CN113355584B - High-cobalt high-molybdenum superhard high-speed steel and method for improving hot working performance thereof - Google Patents

Abstract

The invention belongs to the technical field of high-speed steel, and particularly relates to high-cobalt high-molybdenum superhard high-speed steel and a method for improving the hot working performance of the high-cobalt high-molybdenum superhard high-speed steel. The improvement method provided by the invention comprises the following steps: carrying out induction smelting on industrial pure iron, a chromium-containing raw material, a molybdenum-containing raw material, metal tungsten, metal cobalt, graphite, industrial silicon, a manganese-containing raw material and a vanadium-containing raw material to obtain molten steel; carrying out pressurized electroslag remelting on the cast ingot obtained by casting the molten steel to obtain an electroslag ingot; the solidification pressure in the pressurized electroslag remelting process is 1-2 MPa; and sequentially carrying out high-temperature heat treatment and forging on the electroslag ingot to obtain the high-cobalt high-molybdenum superhard high-speed steel forging. By increasing the pressure of the pressurized electroslag remelting and solidification, the cooling rate of an electroslag ingot is increased, and eutectic carbide is refined; simultaneously, M in the electroslag ingot is treated by high-temperature heat treatment ₂ The C eutectic carbide is decomposed and spheroidized, the form and the size of the carbide are improved, and the hot workability and the processing yield of the high-cobalt high-molybdenum superhard high-speed steel are improved.

Description

A kind of high-cobalt and high-molybdenum superhard high-speed steel and method for improving its hot workability

technical field

The invention belongs to the technical field of high-speed steel, and particularly relates to a high-cobalt and high-molybdenum superhard type high-speed steel and a method for improving its hot workability.

Background technique

High-speed steel has the advantages of high hardness, good wear resistance, and excellent red hardness, and is widely used in cutting tools, high-load molds, aerospace high-temperature bearings, high-performance rolls and other fields. In recent years, with the rapid development of modern cutting technology, although high-speed steel faces the challenge of being replaced by cemented carbide and other materials, due to its good process performance, good strength and toughness, and strong impact resistance, it can be used to manufacture complex precision Cutting tools, impact and vibration-resistant cutting tools still occupy an important position in the field of tool materials, especially the demand for high-performance high-speed steel represented by M42 is still strong.

At present, the production process of high-speed steel is mainly based on the smelting process, that is, smelting → LF+VD refining → making electrode rods for electroslag remelting → forging. However, due to the high content of alloying elements (Co, Mo, W, Cr, V, etc.) and the limited cooling capacity of traditional electroslag remelting, high-speed steel is prone to serious segregation of carbon and alloying elements during the solidification process. Coarse network eutectic carbides are formed at the boundary. The existence of eutectic carbides will not only severely split the matrix, but also act as a source of cracks and a path for crack propagation, resulting in serious grain boundary embrittlement and reduction in thermoplasticity of high-speed steel, which in turn makes high-speed steel extremely easy to use in hot working processes such as forging and rolling. Cracking, low yield.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a high-cobalt and high-molybdenum superhard high-speed steel and a method for improving its hot workability. The invention improves the hot working performance of the high-cobalt and high-molybdenum superhard high-speed steel by increasing the solidification pressure during the remelting process of the pressurized slag, increasing the high-temperature heat treatment steps and optimizing the forging process, thereby improving the processing yield.

In order to solve the above-mentioned technical problems, the present invention provides a method for improving the hot workability of high-cobalt and high-molybdenum superhard type high-speed steel, comprising the following steps:

Smelting industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten, metal cobalt, graphite, industrial silicon, manganese-containing raw materials, and vanadium-containing raw materials to obtain molten steel;

The ingot obtained by casting the molten steel is subjected to pressurized electroslag remelting to obtain an electroslag ingot; the solidification pressure during the pressurized electroslag remelting process is 1-2 MPa;

The electroslag ingot is sequentially subjected to high temperature heat treatment and forging to obtain a high-cobalt and high-molybdenum superhard high-speed steel forging.

Preferably, the temperature of the high temperature heat treatment is 1100-1140°C, and the holding time is 6-10h; the heating rate to the temperature required for the heat treatment is 80-120°C/h.

Preferably, the voltage of the pressurized electroslag remelting is 33-40V, the current is 2200-3000A, and the pressure is 1-2MPa.

Preferably, the smelting comprises the following steps:

Induction melting of industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten and metal cobalt to obtain basic molten steel;

adding part of the graphite to the basic molten steel for vacuum carbon deoxidation to obtain pre-deoxidized molten steel;

The manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite are added to the pre-deoxidized molten steel for alloying to obtain molten steel.

Preferably, the temperature of the induction melting is 1480-1530°C;

Preferably, the vacuum degree of the vacuum carbon deoxidation is less than 30Pa, the time is 20-30min, and the temperature is 1430-1480°C.

Preferably, the alloying temperature is 1430-1480° C., and the time is 5-10 minutes.

Preferably, before the high temperature heat treatment, the method further comprises: coating the surface of the electroslag ingot with a coating; the coating comprises a binder and a powder, and the mass ratio of the binder and the powder is preferably 0.4-0.9:1;

The powder material includes the following components by mass percentage: 45-50% SiO ₂ , 22-26% Al ₂ O ₃ , 14-18% SiC, 2-4% CeO ₂ , 2-4% CaO, 5 ~8% white mud;

The binder is an aqueous sodium silicate solution with a density of 1.36-1.42 g/cm ³ .

Preferably, the start forging temperature of the forging is 1090-1120°C, and the final forging temperature is 960-980°C.

