A method for processing a powder metallurgy high-alloy high-speed steel wire

Abstract

The application discloses a processing method of powder metallurgy high-alloy high-speed steel wire rod, which comprises the following steps: (1) heating the powder metallurgy high-speed steel rod to 300-600 DEG C for pre-drawing; (2) heating the pre-drawn powder metallurgy steel wire to 850-900 DEG C first, and then cooling to 720-780 DEG C for isothermal treatment to perform microstructure grading and refining treatment; (3) performing small-strain single-pass cold drawing on the refined steel wire, and the strain is controlled to be below 0.2; (4) heating the drawn steel wire to 400-550 DEG C for activation treatment; and (5) heating the activated steel wire to 720-820 DEG C for equiaxed fine-grain treatment, and then water cooling to room temperature. The method can refine the microstructure of the powder metallurgy high-alloy high-speed steel wire rod, improve the dispersion degree of secondary carbides in the microstructure of the wire rod, and thus improve the processing plasticity of the wire rod.

Description

Technical Field

[0001] This invention relates to a method for processing powder metallurgy high-alloy high-speed steel wire. Background Technology

[0002] High-speed steel is widely used in the manufacture of various high-efficiency and precision tools such as milling cutters, gear planers, turning tools, twist drills, and bimetallic saw blades, and is an important basic material for the equipment manufacturing industry. High-speed steel tools are mostly made from high-speed steel wire, and the manufacturing process is as follows: smelting → refining → casting → electroslag remelting → forging → rolling → cold drawing / cold rolling → intermediate annealing → wire → finished product annealing. However, high-speed steel produced by the above casting and forging process is prone to problems such as coarse carbides, uneven distribution, and banded segregation, which cannot meet the stringent microstructure requirements of high-end cutting tools.

[0003] Powder metallurgy utilizes the atomization of alloy droplets to achieve extremely rapid cooling, which can suppress elemental segregation. This overcomes the problems of severe microstructure segregation and the inability to further increase alloying in traditional cast and forged high-speed steel, making it an advanced process for manufacturing high-end high-speed steel cutting tools. However, existing processing methods for powder metallurgy high-alloy high-speed steel wires have the following problems: the resulting wire microstructure contains a large number of carbide particles, mainly micron-sized primary carbides, with very few fine submicron-sized secondary carbides. This leads to deterioration of the wire's plasticity, making it prone to fracture during processing. Furthermore, it negatively impacts the performance of the final product, requiring higher quenching temperatures to ensure quenching hardness, resulting in grain coarsening and decreased toughness. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a processing method for powder metallurgy high-alloy high-speed steel wire. This method can increase the amount of secondary carbides in the microstructure of powder metallurgy high-alloy high-speed steel wire, refine the wire microstructure, and improve the wire plasticity, thereby facilitating subsequent processing.

[0005] Technical solution: The processing method for powder metallurgy high-alloy high-speed steel wire of the present invention includes the following steps:

[0006] (1) Powder metallurgy high-speed steel wire rod is pre-drawn by heating it to 300-600℃ using magnetic induction heating method;

[0007] (2) The pre-drawn powder metallurgy steel wire is first heated to 850-900℃ and then cooled to 720-780℃ isothermally to carry out microstructure classification and refinement treatment.

[0008] (3) The refined steel wire is cold-drawn with small strain, and the strain is controlled below 0.2;

[0009] (4) Heat the drawn steel wire to 400-550℃ for activation treatment;

[0010] (5) Heat the activated steel wire to 720-820°C for equiaxed fine crystallization treatment, and then cool it to room temperature with water.

[0011] In step (1), the heating method is electromagnetic induction heating. Magnetic induction heating is not only about temperature, but more importantly, it uses a magnetic field to induce the precipitation of carbides. Other heating methods do not have this condition at the same time.

[0012] In step (1), the pre-stretch strain is 0.1 to 0.3.

[0013] In step (2), the temperature is heated at 850-900℃ for 1-3 hours; and isothermal treatment at 720-780℃ for 4-8 hours.

[0014] In step (4), the activation treatment time is 30 min to 2 h.

[0015] In step (5), the equiaxed fine crystallization treatment time is 10 min to 1 h.

[0016] Among them, repeating steps (3) to (5) at least twice enhances the above-mentioned organizational control effect.

