CN101693943A - High speed steel tool heat treatment method - Google Patents

Abstract

The invention relates to a high speed steel tool heat treatment method and the method specifically includes the following steps: high-temperature step quenching steel materials to be treated in a quenching medium at the temperature of 1200-1310 DEG C; after quenching, cooling to room temperature and then low-temperature tempering for 1h at the temperature of 80-100 DEG C; cold treating for 2-3h at the temperature of minus 120-minus 80 DEG C; and finally tempering for 1-1.5h at the temperature of 540-560 DEG C, wherein the quenching medium is selected from calcium chloride saturated water solution, polyglycol water solution, polyving akohol water solution or potassium permanganate quenching liquid. The high speed steel tool heat treatment method is simple in process and saves energy, and compared with traditional technology, the mechanical performance and service life of the high speed steel tool are improved by around 20-40 percent.

Description

Heat treatment method for high-speed steel cutting tools

technical field

The invention relates to a heat treatment method for steel materials, in particular to a heat treatment method for high-speed steel cutting tools.

Background technique

At present, the high-speed steel cutting tools widely used in my country are mainly tungsten-based W18Cr4V (abbreviated as 18-4-1) steel and tungsten-molybdenum-based W6Mo5Cr4V2 (abbreviated as 6-5-4-2) steel. There are two main heat treatment processes for these two steels: one is the traditional heat treatment process: after high temperature quenching, it needs to be tempered three times within the first hardening range; the other is cryogenic treatment process: high temperature quenching, one tempering and then put into cryogenic medium (Liquid nitrogen at -196°C) for a period of time and then tempered two to three times. With the traditional heat treatment process, the red hardness (hardness performance at high temperature of cutting) of high-speed steel cutting tools is poor. Although the cryogenic treatment process can achieve high hardness, high red hardness and high wear resistance, it usually requires multiple tempering and the cryogenic temperature is relatively low, which is not ideal from the perspective of energy saving and production cost.

Contents of the invention

The purpose of the present invention is to provide a heat treatment method for high-speed steel cutting tools to overcome the above-mentioned defects in the prior art.

The heat treatment method of the high-speed steel cutting tool of the present invention comprises the following steps:

The steel material to be treated is quenched in a quenching medium at a temperature of 1200-1310°C; after quenching, it is cooled to room temperature, and then tempered at a low temperature of 80-100°C for 1 hour; cold treatment at -120-80°C for 2-3 hours; Tempering at ℃ for 1 hour;

The quenching medium is selected from saturated calcium chloride aqueous solution, polyglycol aqueous solution, polyvinyl alcohol aqueous solution or potassium permanganate quenching liquid, preferably organic quenching liquids such as polyglycol aqueous solution and polyvinyl alcohol aqueous solution;

The staged quenching refers to: two staged quenching methods of successively lowering the temperature, and the staged temperatures of the staged quenching are generally 600-650°C and 500-550°C.

The steel material is preferably high-speed steel rolled from small ingots.

Preferably cold treatment is performed at a temperature range of -110 to -90°C for 2 to 3 hours.

When the steel material is W18Cr4V, the quenching heating temperature is 1260-1300°C.

When the steel material is W6Mo5Cr4V2, the quenching heating temperature is 1200-1240°C.

Since the final martensitic transformation point Mf of high-speed steel is very low, for example, the Mf point of W18Cr4V steel is about ~100°C, so a large amount of austenite will remain after quenching and cooling to room temperature, and the remaining austenite in steel is Harmful, it will reduce the hardness, wear resistance and service life of steel. Now put the high-speed steel tool after quenching and cooling in the temperature range of -120 ~ -80 ° C, then a large amount of retained austenite will be transformed into martensite; at the same time, the high-speed steel tool will have a volume effect, that is, the supersaturated metastable martensite The superfine carbide particles are partially decomposed and dispersed on the dislocation plane, and the size is only 30-60A and maintains a coherent relationship with the matrix. The ultrafine carbide particles are large and uniformly dispersed, such as W18Cr4V steel after cold treatment After that, the carbide particles increased by about 8%, and the carbide particles precipitated by W6Mo5Cr4V2 steel increased by about 36%, and the matrix structure was also obviously refined. Since the precipitated ultrafine carbide particles are evenly distributed on the martensite matrix, the catalytic effect of the grain boundary is weakened, and the refinement of the matrix structure also weakens the degree of segregation of impurity elements at the grain boundary, which plays a role in strengthening the grain boundary. The mechanical properties of high-speed steel are improved, and the hardness, red hardness and wear resistance are greatly improved. For example, the hardness is increased from 60-61HRC to 62-63HRC, the red hardness and wear resistance are greatly improved (about 20-40% higher than the traditional process), and the mechanical performance indicators are close to cryogenic treatment. In addition, cold treatment, like cryogenic treatment, improves the performance of high-speed steel cutting tools as a whole, so high-speed steel cutting tools can be repaired and used after cutting and wear.

Detailed ways

The quenching equipment can be a salt bath furnace or a vacuum furnace, etc. The salt bath furnace is preferred for quenching in the present invention. The salt bath furnace is used because the heating medium of the salt bath furnace is liquid molten salt, so the heating speed is fast and uniform, the workpiece is less oxidized and decarburized, and the deformation can be reduced. When quenching and heating, there should be a certain gap between the knives, and they should not be too tightly packed to ensure that the knives are fully hardened.

The cold treatment equipment can be a cold treatment room or a low-temperature cold treatment box, as long as the temperature of the equipment can reach -120～-80°C, it can be used as a cold treatment equipment. For example, use the -120 degree industrial low temperature treatment box produced by Wuxi Shengze Physical and Chemical Equipment Co., Ltd., model: GY-A215.