The present invention also provides the high-cobalt and high-molybdenum superhard type high-speed steel prepared by the preparation method described in the above technical solution, comprising the following chemical components by mass percentage: 0.9-1.2% C, 8-10% Mo, 7-9% Co , 3~5%Cr, 1~2.5%W, 0.7~1.5%V, 0.1~0.5%Si, 0.1~0.5%Mn, the balance is Fe and inevitable impurities.

The invention provides a method for improving the hot working performance of a high-cobalt and high-molybdenum superhard high-speed steel, comprising the following steps: mixing industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten, metal cobalt, graphite, industrial silicon, manganese-containing raw materials The raw materials and vanadium-containing raw materials are smelted to obtain molten steel; the ingot obtained by casting the molten steel is subjected to pressurized electroslag remelting to obtain an electroslag ingot; the solidification pressure during the pressurized electroslag remelting process is 1-2 MPa; The electroslag ingot is sequentially subjected to high temperature heat treatment and forging to obtain a high-cobalt and high-molybdenum superhard high-speed steel forging. The invention can effectively reduce the air gap between the ingot and the mold by increasing the solidification pressure during the remelting process of the pressurized electroslag, enhance the cooling effect of the mold, and improve the cooling rate of the electroslag ingot, thereby refining the solidification structure, Improve the distribution of eutectic carbides, thereby improving the hot workability of high cobalt and high molybdenum superhard high-speed steel. The invention decomposes the metastable M ₂ C eutectic carbide in the high cobalt and high molybdenum superhard type high-speed steel through high temperature heat treatment to generate M ₆ C and MC stable carbide; the decomposition and fracture of the M ₂ C eutectic carbide And spheroidization improves the continuity of the matrix and improves the shape and size of carbides, so it can effectively improve the hot workability of high-cobalt and high-molybdenum superhard high-speed steel, and improve its processing yield.

Description of drawings

Fig. 1 is the microstructure diagram after the high temperature heat treatment of the electroslag ingot prepared in Example 1;

Fig. 2 is the microstructure diagram after the high temperature heat treatment of the electroslag ingot prepared in Example 2;

Fig. 3 is the microstructure diagram of the high-cobalt and high-molybdenum superhard high-speed steel forging prepared in Example 1;

Fig. 4 is the microstructure diagram of the high-cobalt and high-molybdenum superhard high-speed steel forging prepared in Example 2;

Fig. 5 is the surface topography of the high-cobalt and high-molybdenum superhard high-speed steel forging prepared in Example 1;

Fig. 6 is the surface topography of the high-cobalt and high-molybdenum superhard high-speed steel forging prepared in Example 2;

FIG. 7 is the surface topography of the high-cobalt and high-molybdenum superhard high-speed steel forging prepared in Comparative Example 1.

Detailed ways

The invention provides a method for improving the hot workability of high-cobalt and high-molybdenum superhard high-speed steel, comprising the following steps:

Smelting industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten, metal cobalt, graphite, industrial silicon, manganese-containing raw materials, and vanadium-containing raw materials to obtain molten steel;

The ingot obtained by casting the molten steel is subjected to pressurized electroslag remelting to obtain an electroslag ingot; the solidification pressure during the pressurized electroslag remelting process is 1-2 MPa;

The electroslag ingot is sequentially subjected to high temperature heat treatment and forging to obtain a high-cobalt and high-molybdenum superhard high-speed steel forging.

The present invention smelts industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten, metal cobalt, graphite, industrial silicon, manganese-containing raw materials and vanadium-containing raw materials to obtain molten steel. In the present invention, the smelting preferably comprises the following steps:

Induction melting of industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten and metal cobalt to obtain basic molten steel;

adding part of the graphite to the basic molten steel for vacuum carbon deoxidation to obtain pre-deoxidized molten steel;

Manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite are added to the pre-deoxidized molten steel for alloying and casting to obtain an ingot.

In the present invention, industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten and metal cobalt are subjected to induction melting to obtain basic molten steel. In the present invention, the chromium-containing raw material preferably includes metallic chromium or ferrochromium, more preferably metallic chromium. In the present invention, the molybdenum-containing raw material preferably includes metallic molybdenum or ferromolybdenum, more preferably metallic molybdenum. The present invention has no special requirements on the mass ratio of the industrial pure iron, chromium-containing raw materials, molybdenum-containing raw materials, metal tungsten, and metal cobalt, and the ratio can be carried out according to the content of the chemical components of the required high-speed steel.

In the present invention, the induction melting is preferably vacuum induction melting; the vacuum degree of the vacuum induction melting is preferably below 10Pa, more preferably 5-8Pa; the temperature of the vacuum induction melting is preferably 1480-1530°C, more preferably Preferably it is 1500-1510 degreeC.

After the basic molten steel is obtained, the present invention adds part of the graphite into the basic molten steel for vacuum carbon deoxidation to obtain pre-deoxidized molten steel. In the present invention, the mass percentage content of the part of the graphite in the total mass of the graphite is preferably 40-80%, more preferably 50-60%. In the present invention, the mass ratio of the total mass of the graphite to the carbon in the ingot is preferably 1.03-1.08:1, more preferably 1.05-1.07:1. In the present invention, the graphite is used for deoxidation in addition to forming carbon in the target high-speed steel.

In the present invention, the process of adding part of the graphite to the basic molten steel is preferably carried out under a protective atmosphere, the protective atmosphere is preferably argon with a purity of ≥99.999%, and the pressure of the protective atmosphere is preferably 0.01-0.05MPa, more It is preferably 0.02 to 0.03 MPa. In the present invention, the vacuum carbon deoxidation is preferably performed under vacuum conditions, and the vacuum degree of the vacuum conditions is preferably less than 30Pa, more preferably 10-20Pa. In the present invention, the temperature of the vacuum carbon deoxidation is preferably 1430-1480°C, more preferably 1450-1470°C. In the present invention, the time for the vacuum carbon deoxidation is preferably 20-30 min, more preferably 20-25 min.

