CN111850391A

CN111850391A - High-speed steel for screw punch and preparation method thereof

Info

Publication number: CN111850391A
Application number: CN202010557632.3A
Authority: CN
Inventors: 李栋
Original assignee: HEYE SPECIAL STEEL CO LTD
Current assignee: HEYE SPECIAL STEEL CO LTD
Priority date: 2020-06-18
Filing date: 2020-06-18
Publication date: 2020-10-30
Anticipated expiration: 2040-06-18
Also published as: CN111850391B

Abstract

The invention discloses high-speed steel for a screw punch and a preparation method thereof, wherein the high-speed steel comprises the following chemical components in percentage by mass: c1.00-1.07%, 0.20-0.40% of Si, 0.20-0.40% of Mn, up to 0.025% of P, up to 0.010% of S, 3.80-4.20% of Cr, 5.50-5.90% of Mo, 5.50-5.90% of W, 2.20-2.50% of V, 4.50-6.20% of Co, less than or equal to 0.005% of N, less than or equal to 0.016% of Ti, 0.16-0.20% of Al, 0.08-0.10% of RE, and the balance of iron and inevitable impurities. The invention can easily obtain high-hardness and high-toughness structure, MC and M in steel₆C, fine particles; the high-speed steel of the invention is subjected to high-temperature spheroidizing annealing and vacuum furnace stress relief annealing, thus ensuring low annealing hardness, high surface shrinkage and good plasticity of later metal processing.

Description

High-speed steel for screw punch and preparation method thereof

Technical Field

The invention relates to the technical field of high-speed steel production, in particular to high-speed steel for a screw punch and a preparation method thereof.

Background

With the rapid development of the mechanical industry, the automation and high efficiency of equipment and equipment used for manufacturing standard parts are higher and higher, a cold heading machine for screw products is developed into a multi-station cold heading machine and has the functions of one-step punching and two-step die, the working principle of the cold heading machine is wire straightening, wire feeding, shearing, feeding into a main die, one-step punching and initial forging, two-step punching and blank withdrawing, the forming effect of the head of a screw is mainly performed, after multi-station combination, the processes of trimming are reduced, and then a screw punch of the one-step punching and the two-step punching is required to have higher strength and toughness in the high-speed (more than or equal to 400 times/minute) cold heading process, the screw punch is guaranteed not to collapse and deform in the cold heading process, and the head of the screw is guaranteed not to be subjected.

With the rapid development of the automobile and aviation industries in China, the requirements for high-strength screws are correspondingly improved, the performance of the screws is developed from 8.9 grade to 12.9 grade, and the preparation raw materials of the screws are also developed from common steel to stainless steel and alloy steel, so that the hardness and the heat strength of the punch are required to be higher and higher. At present, screw punches made of materials such as W6Mo5Cr4V2 and W2Mo9Cr4V2 commonly used in the market cannot meet the production requirements, a large amount of screw punch materials (more than 6000 tons) need to be imported every year, and the screw punch materials need to be upgraded urgently.

Disclosure of Invention

In order to meet the requirement of upgrading the screw punch and the requirements of high strength, high toughness and high red hardness of the screw punch, the invention provides a screw punch material and a preparation process of the material, so that smaller carbide particles and excellent red hardness, high strength and high toughness can be obtained.

In order to achieve the purpose, the invention provides the following technical scheme:

the high-speed steel for the screw punch comprises the following chemical components in percentage by mass: 1.00 to 1.07 percent of C, 0.20 to 0.40 percent of Si, 0.20 to 0.40 percent of Mn, 0.025 percent of P at most, 0.010 percent of S at most, 3.80 to 4.20 percent of Cr, 5.50 to 5.90 percent of Mo, 5.50 to 5.90 percent of W, 2.20 to 2.50 percent of V, 4.50 to 6.20 percent of Co, less than or equal to 0.005 percent of N, less than or equal to 0.016 percent of Ti, 0.16 to 0.20 percent of Al,0.08 to 0.10 percent of RE and the balance of iron and inevitable impurities.

The invention balances the contents of W and Mo, adds Re element for inoculation, adds Co element to improve the multi-element composite design principle of thermal stability, and comprehensively considers the mechanism of precipitation and growth of carbides of different elements in the solidification process to prepare the high-strength high-toughness high-red hard alloy by adopting a special process, so that the high-strength high-toughness high-red hard alloy has excellent high strength, high toughness and red hard property.

