阅读说明：本技术 一种截齿齿体热处理工艺 (Cutting pick body heat treatment process ) 是由 何哲宇 陈明军 刘敏锋 朱彦兴 黄刚祥 于 2021-09-15 设计创作，主要内容包括：本发明一种截齿齿体热处理工艺,包括以下步骤：S1、将42CrMo不锈钢熔化成碳钢水后,添加1～3份Cr以及0.5～2份Mo；S2、将碳钢水浇铸成不锈钢棒材；S3、不锈钢棒材锻压后,机加工成型为截齿齿体；S4、淬将截齿齿体以5℃/min的升温速率加热至730～950℃后保温30～90min,再将截齿齿体置于乳化液或液氮中冷却至室温；S5、将淬火截齿齿体以5℃/min的升温速率加热至250～450℃后保温30～90min,再置于空气中冷却至室温。本发明以42CrMo为基础,通过调整C、Cr、Mo元素的相对含量和淬火、回火工艺,通过碳含量调整合金的硬度,控制硬质相的形貌和分布,提高齿体的高温强度。(The invention relates to a cutting pick body heat treatment process, which comprises the following steps: s1, melting 42CrMo stainless steel into molten carbon steel, and adding 1-3 parts of Cr and 0.5-2 parts of Mo; s2, casting carbon steel water into a stainless steel bar; s3, forging and pressing the stainless steel bar, and machining to form a cutting pick body; s4, heating the cutting tooth body to 730-950 ℃ at a heating rate of 5 ℃/min, then preserving heat for 30-90 min, and then placing the cutting tooth body in emulsion or liquid nitrogen to cool to room temperature; s5, heating the quenching pick body to 250-450 ℃ at a heating rate of 5 ℃/min, then preserving heat for 30-90 min, and then placing in air to cool to room temperature. The invention takes 42CrMo as a basis, adjusts the relative contents of C, Cr and Mo elements and quenching and tempering processes, adjusts the hardness of the alloy through the carbon content, controls the appearance and distribution of a hard phase and improves the high-temperature strength of a tooth body.)

1. A cutting pick body heat treatment process is characterized by comprising the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1-3 parts of Cr and 0.5-2 parts of Mo to carry out alloying;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000-1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the pick tooth body obtained in the step S3 to 730-950 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing the pick tooth body in emulsion or liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 250-450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing in air to cool to room temperature.

2. A cutting pick body heat treatment process according to claim 1, wherein: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1 part of Cr and 2 parts of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 750 ℃ at a heating rate of 5 ℃/min, then preserving heat for 60min, and then placing the cutting tooth body in an emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching cutting tooth body obtained in the step (S4) to 250 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing in air to cool to room temperature.

3. A cutting pick body heat treatment process according to claim 1, wherein: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 2 parts of Cr and 1 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 950 ℃ at a heating rate of 5 ℃/min, preserving heat for 90min, and then placing the cutting tooth body in liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 90min, and then placing in the air to cool to room temperature.

4. A cutting pick body heat treatment process according to claim 1, wherein: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 3 parts of Cr and 0.5 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1200 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 850 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing the cutting tooth body in emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 60min, and then placing in the air to cool to room temperature.

Technical Field

The invention belongs to the field of metal material design and heat treatment, and relates to a heat treatment process for a cutting pick body.

Background

Geological formations can be classified into low-hardness formations, hard rocks and high-hardness formations according to their hardness indexes. When construction operations such as tunnels, bridges, subways and the like are performed on high-hardness rock strata, the rock strata are usually perforated through a large rotary drilling rig, a shield machine and the like. These machines destroy the formation by rotating the working head. The core part of the working head is a cutting pick which is prepared by welding hard alloy on an alloy steel pick body. The engineering working condition carried out under the condition is extremely bad, the working temperature of the working head can reach 600-800 ℃, and the firmness coefficient of the rock can reach more than 12-15. Whereas the hardness of the main pick bodies currently on the market is generally below 40 HRC. The low-hardness pick body can cause the pick body to be easily abraded in the construction process, and the service life is short. In addition, the tooth body with poor use quality also easily causes the deformation of the working head, and reduces the service life of the engineering machinery. More seriously, the construction period is delayed, and even construction safety hidden dangers appear.