In the present invention, the vacuum carbon deoxidation can effectively reduce the oxygen content in the molten steel, help to improve the cleanliness of the electroslag ingot, and avoid oxygen elements from deteriorating the thermoplasticity of the high-cobalt and high-molybdenum superhard high-speed steel.

After obtaining the pre-deoxidized molten steel, the present invention adds manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite to the pre-deoxidized molten steel for alloying to obtain molten steel. In the present invention, the manganese-containing raw material preferably includes metallic manganese and electrolytic manganese, more preferably metallic manganese. In the present invention, the vanadium-containing raw material preferably includes metal vanadium or ferrovanadium, more preferably metal vanadium. The present invention has no special requirements on the mass ratio of the industrial silicon, manganese-containing raw materials, and vanadium-containing raw materials, and the ratio can be carried out according to the content of the chemical components of the required high-speed steel.

In the present invention, manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite are added to the pre-deoxidized molten steel, preferably manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite are sequentially added to the pre-deoxidized molten steel; The time interval for adding manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and remaining graphite is preferably 1 to 3 minutes, more preferably 2 minutes. The present invention preferably performs alloying during addition. In the present invention, the alloying process is preferably carried out under a protective atmosphere, the protective atmosphere is preferably argon with a purity of ≥99.999%, and the pressure of the protective atmosphere is preferably 0.01-0.03MPa, more preferably 0.02-0.03 MPa. In the present invention, the alloying temperature is preferably 1430 to 1480°C, more preferably 1450 to 1470°C.

In the present invention, the addition of manganese-containing raw materials, vanadium-containing raw materials, industrial silicon and residual graphite to the pre-deoxidized molten steel preferably also includes adding magnesium alloys and rare earths to perform deep deoxidation and deep desulfurization. In the present invention, the magnesium alloy preferably includes a nickel-magnesium alloy or an iron-magnesium alloy, more preferably a nickel-magnesium alloy. In the present invention, the mass percentage content of magnesium in the magnesium alloy is preferably 5-20%. In the present invention, the rare earth preferably includes cerium or lanthanum, more preferably cerium. In the present invention, based on one ton of high-cobalt and high-molybdenum superhard high-speed steel, the addition amount of magnesium in the magnesium alloy is preferably 0.006-0.012kg, more preferably 0.008-0.10kg; the addition amount of the rare earth is preferably 0.006-0.012kg. 0.3 to 0.6 kg, more preferably 0.4 to 0.5 kg.

By adding magnesium alloy and rare earth to molten steel, the invention can further reduce oxygen and sulfur impurities in molten steel, help improve the cleanliness of electroslag ingots, and avoid oxygen and sulfur impurity elements from deteriorating the high cobalt and high molybdenum superhard high-speed steel. Thermoplastic.

After the molten steel is obtained, the ingot obtained by casting the molten steel is subjected to pressurized electroslag remelting to obtain an electroslag ingot; the solidification pressure during the pressurized electroslag remelting process is 1-2 MPa.

In the present invention, the temperature of molten steel during casting is preferably 1430 to 1480°C, and more preferably 1450 to 1470°C. In the present invention, before the casting, the method further preferably includes: keeping the molten steel at the casting temperature. In the present invention, the incubation time is preferably 2-4 min, more preferably 3 min. The present invention has no special requirements for the casting, and a conventional method in the art can be used.

In the present invention, the pressurized electroslag remelting is preferably performed in a pressurized electroslag remelting furnace. In the present invention, the ingot is preferably forged to obtain a consumable electrode suitable for the size of the crystallizer of the pressurized slag remelting furnace. The present invention has no special limitation on the size of the consumable electrode, as long as it can adapt to the size of the crystallizer of the pressurized slag remelting furnace. In an embodiment of the present invention, the consumable electrode is a rod with a diameter of 80 mm. In the present invention, before the remelting of the pressurized slag, it is preferable to further include: welding the consumable electrode to the dummy electrode, and connecting the dummy electrode to the electrode holder; In the arc ignition ring at the center of the bottom water tank of the pressurized slag remelting furnace; after baking the pre-melted slag, add it into the crystallizer of the pressurized slag remelting furnace to start the arc and make slag.

Before welding the consumable electrode to the dummy electrode, the present invention preferably further comprises: polishing the surface of the consumable electrode. In the present invention, the present invention does not specifically limit the specific operation of the polishing, and the conventional polishing operation in the art may be used. In the invention, the surrounding area of the consumable electrode is polished to remove the oxide skin, which can prevent the increase of oxygen in the electroslag ingot.

In the present invention, the material of the arc ignition chips is preferably the same as that of the target high-speed steel. In the embodiment of the present invention, the amount of the arc ignition chips is preferably 0.25-0.35 kg, more preferably 0.28-0.32 kg. In the present invention, a gasket is preferably arranged between the arc ignition ring and the mold of the pressurized slag remelting furnace, and the material of the gasket is preferably cast iron. In the embodiment of the present invention, the diameter of the gasket is preferably 108-112 mm, more preferably 110 mm; the thickness of the gasket is preferably 8-12 mm, more preferably 10 mm. In the present invention, the consumable electrode, the arc ignition chips and the bottom water tank of the pressurized slag remelting furnace are in close contact, so as to ensure that the current passes after the power is turned on.

In the present invention, in terms of mass percentage, the pre-melted slag preferably includes 55-65% CaF ₂ , 15-25% CaO, 15-25% Al ₂ O ₃ and inevitable impurities; more preferably 58-62% CaF ₂ , 18-22% CaO, 18-22% Al ₂ O ₃ and inevitable impurities. In the present invention, the amount of the pre-melted slag is preferably 3-3.6 kg, more preferably 3.3-3.5 kg. In the present invention, the baking temperature is preferably 600-800°C, more preferably 650-750°C; the time is preferably 6-10 h, more preferably 8-9 h.

