阅读说明：本技术 一种铁基耐磨涂层犁铲尖的热处理方法 (Heat treatment method of iron-based wear-resistant coating plough shovel tip ) 是由 杨志荣 闫德胜 戎利建 吴宪吉 胡小锋 于 2019-09-16 设计创作，主要内容包括：本发明涉农机具的生产加工领域,具体地说是一种铁基耐磨涂层犁铲尖的热处理方法。该方法以硼钢材料犁铲尖为基体,采用等离子喷焊技术在犁铲尖基体上涂敷铁基耐磨层。将等离子喷焊有耐磨层的犁铲尖采用感应加热的方式加热至奥氏体化温度以上保温一定时间后迅速转入盐浴中淬火,淬火后犁铲尖置于空气中冷却,利用材料特性实现自回火。采用本发明生产的犁铲尖,可基本避免耐磨层淬火二次开裂,生产成本低,批次稳定好。经此热处理后耐磨层硬度63HRC以上,基体硬度45HRC以上,基体冲击韧性(akv)达到30J/cm<Sup>2</Sup>,产品性能和使用寿命大幅度高于国内同类产品。(The invention relates to the field of production and processing of agricultural machinery, in particular to a heat treatment method of a plough shovel tip with an iron-based wear-resistant coating. The method takes a boron steel material plough shovel tip as a matrix, and adopts a plasma spray welding technology to coat an iron-based wear-resistant layer on the plough shovel tip matrix. Heating the plough shovel tip with the wear-resistant layer sprayed and welded on by plasma to be above the austenitizing temperature by adopting an induction heating mode, preserving heat for a certain time, then quickly transferring into a salt bath for quenching, cooling the plough shovel tip in air after quenching, and realizing self-tempering by utilizing the material characteristics. The plough shovel tip produced by the invention can basically avoid the secondary cracking of the wear-resistant layer during quenching, and the productionLow cost and good batch stability. After the heat treatment, the hardness of the wear-resistant layer is more than 63HRC, the hardness of the matrix is more than 45HRC, and the impact toughness (akv) of the matrix reaches 30J/cm 2 The product performance and the service life are greatly higher than those of domestic similar products.)

1. A heat treatment method of a plow share with an iron-based wear-resistant coating is characterized in that boron steel is selected as a plow share base material, when quenching is carried out in a medium with a low cooling speed, the plow share base is cooled to below Ms point to obtain a complete quenching structure and realize self-tempering, and simultaneously, the wear-resistant layer of the plow share is ensured not to have quenching cracking;

wherein the quenching medium used by the iron-based wear-resistant layer plough shovel tip is 50 wt% KNO₃+50wt％NaNO₂Molten salt, the melting point of the quenching medium is lower than 140 ℃.

2. The heat treatment method of the iron-based wear-resistant coating plough shovel tip as claimed in claim 1, characterized in that the iron-based wear-resistant coating plough shovel tip is heated to 880-920 ℃ by induction heating, immediately quenched into molten salt at 200-260 ℃ and kept for 1-2 min, and completely cooled to the same temperature as the quenching medium, and then air-cooled.

3. The method for heat treating an iron-based wear-resistant coated plow blade tip as defined in claim 2, wherein the self-tempering is carried out by using the residual heat of the iron-based wear-resistant coated plow blade tip to improve the toughness of the substrate and to eliminate a part of the quenching stress.

4. The method for heat-treating a plow tip having an iron-based wear-resistant coating as defined in claim 2, wherein the technical means are obtained after the heat treatmentThe notation is as follows: the hardness of the wear-resistant layer is more than 63HRC, the hardness of the matrix is more than 45HRC, and the impact toughness (akv) of the matrix reaches 30J/cm²The above.

5. The method for heat-treating the plow tip of the iron-based wear-resistant coating of claim 1, wherein the iron-based wear-resistant coating comprises the following chemical components in percentage by weight: 3.2 to 3.5 of C, 2.7 to 3.5 of Si, 25 to 28 of Cr, 1.5 to 2 of B and the balance of Fe.

The technical field is as follows:

the invention relates to the field of production and processing of agricultural machinery, in particular to a heat treatment method of a plough shovel tip with an iron-based wear-resistant coating.