C is one of the carbide components, and part of the C is dissolved in the matrix to improve the matrix strength. The content of the C element is not higher than 1.07 percent, so that the fact that ledeburite structures are not generated or are generated less in the process of solidifying the molten steel is ensured, and the control of the quantity of MC carbides and the carbide segregation is facilitated; the content of C element is not less than 1.00% to ensure the proper hardness after heat treatment.

The W element is a carbide-forming element and forms M with the carbon element₆C carbide, which prevents the growth of crystal grains and improves the high-temperature hardness and the wear resistance of the steel. The content of W element is not higher than 5.90%. So as to ensure that the molten steel generates less M in the solidification process₆C skeleton-shaped ledeburite structure prevents the plastic property of the steel from being influenced by difficult breakage of later-stage hot working; the W element is not less than 5.50% to ensure the formation of enough carbide and improve the wear resistance and red hardness of the steel.

Mo element is a carbide forming element, and under the condition of non-equilibrium cooling, the carbide formed by the Mo element is subjected to phase change to generate M in a metastable state₂C carbide, sheet-like and sector-shaped M2C, cooling after solidification, forging, heating, and decomposing into fine M₆C + MC, and makes it easy to distribute uniformly, increases the toughness of the steel and improves the thermoplasticity of the steel. The stability of carbide and the strength and wear resistance of the steel are improved. The Mo element of the invention is controlled to be 5.50-5.90%.

The equivalent relationship between W element and Mo element to form carbide with C is 1.0% W equivalent to 1.8% Mo, W and Mo can be substituted for each other, and the invention controls W equivalent [ W ] -W + Mo/1.8, 8.55. ltoreq. W.ltoreq.9.18.

Function of Cr element: the Cr element can promote the precipitation of carbide, and meanwhile, part of the Cr element is dissolved in the matrix in a solid mode and mainly acts on improving the hardenability and the tempering hardness of the steel. The content of Cr element in the invention is 3.80-4.20%.

The element V is a strong carbide forming element and forms pre-eutectic and eutectic MC in the solidification process. The content of V is increased, the larger the difference value between the precipitation temperature of the pre-eutectic MC and the precipitation temperature of the eutectic MC is, the larger the pre-eutectic MC particles are. Considering the quenching hardness and the MC granularity of steel comprehensively, the method determines the V: 2.20-2.50%.

The N element acts, the bonding capacity of the N element and the V element in the steel is stronger than that of C, the N element partially replaces C atoms in MC to form M (CN) type carbonitride, the melting of nitrogen increases the precipitation temperature of pre-eutectic carbide, the delta T value is increased, and the size of primary carbide of MC is increased. In order to reduce the size of MC carbide particles, the invention requires that N is less than or equal to 0.005 percent.

Under the action of Ti element, the binding capacity of Ti element and C element of steel grade is stronger than that of V element, and during the solidification process, eutectic MC carbide can be coarsened to grow MC particles. The invention requires Ti to be less than or equal to 0.016 percent for reducing the grain size of MC carbide.

The Al element refines the as-cast structure, so that the dendrite spacing is reduced, the carbide is refined, and the carbide is distributed more uniformly and has smaller size. Meanwhile, Al generates interface action on diffusion of other elements, and when the content is higher, a ferrite structure is easy to appear in a quenching structure, and the invention requires 0.16-0.20% of Al for reducing the size of carbide.

RE element makes the impurities in the steel deformed in different degrees, and the irregular string distribution is changed into spherical dispersion distribution and fine distribution; the addition of rare earth effectively improves the anisotropy and low-temperature brittleness of the steel. And the ratio of the lateral impact value to the lateral longitudinal impact value increases as the RE/S increases. Meanwhile, as seen from the impact fracture, the fracture with the rare earth has obvious necking compared with the fracture without the rare earth, and no delamination crack appears in the fracture basically.