In the present invention, before the arc-forming slag-making process preferably further comprises: feeding argon gas into the pressurized electric slag remelting furnace. The purity of the argon is preferably ≥99.999%, the flow rate of the argon is preferably 10-20NL/min, more preferably 12-15NL/min, and the time is preferably 4-10min, more preferably 5-8min . The present invention removes the air in the pressurized electric slag remelting furnace by passing argon gas. In the present invention, the voltage for arcing and slagging is preferably 25-33V, more preferably 28-30V; the current is preferably 1200-2100A, more preferably 1600-2000A; the time is preferably 7-15min, more preferably 10 to 15 minutes.

In the present invention, the voltage of the pressurized slag remelting is preferably 33-40V, more preferably 35-40V; the current is preferably 2200-3000A, more preferably 2200-2500A. In the present invention, the fluctuation of the voltage and current is preferably less than 5%. In the present invention, the melting rate of the pressurized electroslag remelting is preferably determined according to formula 1:

v=(0.35～0.45)×D kg/h Formula 1;

Among them, D is the size of the crystallizer of the pressurized slag remelting furnace, and the unit is mm. In the embodiment of the present invention, the melting rate is specifically 50kg/h. In the present invention, the melting rate fluctuation is preferably less than 5%. In the present invention, the pressure of the pressurized electroslag remelting is preferably 1-2 MPa, more preferably 1.5-1.8 MPa. In the present invention, the pressure is preferably formed by passing argon gas into the melting chamber of the pressurized electric slag remelting furnace. In the present invention, the solidification pressure during the remelting process of the pressurized electric slag is 1-2 MPa, preferably 1.5-1.8 MPa, and the solidifying pressure refers to the gas pressure in the melting chamber. The present invention preferably fills the smelting chamber of the pressurized slag remelting furnace with argon gas, and simultaneously increases the cooling water pressure in the crystallizer jacket, so that the cooling water pressure is consistent with the pressure in the smelting chamber. In the present invention, the cooling method of the pressurized electric slag remelting is cooling water cooling.

In the present invention, after the remelting of the pressurized electroslag, the method further preferably includes: performing feeding and filling by gradually reducing the current; turning off the power supply, releasing the pressure, and taking out the electroslag ingot.

In the present invention, the method of gradually reducing the current is used to perform the feeding and filling. In the present invention, the method of reducing the current is preferably 500-1000A each time, more preferably 600-800A, to ensure sufficient feeding and filling, and ensure that the feeding end face is flat. In the present invention, the frequency of reducing the current is preferably 3 to 5 min/time, more preferably 4 min/time.

After the feeding and filling is completed, the present invention turns off the power supply, releases the pressure, and takes out the electroslag ingot. In the present invention, the pressure relief is preferably to reduce the pressure in the pressurized slag remelting furnace and the crystallizer, and the pressure after the pressure relief is normal pressure. In the present invention, after the electroslag ingot is taken out, the electroslag ingot is preferably placed in a heat preservation cover for slow cooling to prevent cracking.

After the electroslag ingot is obtained, the present invention sequentially performs high temperature heat treatment and forging on the electroslag ingot to obtain a high-cobalt and high-molybdenum superhard high-speed steel forging. In the present invention, before the high temperature heat treatment, the method further preferably includes: coating the surface of the electroslag ingot with paint. In the present invention, the coating preferably includes a binder and a powder. In the present invention, the binder is preferably an aqueous solution of sodium silicate (water glass), and the density of the binder is preferably 1.36-1.42 g/cm ³ . In the present invention, the powder preferably comprises the following components by mass percentage: 45-50% SiO ₂ , 22-26% Al ₂ O ₃ , 14-18% SiC, 2-4% CeO ₂ , 2 ～4% CaO, 5～8% white mud; in terms of mass percentage, the powder preferably comprises 45～50% SiO ₂ , more preferably 46～48%. In terms of mass percentage, the powder preferably comprises 22-26% Al ₂ O ₃ , more preferably 23-25%. In the present invention, low-melting sodium silicate is melted at high temperature to form a film to bond silicon dioxide and aluminum oxide to form a dense glassy coating film to protect the electroslag ingot at high temperature. In terms of mass percentage, the powder preferably comprises 14-18% SiC, more preferably 15-17%. In the present invention, the reaction of SiC and O ₂ reduces the oxygen potential around the coating and increases the protective effect of the coating at a low temperature stage. In terms of mass percentage, the powder preferably comprises 2-4% CeO ₂ , more preferably 2.5-3.5%. In the present invention, the ceria can improve the adhesion between the coating and the electroslag ingot, so that the coating can still be closely combined with the electroslag ingot at high temperature. In terms of mass percentage, the powder preferably comprises 2-4% CaO, more preferably 2.5-3.5%. In the present invention, the calcium oxide can improve the fluidity and lubricity of the coating at high temperature, so that the coating can evenly cover the surface of the electroslag ingot. In terms of mass percentage, the powder also preferably includes 5-8% white mud, more preferably 6-7%.

In the present invention, the average particle size of the powder is preferably 100-200 mesh, more preferably 100-150 mesh. In the present invention, the mass ratio of the binder and the powder is preferably 0.4-0.9:1, more preferably 0.5-0.7:1. In the present invention, the thickness of the coating layer after coating is preferably 0.3-0.6 mm, more preferably 0.4-0.5 mm.

In the present invention, the coating has good chemical stability, moderate surface tension, strong adhesion, good wettability and high temperature resistance. The invention can avoid serious oxidation and decarburization of the electroslag ingot by coating the surface of the electroslag ingot during the heat treatment process; meanwhile, the oxidation burning loss and the thickness of the decarburization layer of the electroslag ingot during the heat treatment process can be significantly reduced.