Hard rock formations are widespread in china. According to statistics, the high-hardness granite is mainly distributed on mountainous regions and is intensively distributed on second and third grade terrain steps in the east of Yunobile plateau and Yanshan mountain range. The total area of harder carbonate rocks reaches 200 kilo-square kilometers, wherein the area of exposed carbonate rocks is about 130 kilo-square kilometers, and accounts for 1/7 of the total area of the country; the area of buried carbonate rock was about 70 kilo-square kilometers. The areas of the hard rocks in the provinces of cloud, precious, Sichuan, Shuangguang, Fujian and the like are more than those in other provinces. Taking the local of Liuzhou as an example, the hard rock area generally accounts for more than 80% of the construction area, the machine generally contacts the rock about 4 meters underground in the piling process, the depth of the rock stratum is generally about 20 meters, and the thickness of part of the rock stratum can reach more than 50 meters. The cutting picks have different qualities, the common piling depth is about 5-10 meters, the cutting picks can be damaged and need to be replaced, and the consumption of the cutting picks is huge.

The cutting pick mainly comprises a hard alloy head and a cutting pick body. The initial production process is as follows: firstly, forging and forming a blank; then carrying out incomplete annealing or spheroidizing annealing; then carrying out machining and then carrying out quenching and tempering heat treatment; derusting, mainly using acid cleaning; brazing the hard alloy; then grinding the teeth, and finally performing oil coating protection. The process is carried out by quenching and tempering and then brazing, and no post-treatment is carried out after brazing. The hardness of the matrix within 30mm from the tooth tip is reduced due to annealing, the hardness is less than 20HRC, and coarse widmannstatten structures and even overburnt structures can be generated, so that the comprehensive mechanical property of the matrix is greatly reduced. In order to make the cutting pick have a working part with higher hardness, researchers propose a scheme for comprehensively reforming the production process of the cutting pick: the method comprises the following steps of blanking a pick body, forging, machining, brazing a hard alloy pick tip, performing quenching and tempering heat treatment on the whole pick or performing isothermal quenching under a salt bath condition, and finally performing surface corrosion prevention treatment. Quenching and tempering heat treatment of the whole cutting pick or isothermal quenching under salt bath conditions is a necessary step for improving the toughness of the pick body and the wear resistance of the surface at the head of the pick body. However, in the heating and cooling processes of quenching and tempering heat treatment (quenching and high-temperature tempering treatment) and isothermal quenching under salt bath conditions, microcracks occur in the brazing seams and the hard alloy, and the service life of the cutting pick is damaged. When the tip of the tooth body is heated vigorously during brazing, internal cracks of the cemented carbide also grow, and a hot structure is generated at the tip of the tooth body. In addition, the wear resistance of the surface of the head of the hard alloy pick body is not obviously improved by carrying out quenching and tempering heat treatment or isothermal quenching on the whole pick body, so that the surface of the head of the pick body is worn at an early stage in the using or using process, the hard alloy is exposed prematurely and falls off, and the pick is rapidly worn and damaged.

At present, the production process of cutting picks in China mainly comprises the following 2 processes: (1) machining and forming a pick body, brazing the hard alloy head, heating by using a salt furnace, carrying out isothermal quenching under the condition of nitrate, and carrying out tempering treatment. (2) Forming a cutting pick body, heating by a salt furnace, carrying out isothermal quenching under the condition of nitrate, cleaning, brazing a hard alloy head, and carrying out tempering treatment. In the production process of the type (1), the hard alloy head is brazed, then is heated in a salt furnace and is quenched at the same temperature under the condition of nitrate, so that the hardness of the cutting pick body is ensured, but the hard alloy head is heated twice in the processes of brazing and isothermal quenching under the condition of nitrate, so that the hard alloy head is embrittled, and the use time of the cutting pick is greatly shortened due to the cracking of the hard alloy head and the cracking generated by welding the hard alloy head and the cutting pick body in the process of using the cutting pick. For the production process of the type (2), the hard alloy head is brazed after isothermal quenching is carried out under the condition of nitrate, the hardness of the head of the cutting pick body is reduced, the wear resistance of the head of the cutting pick body is reduced although the quality of the hard alloy head and a welding seam is ensured, so that the hard alloy head is frequently and prematurely fallen off during the working of the cutting pick, and the service life of the cutting pick is greatly reduced. In order to meet the requirements for production and development and to meet the requirements for new mining machinery, processes are often used which improve the wear resistance and prolong the service life of the cutting pick, such as: (1) processing the cutting teeth by adopting a thermal spraying technology; (2) processing the cutting teeth by adopting a surfacing technology; (3) and processing the cutting pick by adopting a plasma cladding technology.

