CN108359785A - A kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches - Google Patents

Abstract

The invention discloses a strengthening and toughening treatment method for a W6Mo5Cr4V2 high-speed steel broach, which belongs to the technical field of alloy tool steel heat treatment technology. The specific steps are: firstly quenching the W6Mo5Cr4V2 high-speed steel broach in a salt bath; and high-temperature tempering twice; Then carry out salt bath nitrocarburizing treatment at a temperature of 540-550°C for 20-40 minutes; finally salt bath oxidation treatment at a temperature of 350-380°C for 20-30 minutes, take out the furnace and cool to room temperature; repeat the salt bath The nitriding and salt bath oxidation steps are repeated multiple times to increase the depth of the diffusion layer. The invention increases the strength and toughness of the W6Mo5Cr4V2 high-speed steel broach, significantly increases the penetration layer depth, effectively improves the surface hardness of the broach, and increases the service life of the broach by 2 to 4 times; The abrasiveness is better than that of the existing one-time nitriding treatment.

Description

A Strengthening and Toughening Treatment Method for W6Mo5Cr4V2 High Speed Steel Broach

technical field

The invention belongs to the technical field of alloy tool steel heat treatment technology, and in particular relates to a strengthening and toughening treatment method for a W6Mo5Cr4V2 high-speed steel broach.

Background technique

W6Mo5Cr4V2 high-speed steel is widely used to manufacture various types of non-standard broaches, such as spline broaches, round broaches, and keyway broaches, due to its high hardness, high wear resistance, good thermal stability, red hardness, and moderate price And polygon broaches, etc. The modern manufacturing and processing industry has put forward the requirements of high cutting speed, high precision, long life and good reliability for high-speed steel cutting tools. Toughness, thereby prolonging the life of high-speed steel tools and reducing production costs. There are two main methods to improve the strength and toughness of high-speed steel: 1. Adjust the chemical composition of high-speed steel or improve the heat treatment process to improve the strength and toughness of high-speed steel itself. 2. High-speed steel surface strengthening treatment, developing hard-core and tough high-speed steel cutting tools, such as surface coating technology, laser or ion beam surface strengthening treatment, nitriding, vulcanization, molybdenum, multi-component co-infiltration and other surface chemical heat treatment technologies.

Chinese invention patent (publication number CN 103805890A) discloses a heat treatment process of high-speed steel for cutting tools, Chinese invention patent (publication number CN 101693943A) discloses a high-speed steel tool heat treatment method, Chinese invention patent (publication number CN 103849739A) discloses A cryogenic treatment method for high-speed steel cutting tools. The three methods all change the size, shape and distribution of carbides in high-speed steel by adjusting the chemical composition of W6Mo5Cr4V2 high-speed steel or improving the heat treatment process, so as to improve the hardness of high-speed steel itself. However, the two key performance indicators of strength (hardness) and toughness of high-speed steel are contradictory, and the improvement of hardness is often at the expense of toughness.

In recent years, coated tools have developed rapidly. Depositing one or more layers of composite coatings on the surface of high-speed steel tools by physical or chemical methods can effectively improve the hardness and wear resistance of the tool, making the tool strong on the outside and tough on the inside. Features, can increase the service life of high-speed steel cutting tools by 3-6 times or more. Typical "hard" coating materials are diamond, TiC, TiN, TiCN, Al ₂ O ₃ and TiAlN. Chinese invention patent (publication number CN101591780) discloses a preparation method of wear-resistant coating for cutting tools, which is characterized in that N//TiN/TiC is formed on the surface of high-speed steel cutting tools from the inside to the outside by using the combined technology of plasma infiltration and deposition Multi-layer gradient composite coating. The multi-layer composite coating prepared by this method strengthens the high-speed steel cutting tool, which can improve the strength, hardness, wear resistance and service life of the cutting tool surface while maintaining the toughness of the cutting tool core. However, the existing coating technology cannot well solve the problem of low interface bonding strength between the coating and the substrate, and the coating is easy to peel off. Moreover, the regrindability of coated tools is poor, the equipment is expensive, the pretreatment process requirements are relatively strict, and the cost is high. It is suitable for expensive and precision tools, such as gear tools.