In the present invention, after the coating, the coating preferably further includes: drying the electroslag ingot coated with the coating. In the present invention, the drying temperature is preferably 20-50°C, more preferably 25-40°C; the time is preferably 8-15h, more preferably 9-12h.

In the present invention, the temperature of the high temperature heat treatment is preferably 1100-1140°C, more preferably 1120-1130°C; the holding time is preferably 6-10h, more preferably 6-8h. In the present invention, the heating rate to the temperature required for the heat treatment is preferably 80 to 120°C/h, more preferably 80 to 100°C/h. In the present invention, the initial temperature of the temperature rise is preferably less than 200°C, more preferably less than 150°C. In the present invention, the metastable M ₂ C eutectic carbide will undergo a decomposition reaction during the high temperature heat treatment to generate M ₆ C and MC stable carbides; the decomposition reaction is shown in formula 1:

M ₂ C+γ(Fe)→M ₆ C+MC Formula 1.

In the present invention, the forging further preferably includes: preheating the hammer and anvil; the temperature after the preheating is preferably 150-200°C. In the present invention, the forging starting temperature is preferably 1090-1120°C, more preferably 1100-1110°C; the final forging temperature is preferably 960-980°C, more preferably 970-980°C. In the present invention, when the temperature of the forging is above 1050°C, it is preferable to strike lightly to prevent the ingot from cracking; when the temperature of the forging is 980-1050°C, it is preferable to strike hard to ensure that the carbonization in the forging can be broken. thing. In the present invention, the number of times of the forging is preferably 3 to 5 times, and the total forging ratio of the forging is preferably 12 to 16.

The invention can reduce the cracking tendency of the electroslag ingot during the forging process by selecting different hitting degrees at different forging temperatures, and at the same time, the coarse eutectic carbides in the electroslag ingot can be broken, so as to obtain fine carbides with uniform distribution. organize. The invention performs forging under a large forging ratio, which can fully deform the high-speed steel, effectively break the as-cast structure, thereby reducing the size of carbides and making the carbides evenly distributed.

In the present invention, the forging also preferably includes: cooling the forged product, and the cooling rate of the cooling is preferably 80-120°C/h, more preferably 80-100°C/h. In the present invention, the cooling preferably includes cooling the forged product with the furnace in the heating furnace or covering the surface of the forged product with a heat-preserving material for cooling.

The present invention also provides that the high-speed steel prepared by the preparation method described in the above technical solution comprises the following chemical components by mass percentage:

In the present invention, the high-speed steel preferably includes the following chemical components by mass percentage:

In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present invention.

In the embodiment of the present invention, induction melting is carried out in a 50kg vacuum induction furnace, wherein the ultimate vacuum degree is 0.1Pa, and the furnace load is 40-45kg.

In the embodiment of the present invention, the pressurized electroslag remelting is performed in a 50kg pressurized electroslag remelting furnace, the maximum pressure of the pressurized electroslag remelting furnace is 7MPa, the rated power of the power supply is 500kW, the inner diameter D of the mold is 130mm, and the self-consumption power is The pole weight is 30-50kg.

In the embodiment of the present invention, the industrial pure iron contains 99.9wt% of iron, the purity of metal chromium is 99.15wt%, the purity of metal molybdenum is 99.98wt%, the purity of metal cobalt is 99.94wt%, the purity of metal tungsten is 99.95wt%, and the purity of metal vanadium is 99.95wt%. It is ≥99.9wt%, the purity of industrial silicon is 99.93wt%, the purity of metal manganese is 97.65wt%, the purity of graphite is ≥99.9wt%, the nickel-magnesium alloy contains 19.65wt% of magnesium, 80.37wt% of nickel, and the purity of cerium is ≥99.5wt% , the purity of argon in each step is ≥99.999%.

In the embodiment of the present invention, the composition of the pre-melted slag is CaF ₂ : 60±1%, Al ₂ O ₃ : 20±1%, CaO: 20±1%, and the balance is unavoidable impurities.

Example 1

Place 31.248kg of industrial pure iron, 1.575kg of metal chromium, 3.99kg of metal molybdenum, 0.63kg of metal tungsten, and 3.36kg of metal cobalt in a crucible in a vacuum induction furnace, and conduct induction at a temperature of 1505°C and a vacuum of 5Pa. Smelting to get basic molten steel;

Fill the vacuum induction furnace with argon with a purity of ≥99.999% to make the furnace pressure 0.025MPa, add 0.255kg of graphite (5% more on the basis of the target composition) to the primary molten steel under an argon atmosphere, and the graphite is melted Then start the vacuum pump to carry out vacuum carbon deoxidation, the vacuum degree of vacuum carbon deoxidation is 15Pa, the temperature is 1480 ℃, the time is 24min, and the pre-deoxidized molten steel is obtained;

Fill the furnace with argon with a purity of ≥99.999% to make the furnace pressure 0.02MPa, and add 0.126kg of metal manganese, 0.483kg of metal vanadium, 0.126kg of metal manganese to the pre-deoxidized molten steel at 1480° C. (interval 2min) in sequence Industrial silicon, 0.230kg graphite, 0.042kg nickel-magnesium alloy and 0.021kg cerium to obtain molten steel;

Casting the molten steel at 1470°C for 3 min to obtain an ingot; forging the ingot to obtain a consumable electrode with a diameter of Φ=80mm, and welding it to a dummy electrode, and clamping the dummy electrode and the electrode device connection;