[0017] Invention Principle: This invention involves electromagnetic thermal drawing of powder metallurgy high-speed steel wire rods at a temperature range of 300–600°C. Electromagnetic thermal induction induces the precipitation of ferromagnetic Fe3W3C (M6C) carbides, providing nucleation sites for the subsequent staged heat treatment to induce the precipitation of submicron-sized secondary carbides. Through staged heat treatment—first heating the pre-drawn steel wire to 850–900°C, then cooling it isothermally to 720–780°C—the electromagnetically induced carbides serve as the core, inducing the precipitation of a large number of submicron-sized secondary carbides, refining the steel wire microstructure, and improving the room temperature drawing plasticity of the steel wire. The invention also involves small-scale stress treatment of the steel wire. The single-pass cold drawing process allows some carbon and alloying elements to dissolve back. Activation treatment at 400–550°C increases the carbon atom concentration at the drawing defects, activating a large number of fine carbide nucleation sites, laying the foundation for the re-precipitation of carbides after equiaxed fine grain treatment. Finally, the steel wire undergoes equiaxed fine grain treatment at 720–820°C to form an equiaxed fine grain structure, precipitating submicron-sized carbides. Subsequent water cooling treatment suppresses the precipitation of tertiary carbides that are detrimental to the plasticity of the steel wire. Repeating steps (3) to (5) three or more times can further enhance the above-mentioned microstructure control effect.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The method of the present invention can refine the microstructure of powder metallurgy high alloy high-speed steel wire, improve the dispersion of secondary carbides in the wire microstructure, thereby improving the processing plasticity of the wire, and enable the wire to achieve high hardness even with reduced quenching temperature and time during subsequent high-temperature quenching processing into cutting tools, thereby refining the grain size after quenching, so that the cutting tool has both good toughness and high hardness. Attached Figure Description

[0019] Figure 1 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Example 1;

[0020] Figure 2 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Example 2;

[0021] Figure 3 Here is a SEM image of the microstructure of the powder metallurgy 558 high-speed steel wire obtained in Example 3;

[0022] Figure 4 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Comparative Example 1;

[0023] Figure 5 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Comparative Example 2;

[0024] Figure 6 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Comparative Example 3;

[0025] Figure 7 SEM image of the microstructure of powder metallurgy 558 high-speed steel wire obtained in Comparative Example 4;

[0026] Figure 8 The image shows the SEM image of the microstructure of the powder metallurgy 558 high-speed steel wire obtained in Comparative Example 5. Detailed Implementation

[0027] Example 1

[0028] The present invention relates to a method for processing powder metallurgy 558 high-speed steel wire, comprising the following steps:

[0029] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 300℃, with a strain of 0.1;

[0030] (2) The pre-drawn powder metallurgy steel wire is first heated to 850℃ and kept at that temperature for 3 hours, and then cooled to 720℃ and isothermal for 8 hours to carry out microstructure classification and refinement treatment.

[0031] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.1;

[0032] (4) Heat the drawn steel wire to 400℃ for activation treatment and keep it at that temperature for 2 hours;

[0033] (5) Heat the activated steel wire to 720℃ and isothermal for 1 hour, then cool it to room temperature with water;

[0034] (6) Repeat steps (3) to (5) twice.

[0035] from Figure 1 It can be seen that the powder metallurgy 558 steel wire has a fine microstructure, with a secondary carbide number density of 3.9 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 11.7%. After quenching at 1220℃ and tempering at 560℃ (quenching: first stage: heat up to 850℃ for 60 minutes and hold for 40 minutes; second stage: heat up to 1050℃ for 30 minutes and hold for 40 minutes; third stage: heat up to 1200℃~1220℃ for 35 minutes and hold for 30 minutes; fourth stage: cool with 8000mbar (8 kg pressure) nitrogen for 20 minutes to 30℃; tempering: heat up to 560℃ for 30 minutes, hold at 560℃ for 2 hours, air cool to room temperature, repeat 3 times), the grain size is rated as level 11 according to JB / T9986 (the larger the level number, the smaller the grain size), and the hardness is 68HRC.

[0036] Example 2

[0037] The present invention relates to a method for processing powder metallurgy 558 high-speed steel wire, comprising the following steps:

[0038] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 600℃, with a strain of 0.3;

[0039] (2) The pre-drawn powder metallurgy steel wire is first heated to 900℃ and kept at that temperature for 1 hour, and then cooled to 780℃ and isothermal for 4 hours to carry out microstructure classification and refinement treatment.