After rare earth elements are added into steel, the segregation of inclusions is improved, and a brittle zone in the steel disappears, so that fracture delamination is obviously improved, and the transverse toughness, namely anisotropy, of the steel is obviously improved. After rare earth is added into steel, the liquid-solid phase line temperature of molten steel is reduced due to the enrichment effect of the rare earth at the front of crystallization, and the superheat degree of the molten steel during crystallization is reduced, so that the isometric crystal rate is increased by 10-15%, namely the original crystal grain size is increased; on the other hand, since the rare earth element is a surface active material, the solid-solution rare earth is mainly distributed in the grain boundary, thereby reducing the interfacial tension and the interfacial energy, namely, the austenite grain growth is greatly moved to a higher temperature range, and the austenite grain growth is greatly inhibited. In the invention, Re is controlled to be 0.08-0.10%.

Si element strengthens ferrite, enhances the secondary hardening capacity of steel heat treatment, reduces the critical cooling speed of steel and improves the hardenability of steel. The Si content of the invention is controlled between 0.20 and 0.40 percent.

Mn element makes the cutting easy to break, and is beneficial to improving the quality of the processed surface. S is a metal inclusion forming element, in order to improve and eliminate the harm of S and Fe and other elements forming low-melting-point nonmetal inclusions, a proper amount of Mn and S is controlled to form MnS, but the MnS is distributed in an extending way in the rolling direction, so that the toughness in the rolling direction is reduced, the lower the S content is, the better the S content is, the invention requires that S is less than or equal to 0.010 percent, and Mn is controlled to be 0.20-0.40 percent.

Co element and iron form a continuous solid solution, and Co inhibits and delays the precipitation and aggregation of carbides of other elements in the using process, thereby obviously improving the heat strength and the high-temperature hardness of the steel. In the invention, Co is controlled to be 4.50-6.20%.

The invention also provides a method for preparing the material, which is used for preparing the material and comprises the following steps:

preparing a steel ingot:

scheme 1, melting alloy and return materials by a neutral crucible, pouring the alloy and the return materials into a steel ladle, refining outside an LF furnace, vacuum degassing and pouring into an electrode rod by a VD furnace, and then smelting into phi 215 electroslag ingots by electroslag remelting or continuous cooling ingot drawing type electroslag remelting.

And 2, melting the alloy and the return material by using a neutral crucible, pouring the molten alloy and the return material into a steel ladle, refining the molten alloy outside an LF furnace, and performing vacuum degassing and pouring by using a VD furnace to obtain an F435 cast ingot.

Scheme 3, melting the alloy and the return material by adopting a neutral crucible, pouring the molten alloy and the return material into a steel ladle, performing ESF (electron beam quenching) external refining, and performing spray forming to directly deposit the molten alloy and the return material into a steel ingot.

And annealing the steel ingot, heating the steel ingot by using an annular furnace, homogenizing the steel ingot at 1170-1180 ℃, and forging the steel ingot into a 125-square steel ingot after heating. After annealing the square billet by using waste heat at 760 ℃, rolling the square billet into phi 12-28 round steel by using a rolling mill, performing high-temperature spheroidizing annealing to straighten the lathe leather, and performing a specific vacuum stress relief annealing process. As a preparation material for screw punches.

Further, the electroslag ingot homogenization treatment comprises the following steps:

a first step: putting the electroslag ingot into a heating furnace, heating to 900 ℃ at the speed of 90-100 ℃/h, and preserving heat for 3 h; a second step: heating the electroslag ingot to 1070 ℃ at the speed of 90-100 ℃/h, and preserving the temperature for 1.5 h; a third step: heating the electroslag ingot to 1175 ℃ at the speed of 90-100 ℃/h, and preserving the temperature for 6.0 h; a fourth step: rapidly cooling the electroslag ingot to 900 ℃ at the speed of 200-; a fifth step: heating the electroslag ingot to 1125 ℃ at the speed of 100-.

Further, the spheroidizing annealing process comprises the following steps:

a first step: putting the steel into a heating furnace, heating to 630 ℃ at the speed of 90-100 ℃/h, and preserving heat for 2 h; a second step: heating the steel to 780 ℃ at the speed of 90-100 ℃/h, and preserving heat for 2.5 h; a third step: heating the steel to 880 ℃ at the speed of 90-100 ℃/h, and preserving heat for 5 h; the fourth step is to rapidly cool to 810 ℃ at the speed of more than or equal to 30 ℃/h; a fourth step: slowly reducing the temperature of the steel from 810 ℃ to 650 ℃ for 16 hours; a fifth step: and slowly reducing the temperature of the steel from 650 ℃ to 400 ℃ for 10 hours.