Put 0.32kg arc ignition chips (1.1%C, 0.3%Si, 0.3%Mn, 3.75%Cr, 9.5%Mo, 8%Co, 1.5%W, 1.15%V and the balance of Fe) in the pressurized slag In the arc pilot ring at the center of the bottom water tank of the remelting furnace (consumable electrodes, arc pilot chips and the bottom water tank of the pressurized slag remelting furnace are in close contact); the diameter of the arc pilot ring and the water tank is 110mm, the thickness is 10mm, Gaskets made of cast iron;

After baking 3.35kg of pre-melted slag at 650℃ for 8 hours, put it into the crystallizer of the pressurized electroslag remelting furnace, and then seal the pressurized electroslag furnace; open the water supply system to pass the atmospheric cooling water into the crystallizer; The argon gas with a flow rate of 15NL/min was passed into the pressurized slag remelting furnace for 6 minutes; under the conditions of a voltage of 28V and a current of 1600A, arc slagging was carried out for 12 minutes;

After arcing and slagging, argon gas was introduced into the smelting chamber of the pressurized electroslag remelting furnace, so that the pressure in the melting chamber of the pressurized electroslag remelting furnace was 1.8 MPa, and at the same time, the pressurized electroslag remelting furnace crystallizer jacket was The pressure of the cooling water is 1.8MPa, and the electric slag remelting is carried out under the conditions of a voltage of 37V and a current of 2300A (melting rate is 50kg/h);

When the smelting of the consumable electrode is completed, the feeding and filling are carried out by gradually reducing the current, and the current is reduced every 4 minutes, and the current is reduced by 550A each time;

After the feeding is completed, turn off the AC power supply, open the gas release valve of the pressurized electroslag furnace to release the pressure, and synchronously reduce the cooling water pressure in the crystallizer of the pressurized electroslag furnace to normal pressure to obtain an electroslag ingot; placed in a thermal hood for cooling;

A coating with a thickness of 0.4 mm is applied on the surface of the electroslag ingot (powder composition: 48% SiO ₂ , 24% Al ₂ O ₃ , 16% SiC, 3% CeO ₂ , 3% CaO, 6% white mud; The binder is an aqueous solution of sodium silicate with a density of 1.38g/ ^cm3 ; the mass ratio of binder and powder is 0.6:1), and then dried at 25°C for 12h; In a heating furnace with an initial temperature of 150°C, the temperature is raised to 1130°C at a heating rate of 100°C/h, and the high temperature heat treatment is performed for 6 hours;

Preheat the hammer and anvil to 150°C, and forge the electroslag ingot after heat treatment (the opening forging temperature is 1100°C, and the final forging temperature is 980°C). When the temperature is lower than 980, it is sent back to the heating furnace for reheating; the forging is repeated 3 times to obtain a round bar with a diameter of 40 mm, and the total forging ratio is 12; and then the forged product is placed in the heating furnace according to 100 The cooling rate of ℃/h is cooled to room temperature to obtain high-cobalt and high-molybdenum superhard high-speed steel forgings.

Example 2

Place 31.992kg of industrial pure iron, 1.613kg of metal chromium, 4.085kg of metal molybdenum, 0.645kg of metal tungsten, and 3.440kg of metal cobalt in a crucible in an induction furnace, and conduct induction melting at a temperature of 1515°C and a vacuum of 7Pa. , get the basic molten steel;

Fill the vacuum induction furnace with argon with a purity of ≥ 99.999% to make the furnace pressure 0.026MPa, add 0.261kg of graphite (0.059% more on the basis of the target composition) to the basic molten steel in an argon atmosphere, and the graphite is melted Then start the vacuum pump to carry out vacuum carbon deoxidation, the vacuum degree of vacuum carbon deoxidation is 12Pa, the temperature is 1475 ℃, the time is 25min, and the pre-deoxidized molten steel is obtained;

Fill the furnace with argon gas with a purity of ≥99.999% to make the pressure in the furnace 0.03MPa, and add 0.129kg of metal manganese, 0.495kg of metal vanadium, 0.129kg of metal manganese to the pre-deoxidized molten steel at 1475°C (interval 2min) in sequence Industrial silicon, 0.240kg graphite, 0.043kg nickel-magnesium alloy and 0.022kg cerium are alloyed to obtain molten steel;

The molten steel was cooled to 1472° C., kept for 3 minutes, and then casted to obtain an ingot; the ingot was forged to obtain a consumable electrode with a diameter of Φ=80 mm, which was welded to a dummy electrode, and the dummy electrode and the electrode were welded together. Gripper connection;

Put 0.33kg of arc ignition chips (1.1%C, 0.3%Si, 0.3%Mn, 3.75%Cr, 9.5%Mo, 8%Co, 1.5%W, 1.15%V and the balance of Fe) in the pressurized slag In the arc pilot ring at the center of the bottom water tank of the remelting furnace (consumable electrodes, arc pilot chips and the bottom water tank of the pressurized slag remelting furnace are in close contact); the diameter of the arc pilot ring and the water tank is 110mm, the thickness is 10mm, Gaskets made of cast iron;

After baking 3.35kg of pre-melted slag at 650℃ for 8 hours, put it into the crystallizer of the pressurized electroslag remelting furnace, and then seal the pressurized electroslag furnace; open the water supply system to pass the atmospheric cooling water into the crystallizer; The argon gas with a flow rate of 15NL/min was fed into the pressurized slag remelting furnace for 6 minutes; under the conditions of a voltage of 27V and a current of 1600A, arc slagging was carried out for 12 minutes;

After arcing and slagging, argon gas was introduced into the smelting chamber of the pressurized electroslag remelting furnace, so that the pressure in the melting chamber of the pressurized electroslag remelting furnace was 1.8 MPa, and at the same time, the pressurized electroslag remelting furnace crystallizer jacket was The pressure of the cooling water is 1.8MPa, and the electric slag remelting is carried out under the conditions of a voltage of 38V and a current of 2250A (melting rate is 50kg/h);