[0040] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.15;

[0041] (4) Heat the drawn steel wire to 550℃ for activation treatment and hold for 30 minutes;

[0042] (5) Heat the activated steel wire to 820℃ and hold it at that temperature for 10 minutes, then cool it to room temperature with water;

[0043] (6) Repeat steps (3) to (5) three times.

[0044] from Figure 2 It can be seen that the powder metallurgy 558 steel wire has a fine microstructure, with a secondary carbide number density reaching 4.8 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 13.8%, and the grain size after quenching at 1220℃ and tempering at 560℃ is grade 11.5, with a hardness of 68.3 HRC.

[0045] Example 3

[0046] The present invention relates to a method for processing powder metallurgy 558 high-speed steel wire, comprising the following steps:

[0047] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 500℃, with a strain of 0.2;

[0048] (2) The pre-drawn powder metallurgy steel wire is first heated to 880℃ and isothermaled for 2 hours, and then cooled to 760℃ and isothermaled for 6 hours to carry out the microstructure classification and refinement treatment.

[0049] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.2;

[0050] (4) Heat the drawn steel wire to 500℃ for activation treatment and keep it at that temperature for 1 hour;

[0051] (5) Heat the activated steel wire to 780℃ and isothermal for 30 minutes, then cool it to room temperature with water;

[0052] (6) Repeat steps (3) to (5) four times.

[0053] from Figure 3 It can be seen that the powder metallurgy 558 steel wire has a fine microstructure, with a secondary carbide number density reaching 4.3 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 12.3%, and the grain size after quenching at 1220℃ and tempering at 560℃ is grade 11, with a hardness of 68.2 HRC.

[0054] Comparative Example 1

[0055] A method for processing powder metallurgy 558 high-speed steel wire includes the following steps:

[0056] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 200℃, with a strain of 0.1;

[0057] (2) The pre-drawn powder metallurgy steel wire is first heated to 850℃ and kept at that temperature for 3 hours, and then cooled to 720℃ and isothermal for 8 hours to carry out microstructure classification and refinement treatment.

[0058] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.1;

[0059] (4) Heat the drawn steel wire to 400℃ for activation treatment and keep it at that temperature for 2 hours;

[0060] (5) Heat the activated steel wire to 720℃ and isothermal for 1 hour, then cool it to room temperature with water;

[0061] (6) Repeat steps (3) to (5) twice.

[0062] from Figure 4 It can be seen that the powder metallurgy 558 steel wire has fewer secondary carbides, with a number density of 1.6 × 10⁻⁶. 6 pcs / cm 2 The total elongation was 7.5%, and after quenching at 1220℃ and tempering at 560℃, the grain size was grade 10.5 and the hardness was 67.3 HRC. Under the same heat treatment process as Example 1, the material obtained in Comparative Example 1 had a large grain size and low hardness. To achieve the same hardness as in Example 1, it is necessary to increase the heat treatment temperature and time of the wire.

[0063] Comparative Example 2

[0064] A method for processing powder metallurgy 558 high-speed steel wire includes the following steps:

[0065] (1) The powder metallurgy high-speed steel wire rod is pre-drawn by heating it to 300°C using electric heating, with a strain of 0.1.

[0066] (2) The pre-drawn powder metallurgy steel wire is first heated to 850℃ and kept at that temperature for 3 hours, and then cooled to 720℃ and isothermal for 8 hours to carry out microstructure classification and refinement treatment.

[0067] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.1;

[0068] (4) Heat the drawn steel wire to 400℃ for activation treatment and keep it at that temperature for 2 hours;

[0069] (5) Heat the activated steel wire to 720℃ and isothermal for 1 hour, then cool it to room temperature with water;

[0070] (6) Repeat steps (3) to (5) twice.

[0071] from Figure 5 It can be seen that the powder metallurgy 558 steel wire has fewer secondary carbides, with a number density of 1.2 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 8%, and the grain size is grade 10 after quenching at 1220℃ and tempering at 560℃. The hardness is 67HRC.

[0072] Comparative Example 3

[0073] A method for processing powder metallurgy 558 high-speed steel wire includes the following steps:

[0074] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 600℃, with a strain of 0.3;

[0075] (2) The pre-drawn powder metallurgy steel wire is first heated to 950℃ and kept at that temperature for 1 hour, and then cooled to 700℃ and isothermal for 4 hours to carry out microstructure classification and refinement treatment.