In the selection of materials to be processed, since high-speed steel is a ledeburite steel containing a large amount of alloy elements, there will be a large number of primary eutectic carbides and secondary carbides after smelting. These carbides are hard and brittle, which can lead to stress concentration and become Quenching cracks. Therefore, it is best to choose the raw material for billet rolling of small steel ingots; unqualified raw materials should be forged to crush the eutectic carbide in the material, so that the unevenness of the eutectic carbide is less than or equal to 3 grades;

The quenching step must adopt the pretreatment process of high temperature graded quenching. For large tools, due to the difference in temperature between the surface and the center, the temperature difference will cause the volume expansion and contraction to be different, resulting in quenching internal stress. The quenching cooling medium (such as calcium chloride saturated aqueous solution, polyglycol aqueous solution, polyvinyl alcohol aqueous solution, potassium permanganate quenching liquid, etc.) which is cooled slowly below the martensite is used as the quenching cooling medium.

The temperature of cold treatment is within the temperature range of -120 ~ -80 ℃, and there is no need to further reduce it, because the increase in hardness and red hardness is not obvious except that the wear resistance is slightly improved when the temperature is lowered. After cold treatment, it is best to put the tool in room temperature water to heat up, so as to eliminate the secondary quenching stress of cold treatment.

Tempering should be tempered in protective atmosphere furnaces, vacuum electric furnaces and fully deoxidized salt bath furnaces to prevent oxidative decarburization; it can also be tempered in low temperature (≤100°C) furnaces, and slowly increase the temperature to ≥300°C and then The furnace is heated to the required tempering temperature of 550°C, and then the furnace is air-cooled to room temperature. During the air cooling process, water cooling and oil cooling should be avoided to prevent large secondary quenching stress.

Example 1

机用丝锥.热处理工艺为：淬火(加热温度1200-1240℃保温2小时，在600-650℃和500-550℃二级淬火至室温)→低温回火(80-100℃低温回火1小时)→-110～-90℃冷处理2～3小→最后550±10℃回火1小时；Made of W6Mo5Cr4V2 high speed steel

Machine taps. The heat treatment process is: quenching (heating temperature 1200-1240 ° C for 2 hours, secondary quenching at 600-650 ° C and 500-550 ° C to room temperature) → low temperature tempering (80-100 ° C low temperature tempering for 1 hour )→-110～-90℃ cold treatment for 2～3 hours→finally tempering at 550±10℃ for 1 hour;

The comparative experiment adopts the traditional process (one quenching and three tempering) and cryogenic treatment process.

The processed taps are installed on the drill floor. The processed material is 40Cr steel, the hardness is 190HB, the cutting speed is 5.2m/min, the cutting depth is 6mm, and the flow rate of coolant (emulsion) is 5L/min. After testing it was found that: The high-speed steel tap uses the traditional process to process an average of 45.2 holes, an average of 62.2 holes after cryogenic treatment, and an average of 61.8 holes after cold treatment. It can be seen that the service life of the tap after the cold treatment is 36.7% higher than that of the traditional process, and it is comparable to the service life of the cryogenic treatment.

Example 2

Made of W18Cr4V high speed steel Twist drill bit. The heat treatment process is: quenching (heating temperature 1260-1300 ° C for 2 hours, secondary quenching at 600-650 ° C and 500-550 ° C to room temperature) → low temperature tempering (80-100 ° C low temperature tempering for 1 hour) →-120～-80℃ cold treatment for 2～3 hours; finally tempering at 550±10℃ for 1.5 hours;

The comparative experiment adopts the traditional process (one quenching and three tempering) and cryogenic treatment process.

麻花钻头未经冷处理可加工27.8个孔，深冷处理后可加工40.2个孔，冷处理后可加工39.9个孔。由此可见冷处理后麻花钻头的使用寿命比传统工艺提高43.5％、与深冷处理的使用寿命不下上下。The treated twist drill bit is installed on the drill floor of Z305 drilling machine. The processed material is 1Cr18Ni9Ti stainless steel, the hardness is 200HB, the cutting speed is 4.8m/min, the drilling depth is 7mm, and the coolant flow rate is 5L/min. After testing it was found that:

The twist drill can process 27.8 holes without cold treatment, 40.2 holes after cryogenic treatment, and 39.9 holes after cold treatment. It can be seen that the service life of the twist drill after cold treatment is 43.5% higher than that of the traditional process, and it is comparable to the service life of cryogenic treatment.

Claims (5)

1. high speed steel tool heat treatment method is characterized in that, comprises the steps:

Pending steel is high temperature grading quenching in quenchant under 1200～1310 ℃ of temperature; The quenching postcooling is to room temperature, and 80～100 ℃ of low-temperaturetemperings are 1 hour again;-120～-80 ℃ of deepfreezes 2～3 hours; Last 540～560 ℃ of tempering 1～1.5 hour;

Described quenchant is selected from calcium chloride saturated aqueous solution, the polyglycol aqueous solution, polyvinyl alcohol water solution or potassium permanganate hardening liquid.

2. method according to claim 1 is characterized in that, steel is the rolling rapid steel of little steel ingot cogging.

3. method according to claim 1 is characterized in that, the deepfreeze temperature is-110～-90 ℃.

4. method according to claim 1 is characterized in that, when steel was W18Cr4V, quenching temperature was 1260～1300 ℃.

5. method according to claim 1 is characterized in that, when steel was W6Mo5Cr4V2, quenching temperature was 1200～1240 ℃.