When the smelting of the consumable electrode is completed, the feeding and filling are carried out by gradually reducing the current, and the current is reduced every 4 minutes, and the current is reduced by 550A each time;

After the feeding is completed, turn off the AC power supply, open the gas release valve of the pressurized electroslag furnace to release the pressure, and synchronously reduce the cooling water pressure in the crystallizer of the pressurized electroslag furnace to normal pressure to obtain an electroslag ingot; Place in a thermal hood for cooling;

The surface of the electroslag ingot is coated with a coating with a thickness of 0.45 mm (powder composition: 48% SiO ₂ , 24% Al ₂ O ₃ , 16% SiC, 3% CeO ₂ , 3% CaO, 6% white mud; The binder is an aqueous solution of sodium silicate with a density of 1.38 g/ ^cm3 ; the mass ratio of the binder and the powder is 0.6:1) after drying at 27 ° C for 10 h; the electroslag ingot coated with the coating is placed in the starting In a heating furnace with a temperature of 100 °C, the temperature is raised to 1120 °C at a heating rate of 100 °C/h, and the high temperature heat treatment is performed for 8 hours;

Preheat the hammer and anvil to 150°C, and forge the electroslag ingot after heat treatment (the opening forging temperature is 1100°C, and the final forging temperature is 980°C). When the temperature is lower than 980, it is sent back to the heating furnace for reheating; the forging is repeated 3 times to obtain a round bar with a diameter of 40 mm, and the total forging ratio is 12; then the forged product is placed in the heating furnace at 90 °C/h The cooling rate is lowered to room temperature to obtain high-cobalt and high-molybdenum superhard high-speed steel forgings.

Comparative Example 1

Place 30.504kg of industrial pure iron, 1.538kg of metal chromium, 3.895kg of metal molybdenum, 0.615kg of metal tungsten, and 3.280kg of metal cobalt in a crucible in an induction furnace, and conduct induction melting at a temperature of 1490°C and a vacuum of 6Pa. , get the basic molten steel;

Fill the vacuum induction furnace with argon with a purity of ≥99.999% to make the pressure in the furnace 0.025MPa, add 0.244kg of graphite (add 5% more on the basis of the target composition) to the basic molten steel in an argon atmosphere, and melt the graphite Then start the vacuum pump to carry out vacuum carbon deoxidation, the vacuum degree of vacuum carbon deoxidation is 14Pa, the temperature is 1510 ℃, the time is 25min, and the pre-deoxidized molten steel is obtained;

Fill the furnace with argon gas with a purity of ≥99.999% to make the pressure in the furnace 40kPa, and add 0.123kg of metal manganese, 0.472kg of metal vanadium, 0.123kg of industrial silicon to the pre-deoxidized molten steel at 1505° C. (interval of 3min) , 0.230kg graphite, 0.041kg nickel-magnesium alloy and 0.020kg cerium to obtain alloyed molten steel;

The alloyed molten steel was cooled to 1467° C., kept for 3 minutes, and then casted to obtain an ingot; the ingot was forged to obtain a consumable electrode with a diameter of Φ=80 mm, which was welded to a dummy electrode, and the dummy electrode was welded to the dummy electrode. Connect with electrode holder;

Put 0.33kg of arc ignition chips (1.1%C, 0.3%Si, 0.3%Mn, 3.75%Cr, 9.5%Mo, 8%Co, 1.5%W, 1.15%V and the balance of Fe) in the pressurized slag In the arc pilot ring at the center of the bottom water tank of the remelting furnace (consumable electrodes, arc pilot chips and the bottom water tank of the pressurized slag remelting furnace are in close contact); the diameter of the arc pilot ring and the water tank is 110mm, the thickness is 10mm, Gaskets made of cast iron;

After baking 3.3kg of pre-melted slag at 650°C for 9 hours, add it into the crystallizer of the pressurized electroslag remelting furnace, and then seal the pressurized electroslag furnace; open the water supply system to pass atmospheric cooling water into the crystallizer; The argon gas with a flow rate of 15NL/min was passed into the pressurized slag remelting furnace for 6 minutes; under the conditions of a voltage of 28V and a current of 1600A, arc slagging was carried out for 13 minutes;

After arcing and slag making, argon gas was introduced into the smelting chamber of the pressurized electroslag remelting furnace, so that the pressure in the melting chamber of the pressurized electroslag remelting furnace was 0.1 MPa, and at the same time, the pressure inside the crystallizer jacket of the pressurized electroslag remelting furnace was set to 0.1 MPa. The pressure of the cooling water is 0.1MPa, and the electric slag remelting is carried out under the conditions of a voltage of 37V and a current of 2250A (melting rate is 50kg/h);

At the end of the smelting of the consumable electrode, the feeding and filling are carried out by gradually reducing the current, and the current is reduced every 4 minutes, and the current is reduced by 550A each time;

After the feeding is completed, turn off the AC power supply, open the gas release valve of the pressurized electroslag furnace to release the pressure, and synchronously reduce the cooling water pressure in the crystallizer of the pressurized electroslag furnace to normal pressure to obtain an electroslag ingot; Place in a thermal hood for cooling;

A coating with a thickness of 0.4 mm is applied on the surface of the electroslag ingot (powder composition: 48% SiO ₂ , 24% Al ₂ O ₃ , 16% SiC, 3% CeO ₂ , 3% CaO, 6% white mud; The binder is an aqueous sodium silicate solution with a density of 1.38 g/ ^cm3 ; the mass ratio of the binder and the powder is 0.6:1) after drying at room temperature 25 ° C for 12 h; preheating the anvil to 150 ° C, will be coated with The coated electroslag ingot is heated to 1120°C in a heating furnace with a temperature of 150°C, and is forged after 1 h of heat preservation (the starting forging temperature is 1100°C and the final forging temperature is 980°C). , when the temperature is 980 ~ 1050 ℃, it is slammed, and when the temperature is lower than 980, it is sent back to the heating furnace for reheating; the forging is repeated 3 times to obtain a round bar with a diameter of 40 mm, and the total forging ratio is 12; then the forged product is placed in the heating furnace. The furnace is cooled to room temperature at a cooling rate of 90°C/h to obtain high-cobalt and high-molybdenum superhard high-speed steel forgings.