Chinese invention patent (publication number CN1594605A) discloses high-current pulsed ion beam treatment technology on the surface of high-speed steel tools, using high-current pulsed ion beam irradiation for surface treatment of high-speed steel tools, combined with subsequent cryogenic treatment to change the surface of high-speed steel tools Organization structure, improve the hardness and wear resistance of high-speed steel cutting tools, thereby increasing the service life of cutting tools. The superiority of this method is obvious to all, but it faces the same dilemma as other ion beam surface modification technologies such as laser surface treatment, and industrial production is difficult.

Chinese invention patent (publication number CN 1616705A) discloses the salt bath nitrocarburizing treatment of high-speed steel (W6Mo5Cr4V2) vanes (or blades), and Chinese invention patent (publication number CN 101871087A) discloses salt bath treatment of high-speed steel air-conditioning compressor blades. Salt bath formula and treatment method in bath nitriding treatment, these two methods are through salt bath nitriding treatment on W6Mo5Cr4V2 high speed steel, which can improve the surface hardness, wear resistance and service life of high speed steel. The salt bath nitrocarburizing treatment technology has low cost, remarkable strengthening effect and stable performance, and can also be applied to general-purpose high-speed steel tools with a large quantity and a wide range. The above high-speed steel surface strengthening treatment technology is to carry out subsequent treatment on the finished tool to improve its performance and service life. There are many process steps, and it is not ideal in terms of energy saving and production cost.

Contents of the invention

Purpose of the invention: In view of the problems existing in the prior art, the purpose of the present invention is to provide a strengthening and toughening treatment method for W6Mo5Cr4V2 high-speed steel broach, so that it has the characteristics of hard surface and tough core, which not only improves the comprehensive performance of the material, but also Greatly save energy and production costs.

In order to realize the above-mentioned purpose of the invention, the present invention adopts following technical scheme:

A method for strengthening and toughening a W6Mo5Cr4V2 high-speed steel broach, comprising the steps of:

Step 1, step quenching, obtain the high-speed steel broach after quenching;

Step 2, high-temperature tempering: Temper the quenched high-speed steel broach in a salt bath furnace, then air-cool to room temperature, and perform 2 tempering according to this process to obtain a high-speed steel broach after high-temperature tempering;

Step 3, salt bath nitriding: subjecting the high-speed steel broach after high temperature tempering to salt bath carbonitriding treatment;

Step 4. Salt bath oxidation: Put the high-speed steel broach after salt bath nitriding treatment into an oxide salt bath furnace, take it out of the furnace and cool to room temperature, and wash with water to remove the salt on the surface;

Step 5. Polishing: Polish the surface of the high-speed steel broach to remove the loose layer on the surface.

Step 6. Repeat the above steps 3, 4 and 5 for n times (n≥1), increase the depth of the infiltration layer, and obtain a high-speed steel broach with a hard surface and a tough core.

The staged quenching step in the described step one is as follows:

First, preheat the high-speed steel broach in an air furnace at 400-550°C for 2-4 hours at low temperature, then preheat it in a salt-bath furnace at 850-870°C for 10-20 minutes; then heat it in a high-temperature salt-bath furnace to the quenching temperature of 1200 ～1220℃, holding time 10～18s/mm; then quenching step by step in salt bath, temperature 500～550℃, time 10～18s/mm, to obtain high-speed steel broaches after quenching;

The temperature of the high temperature tempering in the step 2 is 560°C;

The salt bath nitriding step in the described step 3 is as follows:

1) Cleaning: Wash the high-speed steel broach with water to remove the salt on the surface;

2) Preheating: the preheating temperature is 350-400°C, and the time is 20-30 minutes. The purpose of preheating is to form a thin FeO film on the surface of the high-speed steel broach to promote subsequent nitriding;

3) Nitriding treatment: immerse the high-speed steel broach in a salt bath furnace at 540-550°C for nitrocarburizing treatment for 20-40 minutes.

In the third step, during the nitriding treatment, the CNO ^- concentration in the salt bath furnace is 30-32%.

The salt-bath oxidation step in the fourth step is: put the high-speed steel broach after salt-bath nitriding treatment into an oxidation salt-bath furnace at 350-380° C., and the oxidation time is 20-30 minutes.

Beneficial effects: compared with the prior art, after the present invention undergoes low-temperature salt bath nitriding and salt bath oxidation treatment, an oxide layer of Fe ₃ O ₄ and a diffusion layer of solid solution of nitrogen and carbon in α-Fe are formed on the surface of high-speed steel , effectively improving the surface hardness while maintaining the toughness of the broach core; at the same time, saving a 560°C high-temperature tempering process, the high-speed steel broach has undergone several salt bath nitriding treatments, and the penetration depth has increased significantly. The surface hardness of the broach is effectively improved, and the service life of the broach can be increased by 2 to 4 times; in addition, after a period of use of the broach, the regrinding property of the blade is better than that of the existing one-time nitriding treatment.