Further, the vacuum stress relief annealing comprises the following steps:

a first step: putting the steel into a heating furnace, heating to 780 ℃ at the speed of 90-100 ℃/h, and preserving heat for 5 h; a second step: heating the steel to 888 ℃ at the speed of 90-100 ℃/h, and keeping the temperature for 6 h; a third step: slowly reducing the temperature of the steel from 880 ℃ to 680 ℃ for 20 hours; a fourth step: and (3) preserving the heat of the steel at 680 ℃ for 3 hours, and taking the steel out of the furnace from 680 ℃ to 550 ℃ slowly for 5 hours in a fifth step.

Compared with the prior art, the invention has the following advantages:

(1) easily obtain high-hardness and high-toughness structure, MC in steelAnd M₆The C particles are fine.

(2) The high-temperature spheroidizing annealing and the stress relief annealing of the vacuum furnace ensure that the annealing hardness of steel is low, the surface shrinkage rate is high, the plasticity of later metal processing is good, and the yield of the back-flushing process in the screw punch preparation is high.

Detailed Description

The technical solution of the present patent will be described in further detail with reference to the following embodiments.

Example one

The embodiment relates to high-speed steel for a screw punch, which comprises the following components in percentage by mass: 1.03% of C, 0.30% of Si, 0.30% of Mn, 0.020% of P, 0.010% of S, 4.00% of Cr, 5.60% of Mo, 5.70% of W, 2.30% of V, 4.60% of Co, 0.0045% of N, 0.015% of Ti, 0.18% of Al, 0.08% of RE and the balance of iron and inevitable impurities.

The preparation method comprises the following steps:

s1, melting the alloy and the return material by a neutral crucible, pouring the molten alloy and the return material into a ladle, refining outside an LF furnace, vacuum degassing in a VD furnace, pouring into an electrode bar, and smelting into a phi 215 electroslag ingot through electroslag remelting.

The S2 steel ingot is annealed and then heated by a ring furnace, the heating temperature is 1170-1180 ℃ for homogenization, and the ingot is forged into a 125 square after heating.

Annealing the S3 square billet by 760 ℃ waste heat, rolling the square billet into phi 12-28 round steel by a rolling mill, spheroidizing and annealing the round steel at high temperature, straightening the wagon, and performing stress relief annealing by a vacuum furnace.

The S4 product is subject to 1190 ℃ oil quenching and 550 ℃ tempering, the hardness after tempering reaches 66HRC, the grain size reaches 11 grade, and the impact toughness is 38J.

Example two

The embodiment relates to high-speed steel for a screw punch, which comprises the following components in percentage by mass: 1.04% of C, 0.30% of Si, 0.30% of Mn, 0.020% of P, 0.010% of S, 4.10% of Cr, 5.80% of Mo, 5.80% of W, 2.40% of V, 5.00% of Co, 0.0045% of N, 0.015% of Ti, 0.18% of Al, 0.09% of RE and the balance of iron and inevitable impurities.

The preparation method comprises the following steps:

s1, melting the alloy and the return material by a neutral crucible, pouring the molten alloy and the return material into a ladle, refining the molten alloy outside an ESF furnace, and directly depositing the molten alloy and the return material into a steel ingot by spray forming.

The S4 product is subjected to 1190 ℃ oil quenching and 550 ℃ tempering, the hardness after tempering reaches 67HRC, the grain size reaches 11 grade, and the impact toughness is 37J.

Claims

1. The high-speed steel for the screw punch is characterized by comprising the following chemical components in percentage by mass: 1.00 to 1.07 percent of C, 0.20 to 0.40 percent of Si, 0.20 to 0.40 percent of Mn, 0.025 percent of P at most, 0.010 percent of S at most, 3.80 to 4.20 percent of Cr, 5.50 to 5.90 percent of Mo, 5.50 to 5.90 percent of W, 2.20 to 2.50 percent of V, 4.50 to 6.20 percent of Co, less than or equal to 0.005 percent of N, less than or equal to 0.016 percent of Ti, 0.16 to 0.20 percent of Al,0.08 to 0.10 percent of RE, and the balance of iron and inevitable impurities.