The microstructures of the electroslag ingots prepared in Examples 1 and 2 after high-temperature heat treatment were observed with a metallographic microscope, and microstructure diagrams were obtained, as shown in FIGS. 1 and 2 . The observation samples were taken from the half radius of the electroslag ingots prepared in Examples 1 and 2. It can be seen from Figures 1 and 2 that the M ₂ C eutectic carbides in the high-speed steel prepared by the preparation method provided by the present invention are fully decomposed, fractured and spheroidized, and the morphology and size of the carbides are improved.

The microstructures of the high-cobalt and high-molybdenum superhard high-speed steel forgings prepared in Examples 1 and 2 were observed with a metallographic microscope, and the microstructure diagrams were obtained, as shown in FIGS. 3 and 4 . The observation sample was taken from the central part of the high-cobalt and high-molybdenum superhard high-speed steel forgings prepared in Examples 1 and 2. It can be seen from FIG. 3 and FIG. 4 that the carbides in the high-speed steel prepared according to the preparation method provided by the present invention are finely dispersed and uniformly distributed.

5 to 7 are the surface topography diagrams of the high-cobalt and high-molybdenum superhard high-speed steel forgings prepared in Examples 1, 2 and Comparative Example 1, respectively. Comparing Figures 5 to 7, it can be seen that the high-speed steel prepared according to the preparation method of the present invention has good surface quality and no crack defects after forging, while the high-speed steel prepared by the comparative example has cracks and deep cracks on the surface after forging. Transverse cracks, indicating that the high-speed steel prepared according to the preparation method provided by the present invention has good hot workability.

Although the above embodiment has made a detailed description of the present invention, it is only a part of the embodiments of the present invention, rather than all the embodiments. People can also obtain other embodiments according to the present embodiment without creativity. These embodiments All belong to the protection scope of the present invention.

Claims (7)

1. A method for improving the hot working performance of high-cobalt high-molybdenum superhard high-speed steel comprises the following steps:

smelting industrial pure iron, a chromium-containing raw material, a molybdenum-containing raw material, metal tungsten, metal cobalt, graphite, industrial silicon, a manganese-containing raw material and a vanadium-containing raw material to obtain molten steel;

carrying out pressurized electroslag remelting on the cast ingot obtained by casting the molten steel to obtain an electroslag ingot; the solidification pressure in the pressurized electroslag remelting process is 1 to 1.8MPa;

sequentially carrying out high-temperature heat treatment and forging on the electroslag ingot to obtain a high-cobalt high-molybdenum superhard high-speed steel forging; the temperature of the high-temperature heat treatment is 1100 to 1140 ℃, and the heat preservation time is 6 to 10 hours; the heating rate of heating to the temperature required by heat treatment is 80 to 120 ℃/h; the high-cobalt high-molybdenum superhard high-speed steel forging comprises the following chemical components in percentage by mass: 0.9 to 1.2 percent of C,8 to 10 percent of Mo,7~9 percent of Co,3~5 percent of Cr,1 to 2.5 percent of W,0.7 to 1.5 percent of V,0.1 to 0.5 percent of Si,0.1 to 0.5 percent of Mn, and the balance of Fe and inevitable impurities;

the forging temperature is 1090-1120 ℃, and the finish forging temperature is 960-980 ℃; the forging times are 3~5, and the total forging ratio of forging is 12 to 16; when the temperature of the forging is above 1050 ℃, flicking to prevent the steel ingot from cracking; when the temperature of the forging is 980-1050 ℃, the heavy impact is carried out to ensure that the carbide in the forging can be broken.

2. The method according to claim 1, wherein the voltage of the pressurized electroslag remelting ranges from 33 to 40V, the current ranges from 2200 to 3000A, and the pressure ranges from 1 to 2MPa.

3. The method of claim 1, wherein the smelting comprises the steps of:

carrying out induction melting on industrial pure iron, a chromium-containing raw material, a molybdenum-containing raw material, metal tungsten and metal cobalt to obtain basic molten steel;

adding partial graphite into the basic molten steel for vacuum carbon deoxidation to obtain pre-deoxidized molten steel;

adding a manganese-containing raw material, a vanadium-containing raw material, industrial silicon and residual graphite into the pre-deoxidized molten steel for alloying to obtain molten steel.

4. The method of claim 3, wherein the induction melting temperature is 1480 to 1530 ℃.

5. The method as claimed in claim 3, wherein the vacuum degree of vacuum carbon deoxidation is less than 30Pa, the time is 20 to 30min, and the temperature is 1430 to 1480 ℃.

6. The method as claimed in claim 3, wherein the alloying temperature is 1430 to 1480 ℃ and the alloying time is 5 to 10min.

7. The method of claim 1, further comprising, prior to the high temperature heat treatment: coating the surface of the electroslag ingot with paint; the coating comprises an adhesive and powder, wherein the mass ratio of the adhesive to the powder is 0.4-0.9: 1;

the powder comprises the following components in percentage by mass: 45 to 50% SiO ₂ ，22~26% Al ₂ O ₃ ，14~18% SiC，2~4% CeO ₂ 2~4% CaO,5~8% white mud;

the adhesive is a sodium silicate aqueous solution, and the density of the adhesive is 1.36 to 1.42g/cm ³ 。

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