Description of drawings

Figure 1 is the XRD spectrum of the surface of W6Mo5Cr4V2 high speed steel;

Figure 2 is the gradient hardness value of W6Mo5Cr4V2 high-speed steel section.

Detailed ways

The technical solutions of the present invention will be described in detail below through the examples and in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the examples described.

A kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broach, its specific steps are as follows:

Step 1. Graded Quenching

First, preheat the high-speed steel broach in an air furnace at 400-550°C for 2-4 hours at low temperature, then preheat it in a salt-bath furnace at 850-870°C for 10-20 minutes; then heat it in a high-temperature salt-bath furnace to the quenching temperature of 1200 ～1220℃, holding time 10～18s/mm; then quenching step by step in salt bath, temperature 500～550℃, time 10～18s/mm, to obtain high-speed steel broaches after quenching;

Step two, high temperature tempering

Temper the quenched high-speed steel broach in a salt-bath furnace at 560°C for 1 hour, then air-cool to room temperature, and temper twice according to this process to obtain a high-speed steel broach after high-temperature tempering;

Step three, salt bath nitriding

The high-speed steel broach after high temperature tempering is subjected to salt bath carbonitriding treatment, the method is as follows:

1) Cleaning: Wash the high-speed steel broach with water to remove the salt on the surface;

2) Preheating: the preheating temperature is 350-400°C, and the time is 20-30 minutes. The purpose of preheating is to form a thin FeO film on the surface of the high-speed steel broach to promote subsequent nitriding;

3) Nitriding treatment: immerse the broach in a salt bath furnace at 540-550°C for nitrocarburizing treatment for 20-40 minutes. The CNO ^- concentration in the salt bath furnace is controlled at around 30-32%.

Step 4, salt bath oxidation

Put the broach after salt bath nitriding treatment into an oxide salt bath furnace at 350-380°C for 20-30 minutes, take it out of the furnace and cool to room temperature. Wash with water for 5-10 minutes to remove the salt on the surface.

Step five, polishing

Polish the surface of the high-speed steel broach to remove the loose layer on the surface.

Step 6. Repeat the above steps 3, 4 and 5 for n times (n≥1), increase the depth of the infiltration layer, and obtain a high-speed steel broach with a hard surface and a tough core.

Example 1

The strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel spline broach with a size of Φ30×900mm is as follows:

Step 1, graded quenching: Preheat the high-speed steel broach in an air furnace at 500°C for 2 hours at low temperature; preheat it in a salt bath furnace at 870°C for 10 minutes at medium temperature; heat it in a high temperature salt bath furnace to 1220°C for 5 minutes; then Quenching in stages in a salt bath at a temperature of 550°C for 5 minutes.

Step 2, high-temperature tempering: temper the quenched high-speed steel broach in a 560°C salt bath furnace for 1 hour, then air-cool to room temperature, and perform 2 tempering according to this process.

Step 3, salt bath nitriding: the high-speed steel broach obtained in step 2 is subjected to salt-bath carbonitriding treatment, the method is as follows: (1) cleaning: the high-speed steel broach is cleaned with water to remove the salt on the surface; (2 ) Preheating: the preheating temperature is 400°C, and the time is 20 minutes; (3) Nitriding treatment: the broach is immersed in a salt bath furnace at 540°C for nitrocarburizing treatment, and the time is 40 minutes. The CNO ^- concentration in the salt bath is controlled at about 32%.

Step 4, salt bath oxidation: Put the broach after salt bath nitriding treatment in a 350°C oxidation salt bath furnace for 30 minutes, take it out of the furnace and cool to room temperature. Wash with water for 5 minutes to remove the salt on the surface.

Step 5. Polishing: Polish the surface of the broach to remove the loose layer on the surface.

Step 6. Repeat the above steps 3, 4 and 5 once.

Example 2

The strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel spline broach with a size of Φ30×900mm is as follows:

Step 1: Grading quenching: Preheat the high-speed steel broach in an air furnace at 500°C for 2 hours at low temperature; preheat it in a salt bath furnace at 870°C for 10 minutes at medium temperature; heat it in a high temperature salt bath furnace to 1220°C for 5 minutes; then Quenching in stages in a salt bath at a temperature of 550°C for 5 minutes.