Background art:

along with the rapid development of agricultural technology and the continuous improvement of mechanization and automation degree, in the process of realizing agricultural modernization, agricultural machinery is more and more valued by the nation, and agricultural machinery cutters, for example: a plough shovel tip, a plough share, a hoe shovel, a rotary cultivator blade and the like are key parts of agricultural machinery and are important process links for ensuring safe and excellent operation of the agricultural machinery in a life cycle. The agricultural machinery soil-contacting working parts have the disadvantages of severe working conditions, complex working conditions and high possibility of abrasion, and the abrasion-resistant layer is required to have high hardness and toughness, and the matrix has high toughness.

The plow tip is the most representative member of penetration. In order to enhance the wear resistance of the plough shovel tip and prolong the service life, agricultural machinery manufacturers often adopt a mode of coating a wear-resistant layer on the surface to achieve the purpose of improving the product quality. However, the surface coating process needs to be completed under high temperature, and the structure of the plough shovel point base material is changed into: pearlite + ferrite, generally with a hardness below 20 HRC. The abrasion-resistant layer of the plough shovel tip is mostly formed by coating iron-based materials with lower cost, is essentially a high-chromium cast iron material, and has the characteristics of high hardness, large brittleness, easy cracking and the like. If the plough shovel tip is subjected to conventional quenching treatment after being coated with the wear-resistant layer, the wear-resistant layer can crack, peel and the like; if the plow shovel tip is not quenched after being coated with the wear-resistant layer, the service performance of the plow shovel tip is seriously reduced, and the problems of deformation, quick wear, low working efficiency and the like can occur.

The invention content is as follows:

the invention aims to provide a heat treatment method of a plough shovel tip with an iron-based wear-resistant coating, which can ensure that a wear-resistant layer of the plough shovel tip does not crack after quenching, does not reduce the performance of a welded material of the wear-resistant layer, and can ensure that a basal body of the plough shovel tip obtains higher toughness.

The technical scheme of the invention is as follows:

a heat treatment method of a plow blade with an iron-based wear-resistant coating is characterized in that boron steel is selected as a plow blade tip matrix material, when quenching is carried out in a medium with a low cooling speed, the plow blade tip matrix is cooled to below Ms point to obtain a complete quenching structure and realize self-tempering, and simultaneously, the wear-resistant layer of the plow blade tip is ensured not to have quenching cracking phenomenon;

wherein the quenching medium used by the iron-based wear-resistant layer plough shovel tip is 50 wt% KNO₃+50wt％NaNO₂Molten salt, the melting point of the quenching medium is lower than 140 ℃.

According to the heat treatment method of the iron-based wear-resistant coating plough shovel tip, the iron-based wear-resistant coating plough shovel tip is heated to 880-920 ℃ in an induction heating mode, then is immediately quenched into molten salt at 200-260 ℃ and is kept for 1-2 min, so that the temperature of the iron-based wear-resistant coating plough shovel tip is completely reduced to be the same as that of a quenching medium, and then air cooling is carried out.

The heat treatment method of the iron-based wear-resistant coating plough shovel tip utilizes the waste heat of the iron-based wear-resistant coating plough shovel tip to realize self tempering, improve the toughness of a matrix and eliminate part of quenching stress.

The heat treatment method of the iron-based wear-resistant coating plough shovel tip obtains the following technical indexes after heat treatment: the hardness of the wear-resistant layer is more than 63HRC, the hardness of the matrix is more than 45HRC, and the impact toughness (akv) of the matrix reaches 30J/cm²The above.

The iron-based wear-resistant coating comprises the following chemical components in percentage by weight: 3.2 to 3.5 of C, 2.7 to 3.5 of Si, 25 to 28 of Cr, 1.5 to 2 of B and the balance of Fe. The chemical components of the plough shovel tip basal body are as follows according to weight percentage: 0.28-0.32% of C, 1.0-1.5% of Mn1.17-0.37% of Si, less than 0.45% of Cr, less than 0.05% of Ti, less than 0.06% of Al, less than 0.25% of Cu, less than 0.035% of P, less than 0.035% of S, 0.0008-0.0030% of B and the balance of Fe. And coating an iron-based wear-resistant layer on the plough shovel tip matrix by adopting a plasma spray welding technology according to the components.

The design idea of the invention is as follows:

the metallographic structure matrix of the wear-resistant coating is a martensite structure, and a large amount of Cr is uniformly distributed in the structure₇C₃And a small amount of Cr₂₃C₆A hard particle phase; during quenching, the austenitizing temperature is 880-920 ℃, hard point phases in the wear-resistant coating are not decomposed, and the heat preservation time is short, so that the tissue type and the hard point phase form in the wear-resistant coating are not changed before and after quenching; the Ms point of the material of the base body of the plough shovel point is higher than 370 DEG CThe temperature of the quenched workpiece is the same as that of the salt bath and is 200-260 ℃, and by utilizing the characteristic, waste heat self-tempering can be realized, the toughness of the matrix is improved, and part of quenching stress is eliminated; the metallographic structure of the wear-resistant coating is not changed in the self-tempering process of the plough shovel tip matrix, partial stress in the wear-resistant coating can be released, and the quality stability of the wear-resistant coating is improved.