2. The high-speed steel for screw punches as claimed in claim 1, characterized in that the equivalent relationship of W element to Mo element to form carbide with C is 1.0% W corresponding to 1.8% Mo, W and Mo being replaceable with each other, the invention controlling W equivalent [ W ] -W + Mo/1.8, 8.55. ltoreq. W.ltoreq.9.18.

3. A preparation method of high-speed steel for a screw punch comprises the following steps:

Step one, steel ingot preparation:

scheme 1, melting alloy and return materials by using a neutral crucible, pouring the alloy and the return materials into a steel ladle, refining the alloy and the return materials outside an LF furnace, performing vacuum degassing and pouring the alloy and the return materials into an electrode bar by using a VD furnace, and performing electroslag remelting smelting or continuous cooling ingot drawing type electroslag remelting smelting to obtain a phi 215 electroslag ingot;

melting the alloy and the return material by using a neutral crucible, pouring the molten alloy and the return material into a steel ladle, refining the molten alloy outside an LF furnace, and performing vacuum degassing and pouring by using a VD furnace to obtain an F435 cast ingot;

scheme 3, melting the alloy and the return material by adopting a neutral crucible, pouring the molten alloy and the return material into a steel ladle, performing ESF (electron beam quenching) external refining, and performing injection molding to directly deposit the molten alloy and the return material into a steel ingot;

step two, annealing the steel ingot, heating the steel ingot in an annular furnace, homogenizing the steel ingot at 1170-1180 ℃, and forging the steel ingot into a square billet after heating;

step three, annealing the square billet by 760 ℃ waste heat, and rolling the square billet into round steel by a rolling mill;

step four, straightening and turning the round steel after high-temperature spheroidizing annealing;

and step five, performing a specific vacuum stress relief annealing process on the round steel treated in the step four to obtain the preparation material used as the screw punch.

4. The method for preparing high-speed steel for screw punches according to claim 3, characterized in that the electroslag ingot homogenization treatment comprises the following steps:

A first step: putting the electroslag ingot into a heating furnace, heating to 900 ℃ at the speed of 90-100 ℃/h, and preserving heat for 3 h;

a second step: heating the electroslag ingot to 1070 ℃ at the speed of 90-100 ℃/h, and preserving the temperature for 1.5 h;

a third step: heating the electroslag ingot to 1175 ℃ at the speed of 90-100 ℃/h, and preserving the temperature for 6.0 h;

a fourth step: rapidly cooling the electroslag ingot to 900 ℃ at the speed of 200-;

a fifth step: heating the electroslag ingot to 1125 ℃ at the speed of 100-.

5. The method for preparing the high-speed steel for the screw punch according to claim 3, wherein the spheroidizing annealing process comprises the following steps:

a first step: putting the steel into a heating furnace, heating to 630 ℃ at the speed of 90-100 ℃/h, and preserving heat for 2 h;

a second step: heating the steel to 780 ℃ at the speed of 90-100 ℃/h, and preserving heat for 2.5 h;

a third step: heating the steel to 880 ℃ at the speed of 90-100 ℃/h, and preserving heat for 5 h;

a fourth step: rapidly cooling to 810 ℃ at a speed of more than or equal to 30 ℃/h;

a fifth step: slowly reducing the temperature of the steel from 810 ℃ to 650 ℃ for 16 hours;

A sixth step: and slowly reducing the temperature of the steel from 650 ℃ to 400 ℃ for 10 hours.

6. The method for preparing high-speed steel for screw punches according to claim 3, characterized in that the vacuum stress relief annealing comprises the steps of:

a first step: putting the steel into a heating furnace, heating to 780 ℃ at the speed of 90-100 ℃/h, and preserving heat for 5 h;

a second step: heating the steel to 888 ℃ at the speed of 90-100 ℃/h, and keeping the temperature for 6 h;

a third step: slowly reducing the temperature of the steel from 880 ℃ to 680 ℃ for 20 hours;

a fourth step: keeping the temperature of the steel at 680 ℃ for 3 hours;

and a fifth step, slowly reducing the temperature of the steel from 680 ℃ to 550 ℃, discharging the steel for 5 hours.