Step 2: Tempering at high temperature: Temper the quenched high-speed steel broach in a salt bath furnace at 560°C for 1 hour, then air-cool to room temperature, and perform tempering twice according to this process.

Step 3: salt bath nitriding: the high-speed steel broach obtained in step 2 is subjected to salt-bath carbonitriding treatment, the method is as follows: (1) cleaning: the high-speed steel broach is cleaned with water to remove the salt on the surface; (2 ) Preheating: the preheating temperature is 400°C, and the time is 20 minutes; (3) Nitriding treatment: the broach is immersed in a salt bath furnace at 540°C for nitrocarburizing treatment, and the time is 20 minutes. The CNO ^- concentration in the salt bath is controlled at about 32%.

Step 4: Salt bath oxidation: Put the broach after salt bath nitriding treatment in a 350°C oxidation salt bath furnace for 30 minutes, take it out of the furnace and cool to room temperature. Wash with water for 5 minutes to remove the salt on the surface.

Step 5: Polishing: Polish the surface of the broach to remove the loose layer on the surface.

Step 6. Repeat the above steps 3, 4, and 5 to perform surface toughening treatment twice to increase the depth of the seepage layer.

Example 3

The strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel spline broach with a size of Φ30×900mm is as follows:

Step 1: Grading quenching: Preheat the high-speed steel broach in an air furnace at 500°C for 2 hours at low temperature; preheat it in a salt bath furnace at 870°C for 10 minutes at medium temperature; heat it in a high temperature salt bath furnace to 1220°C for 5 minutes; then Quenching in stages in a salt bath at a temperature of 550°C for 5 minutes.

Step 2: Tempering at high temperature: Temper the quenched high-speed steel broach in a salt bath furnace at 560°C for 1 hour, then air-cool to room temperature, and perform tempering twice according to this process.

Step 3: salt bath nitriding: the high-speed steel broach obtained in step 2 is subjected to salt-bath carbonitriding treatment, the method is as follows: (1) cleaning: the high-speed steel broach is cleaned with water to remove the salt on the surface; (2 ) Preheating: the preheating temperature is 400° C., and the time is 20 minutes; (3) Nitriding treatment: the broach is immersed in a 550° C. salt bath furnace for nitrocarburizing treatment, and the time is 20 minutes. The CNO ^- concentration in the salt bath is controlled at about 32%.

Step 4: Salt bath oxidation: put the broach after salt bath nitriding treatment in a 350°C oxidation salt bath furnace for 20 minutes, take it out of the furnace and cool to room temperature. Wash with water for 5 minutes to remove the salt on the surface.

Step 5: Polishing: Polish the surface of the broach to remove the loose layer on the surface.

Step 6: Repeat the above steps 3, 4, and 5 to perform surface toughening treatment twice to increase the depth of the seepage layer.

Example 4

The strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel spline broach with a size of Φ30×900mm is as follows:

Step 1, graded quenching: Preheat the high-speed steel broach in an air furnace at 500°C for 2 hours at low temperature; preheat it in a salt bath furnace at 870°C for 10 minutes at medium temperature; heat it in a high temperature salt bath furnace to 1220°C for 5 minutes; then Quenching in stages in a salt bath at a temperature of 550°C for 5 minutes.

Step 2, high-temperature tempering: temper the quenched high-speed steel broach in a 560°C salt bath furnace for 1 hour, then air-cool to room temperature, and perform 2 tempering according to this process.

Step 3, salt bath nitriding: the high-speed steel broach obtained in step 2 is subjected to salt-bath carbonitriding treatment, the method is as follows: (1) cleaning: the high-speed steel broach is cleaned with water to remove the salt on the surface; (2 ) Preheating: the preheating temperature is 400°C, and the time is 20 minutes; (3) Nitriding treatment: the broach is immersed in a salt bath furnace at 540°C for nitrocarburizing treatment, and the time is 25 minutes. The CNO ^- concentration in the salt bath is controlled at about 32%.

Step 4. Salt bath oxidation: put the broach after salt bath nitriding treatment in a 380°C oxidation salt bath furnace for 20 minutes, take it out of the furnace and cool to room temperature. Wash with water for 5 minutes to remove the salt on the surface.

Step 5. Polishing: Polish the surface of the broach to remove the loose layer on the surface.

