt bath during the quenching process is less than 20 seconds; the salt bath furnace has a stirring function, and the salt bath flows from the bottom to the top of the basket.

9. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The control of the phase transformation rate and the temperature-controlled cooling process after the isothermal quenching in step 3) controls the cooling rate of the pick so that it is cooled from the quenching temperature to 40° C. within 30-60 minutes.

10. The method for preparing a high wear-resistant pick according to claim 1, characterized in that: The tempering parameter requirements in step 3) are: the vacuum degree in the furnace is 5×10 -1 -5×10 -2 Pa, heat to 350-380℃ at a rate of 6-10℃ / min, keep warm for 2-5h, cool to below 40℃ with air cooling pressure of 0.6bar-1.5bar.

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