[0076] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.15;

[0077] (4) Heat the drawn steel wire to 550℃ for activation treatment and hold for 30 minutes;

[0078] (5) Heat the activated steel wire to 820℃ and hold it at that temperature for 10 minutes, then cool it to room temperature with water;

[0079] (6) Repeat steps (3) to (5) three times.

[0080] from Figure 6 It can be seen that the powder metallurgy 558 steel wire has fewer secondary carbides, with a number density of 1.3 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 7.2%, and the grain size after quenching at 1220℃ and tempering at 560℃ is grade 10, with a hardness of 67.4 HRC.

[0081] Comparative Example 4

[0082] A method for processing powder metallurgy 558 high-speed steel wire includes the following steps:

[0083] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 500℃, with a strain of 0.2;

[0084] (2) The pre-drawn powder metallurgy steel wire is first heated to 880℃ and isothermaled for 2 hours, and then cooled to 760℃ and isothermaled for 6 hours to carry out the microstructure classification and refinement treatment.

[0085] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.2;

[0086] (4) Heat the drawn steel wire to 300℃ for activation treatment and keep it at that temperature for 2 hours;

[0087] (5) Heat the activated steel wire to 780℃ and isothermal for 30 minutes, then cool it to room temperature with water;

[0088] (6) Repeat steps (3) to (5) four times.

[0089] from Figure 7 It can be seen that the powder metallurgy 558 steel wire has fewer secondary carbides, with a number density of 1.5 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 7.8%, and the grain size after quenching at 1220℃ and tempering at 560℃ is grade 10, with a hardness of 67HRC.

[0090] Comparative Example 5

[0091] A method for processing powder metallurgy 558 high-speed steel wire includes the following steps:

[0092] (1) Pre-drawing of powder metallurgy high-speed steel wire rod by magnetic induction heating to 300℃, with a strain of 0.1;

[0093] (2) The pre-drawn powder metallurgy steel wire is first heated to 850℃ and kept at that temperature for 3 hours, and then cooled to 720℃ and isothermal for 8 hours to carry out microstructure classification and refinement treatment.

[0094] (3) The refined steel wire is cold-drawn with a small strain, and the strain per pass is 0.1;

[0095] (4) Heat the drawn steel wire to 400℃ for activation treatment and keep it at that temperature for 2 hours;

[0096] (5) Heat the activated steel wire to 700℃ and isothermal for 1 hour, then furnace cool to room temperature;

[0097] (6) Repeat steps (3) to (5) twice.

[0098] from Figure 8 It can be seen that the secondary carbides in the powder metallurgy 558 steel wire are scarce, with a number density of 1.0 × 10⁻⁶. 6 pcs / cm 2 The total elongation is 6.9%, and the grain size after quenching at 1220℃ and tempering at 560℃ is grade 10.5, with a hardness of 67.1 HRC.

Claims

1. A method for processing powder metallurgy high-alloy high-speed steel wire, characterized in that, Includes the following steps: (1) Pre-draw the powder metallurgy high-speed steel wire rod to 300~600℃; the heating method is electromagnetic induction heating. (2) The pre-drawn powder metallurgy steel wire is first heated to 850~900℃, and then cooled to 720~780℃ isothermally to carry out microstructure classification and refinement treatment; (3) The refined steel wire is subjected to small strain single-pass cold drawing, and the strain is controlled below 0.2; (4) Heat the drawn steel wire to 400-550℃ for activation treatment; (5) The activated steel wire is heated to 720-820°C and subjected to equiaxed fine graining treatment, and then cooled to room temperature to obtain high-speed steel wire; the high-speed steel wire is 558 high-speed steel wire.

2. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: In step (1), the pre-stretch strain is 0.1~0.

3.

3. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: In step (2), heat at 850~900℃ for 1~3 hours.

4. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: In step (2), the isothermal treatment at 720~780℃ takes 4~8 hours.

5. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: In step (4), the activation treatment time is 30 min to 2 h.

6. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: In step (5), the equiaxed fine crystallization treatment time is 10 min to 1 h.

7. The processing method for powder metallurgy high-alloy high-speed steel wire according to claim 1, characterized in that: Repeat steps (3) to (5) at least twice.

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