Step 6. Repeat the above steps 3, 4 and 5 for 2 times.

XRD pattern analysis of W6Mo5Cr4V2 high-speed steel treated with surface strengthening treatment in Experimental Example 4

The phase composition analysis was carried out on the surface of the W6Mo5Cr4V2 high-speed steel surface provided by the surface strengthening treatment provided in Examples 1-3, and the results are shown in FIG. 1 . Studies have shown that after low-temperature salt-bath nitriding and salt-bath oxidation treatment, the surface of high-speed steel forms a Fe ₃ O ₄ oxide layer and a diffusion layer in which nitrogen and carbon are dissolved in α-Fe, and no compound layer is seen, effectively improving It improves the hardness of the surface while maintaining the toughness of the broach core.

Experimental Example 5 Cross-sectional gradient hardness test of W6Mo5Cr4V2 high-speed steel with surface strengthening treatment

A microhardness tester (HVS-1000) was used to test the gradient hardness of the W6Mo5Cr4V2 high-speed steel section, and the results are shown in Figure 2. Experiments have proved that due to the infiltration of C and N atoms into the high-speed steel matrix, the surface hardness of high-speed steel increases significantly, and the hardness presents a gradient change from the surface to the inside, gradually decreasing to the hardness of the high-speed steel matrix (about 950Hv _0.1 ). Among them, the gradient hardness value of Example 2 is the highest, the surface hardness reaches above 1420Hv _0.1 , and the penetration layer depth exceeds 70 μm.

In summary, the present invention provides a method for strengthening and toughening the W6Mo5Cr4V2 high-speed steel broach. The high-speed steel broach has undergone several salt bath nitriding treatments, and the depth of the infiltrated layer is significantly increased, effectively improving the surface hardness of the broach, while The toughness of the broach core remains unchanged.

Claims (6)

1. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches, it is characterised in that include the following steps：

Step 1: grade quench, obtains quenched high-speed steel broach；

Step 2: high tempering：Quenched high-speed steel broach is tempered in salt bath furnace, is then air-cooled to room temperature, by this work Skill carries out 2 tempering, obtains the high-speed steel broach after high tempering；

Step 3: salt-bath nitriding：High-speed steel broach after high tempering is subjected to salt bath carbo-nitriding processing；

Step 4: liquid oxidizing：High-speed steel broach after salt bath nitriding treatment is put into oxidation salt bath furnace, comes out of the stove and is cooled to room Temperature removes the salt on surface through water cleaning；

Step 5: polishing：The high-speed steel broach surface that step 4 obtains is polished, surface porosity layer is removed.

Step 6: repeat the above steps three, four, five progress n times, wherein n >=1, improve depth of penetration, obtain the tough height of table hard-core Fast steel broaching tool.

2. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches according to claim 1, it is characterised in that： In step 1, grade quench be first by high-speed steel broach in 400~550 DEG C of air furnaces 2~4h of low-temperature prewarming, then exist Medium temperature preheats 10~20min in 850~870 DEG C of salt bath furnaces；Then be heated in High Temperature Salt Bath Furnace hardening heat 1200~ 1220 DEG C, 10~18s/mm of soaking time；Then the grade quench in salt bath, 500~550 DEG C, 10~18s/mm of time of temperature, Obtain quenched high-speed steel broach.

3. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches according to claim 1, it is characterised in that： In step 3, steps are as follows for salt-bath nitriding：

1) it cleans：High-speed steel broach is carried out to the salt on cleaning removal surface with water；

2) it preheats：Preheating temperature is 350~400 DEG C, and the time is 20~30min.It is in high-speed steel broach surface shape to preheat purpose At very thin FeO films, promote subsequent nitriding；

3) nitrogen treatment：High-speed steel broach is immersed in 540~550 DEG C of salt bath furnace and carries out nitrocarburizing processing, time 20 ~40min.

4. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches according to claim 3, it is characterised in that： CNO in the salt bath furnace^-A concentration of 30~32%.

5. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches according to claim 1, it is characterised in that： In step 4, the high-speed steel broach after salt bath nitriding treatment is put into 20~30min in 380~400 DEG C of oxidation salt bath furnaces.

6. a kind of strengthening and toughening treatment method of W6Mo5Cr4V2 high-speed steel broaches according to claim 1, it is characterised in that： In step 6, repeat the above steps three, four, five progress 2 times, improves depth of penetration.