Adopting the prior process, forging and machining a 42CrMo stainless steel bar to obtain a cutting tooth body, quenching the cutting tooth body, heating the cutting tooth body to 850 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 60min, and then placing the cutting tooth body in quenching oil to cool to room temperature; then tempering the cutting tooth, heating the quenching cutting tooth body to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 60min, and then placing the quenching cutting tooth body in the air to cool to the room temperature. The hardness of the cutting pick body obtained by the process is 33.7HRC at room temperature and 27HRC at 600 ℃ measured by a Rockwell hardness tester. For the firmness factor f =12 formation, the work failed for 6min due to wear.

The current general level in China still lags behind and imports manufacturers. The method can be applied to low-end markets and the conditions with low requirements on working conditions, and occupies a considerable part of markets due to the cost advantage. The cutting pick required by high-end markets, particularly hard rock stratums, is still far from foreign countries. Therefore, on the basis of the existing 42CrMo cutting pick body, the components and the heat treatment process are further optimized, and the method has important significance for improving the hardness and the wear resistance of the cutting pick body.

Disclosure of Invention

The invention aims to solve the problems in the prior art, provides a cutting pick body heat treatment process which is simple in process and convenient to operate and can greatly improve the hardness and the wear resistance of a cutting pick body, and the invention is based on 42CrMo, controls the appearance and the distribution of a hard phase by adjusting the relative contents of C, Cr and Mo elements and quenching and tempering processes and adjusting the hardness of alloy through carbon content, improves the high-temperature strength of the cutting pick body and effectively overcomes the defects of the hardness and the wear resistance of the existing cutting pick.

The technical scheme adopted by the invention for realizing the purpose is as follows: a cutting pick body heat treatment process comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1-3 parts of Cr and 0.5-2 parts of Mo to carry out alloying;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000-1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the pick tooth body obtained in the step S3 to 730-950 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing the pick tooth body in emulsion or liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 250-450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing in air to cool to room temperature.

The further technical scheme of the invention is as follows: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1 part of Cr and 2 parts of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 750 ℃ at a heating rate of 5 ℃/min, then preserving heat for 60min, and then placing the cutting tooth body in an emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching cutting tooth body obtained in the step (S4) to 250 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing in air to cool to room temperature.

The further technical scheme of the invention is as follows: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 2 parts of Cr and 1 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 950 ℃ at a heating rate of 5 ℃/min, preserving heat for 90min, and then placing the cutting tooth body in liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 90min, and then placing in the air to cool to room temperature.

The further technical scheme of the invention is as follows: the method comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 3 parts of Cr and 0.5 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1200 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 850 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing the cutting tooth body in emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 60min, and then placing in the air to cool to room temperature.

The heat treatment process for the cutting pick body has the following beneficial effects due to the adoption of the scheme:

1. the heat treatment process of the cutting pick tooth body is based on 42CrMo, the hardness of alloy is adjusted through adjusting the relative contents of C, Cr and Mo elements and quenching and tempering processes, the appearance and distribution of a hard phase are controlled, and the high-temperature strength of the tooth body is improved; controlling the size, quantity and distribution of hard precipitated phases by adjusting quenching and tempering processes;

2. the quenching medium adopts the emulsion and the liquid nitrogen, so that the cooling rate is greatly improved compared with that of the traditional oil cooling, the rapid and complete transformation of the matrix tissue is promoted, and the internal stress and the performance deterioration caused by the residual untransformed tissue are reduced;

3. the tempering temperature is increased to 250-450 ℃, the speed of precipitated phases is regulated and controlled, the size and distribution of the precipitated phases are controlled, the quenching residual stress is eliminated, and the toughness and the hardness of the quenched phases are matched.

The heat treatment process of a cutting pick body according to the present invention will be further described with reference to examples.

Detailed Description

The first embodiment is as follows:

a cutting pick body heat treatment process comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1-3 parts of Cr and 0.5-2 parts of Mo to carry out alloying; according to the invention, by increasing the content of Cr and Mo elements in the tooth body, Fe and Cr elements can be combined with carbon to form more hard Fe3C and chromium carbide hard precipitated phases, and Mo element can adjust thermodynamics and kinetics of the precipitated phases through solid solubility change, and simultaneously can improve high-temperature stability and reduce softening phenomenon in a high-temperature service process;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000-1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the pick tooth body obtained in the step S3 to 730-950 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing the pick tooth body in emulsion or liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 250-450 ℃ at a heating rate of 5 ℃/min, preserving heat for 30-90 min, and then placing in air to cool to room temperature.