The invention has the characteristics and beneficial effects that:

1. after the iron-based wear-resistant layer plough shovel tip is subjected to salt bath quenching, secondary cracking of the wear-resistant layer during quenching can be basically avoided, and the appearance and the overall quality of the plough shovel tip are ensured. The assessment result of the plough shovel tip for actual production operation can reach the international advanced level, and a good assessment result is obtained.

2. The plough shovel tip produced by the invention has low production cost and good batch stability. After the heat treatment, the hardness of the wear-resistant layer is more than 63HRC, the hardness of the matrix is more than 45HRC, and the impact toughness (akv) of the matrix reaches 30J/cm²The product performance and the service life are greatly higher than those of domestic similar products.

Description of the drawings:

FIG. 1 is a metallographic structure diagram of an iron-based wear-resistant layer spray-welded according to test components;

FIG. 2 is a tissue diagram of a plow shovel tip matrix after 200 ℃ salt bath quenching;

FIG. 3 is an appearance diagram of the wear-resistant coating after water-cooling quenching of the plough shovel tip;

FIG. 4 is an appearance diagram of the wear-resistant coating after 160 ℃ salt bath quenching of the plough shovel tip;

FIG. 5 is an appearance diagram of the wear-resistant coating after 200 ℃ salt bath quenching of the plough shovel tip.

The specific implementation mode is as follows:

in the specific implementation process, the boron steel material plough shovel tip is used as a matrix, and the plasma spray welding technology is adopted to coat an iron-based wear-resistant layer on the plough shovel tip matrix. Heating the plough shovel tip with the wear-resistant layer by adopting an induction heating mode to be above an austenitizing temperature, preserving heat for a certain time, then quickly transferring into a salt bath for quenching, cooling the plough shovel tip in air after quenching, and realizing self-tempering by utilizing the material characteristics.

The following test examples will further illustrate the invention, but do not limit it accordingly.

The spraying welding powder raw material of the plough shovel tip wear-resistant layer is purchased from the market, is prepared by adjusting the distribution ratio and automatically using a powder mixer, and the specific components are shown in table 1; the material composition of the plow tip base is shown in Table 2.

Table 1 abrasion resistant layer of the invention chemical composition (wt.%, balance Fe)

Element(s)	C	Si	Cr	B
					Content (wt.)	3.4	3.1	27.4	1.8

TABLE 2 chemical composition of the base material of the plough shovel tip of the present invention (wt.%, balance Fe)

Element(s)	C	Mn	Si	Cr	Al	Ti	B	P	S	Cu
											Content (wt.)	0.28	1.36	0.23	0.45	0.01	0.05	0.002	0.015	0.015	0.1

The invention is further proved by carrying out heat treatment in different cooling modes on the plough shovel tip model machine trial-manufactured by adopting the chemical components and raw materials and according to the test result and the comprehensive comparison of the appearance state of the sample after quenching. The salt bath used in the test was 50 wt% KNO₃+50wt％NaNO₂. In order to ensure the accuracy of the test, 10 samples of the same batch are randomly selected for quenching by the same heat treatment process in each example. Part of the heat treatment test protocol of the present invention is shown in table 3; the results and properties of the test parts of the present invention are shown in Table 4.

TABLE 3 some examples of the invention

Item	Number of samples	Quenching temperature	Time of heat preservation	Cooling method
					Example 1	10	890℃	30min	Cooling with water to below 50 deg.C
Example 2	10	890℃	30min	Cooling the oil to below 50 deg.C
					Example 3	10	890℃	30min	160 ℃ salt bath/2 min
Example 4	10	890℃	30min	200 ℃ salt bath/2 min
					Example 5	10	890℃	30min	230 ℃ salt bath/2 min
Example 6	10	890℃	30min	Salt bath at 260 deg.C/2 min
					Example 7	10	890℃	30min	300 ℃ salt bath/2 min

TABLE 4 test results and Properties of some examples of the invention

The above part of test results of the present invention show that:

the hardness of the wear-resistant layer is not influenced by a quenching mode, and the hardness after quenching is basically consistent;