The invention relates to a cutting pick tooth body heat treatment process, which is based on that the Ac1 temperature of 42CrMo alloy steel is 730 ℃, the Ac3 is 780 ℃, the Ar1 is 690 ℃, the Ms is 360 ℃, new component alloy after smelting and casting is heated to 730-950 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 30-90 min, then the new component alloy is placed in emulsion or liquid nitrogen to be cooled to the room temperature, then is heated to 250-450 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 30-90 min, and then is air-cooled to the room temperature. Heating the pick body to a temperature above a critical point during quenching to fully austenitize the internal structure of the pick body, and then rapidly cooling the pick body by corresponding cooling liquid to convert the structure of the pick body into martensite; after quenching is finished, a large amount of residual stress exists in the cutting pick body, and the toughness of martensite is extremely poor, so that the quenched cutting pick body cannot be directly used, in order to obtain more comprehensive performance of the quenched cutting pick body, tempering treatment must be carried out on the quenched cutting pick body, and the main purpose of tempering is to eliminate the quenching residual stress and enable the toughness and the hardness of the tempered cutting pick body to be matched.

Compared with the tooth body processed by the traditional process, the tooth body processed by the process has room temperature hardness of more than or equal to 50 HRC and high temperature hardness of more than or equal to 45HRC, the room temperature hardness of the product is improved by more than 50%, and the service life of the product under the working condition of the ultrahard rock stratum is prolonged by 3-6 times.

Example two:

a cutting pick body heat treatment process comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 1 part of Cr and 2 parts of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1000 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 750 ℃ at a heating rate of 5 ℃/min, then preserving heat for 60min, and then placing the cutting tooth body in an emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching cutting tooth body obtained in the step (S4) to 250 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing in air to cool to room temperature.

The pick body obtained in this example had a hardness of 42.1HRC at room temperature and 33.4HRC at 600 ℃ as measured by a Rockwell hardness tester; for the formation with firmness factor f =12, 13min of operation failed due to wear.

Example three:

a cutting pick body heat treatment process comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 2 parts of Cr and 1 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1500 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 950 ℃ at a heating rate of 5 ℃/min, preserving heat for 90min, and then placing the cutting tooth body in liquid nitrogen to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 90min, and then placing in the air to cool to room temperature.

The pick body obtained in this example had a room temperature hardness of 47.3HRC as measured by a Rockwell hardness tester and a hardness of 38.9HRC at 600 ℃; for a formation with a firmness factor of f =12, the operation was failed for 22min due to wear.

Example four:

a cutting pick body heat treatment process comprises the following steps:

s1, smelting: melting 42CrMo stainless steel as a raw material into molten carbon steel by an electric furnace, and then adding 3 parts of Cr and 0.5 part of Mo to alloy the molten carbon steel;

s2, casting: casting the carbon molten steel obtained in the step S1 into a stainless steel bar at the casting temperature of 1200 ℃;

s3, molding: forging and pressing the stainless steel bar, and machining to form a rectangular cutting pick body;

s4, quenching: heating the cutting tooth body obtained in the step S3 to 850 ℃ at the heating rate of 5 ℃/min, then preserving heat for 30min, and then placing the cutting tooth body in emulsion to cool to room temperature;

s5, tempering: and (4) heating the quenching pick tooth body obtained in the step (S4) to 450 ℃ at the heating rate of 5 ℃/min, preserving the heat for 60min, and then placing in the air to cool to room temperature.

The hardness of the pick body obtained in this example, as measured by a Rockwell hardness tester, was 52HRC at room temperature and 47HRC at 600 ℃; for a rock formation with a firmness factor of f =12, work failed for 35min due to wear; compared with the cutting pick body processed by the prior art, the hardness of the cutting pick body is improved by 40 percent, and the service life of the cutting pick body under the working condition of the ultrahard rock stratum is improved by nearly 6 times.

The above embodiments are only preferred embodiments of the present invention, and the structure of the present invention is not limited to the forms of the above embodiments, and any modifications, equivalents and the like within the spirit and principle of the present invention should be included in the protection scope of the present invention.