CN107937813A - A kind of CrNiWCo two-phase alloys steel and preparation method thereof - Google Patents

Abstract

A CrNiWCo dual-phase alloy steel and a preparation method thereof, which relate to a dual-phase alloy steel and a preparation method thereof. The purpose of the invention is to solve the problem that the yield strength and tensile strength of the existing duplex stainless steel are still relatively low. CrNiWCo dual-phase alloy steel is prepared from C, Cr, Ni, Mn, Mo, W, Co, Sc, Al, V, S, P and the balance is Fe. Preparation method: 1. Melting sequentially through electric arc furnace → LF furnace → VOD furnace; 2. High temperature tapping, natural cooling, rapid forging and rolling, high temperature diffusion tempering, and natural cooling treatment to obtain CrNiWCo dual-phase alloy steel . Advantages: The yield strength at room temperature is above 900MPa, the tensile strength is above 1100MPa, and at a temperature of 800°C, the yield strength is above 250MPa, and the tensile strength is above 250MPa. The invention is mainly used for preparing CrNiWCo dual-phase alloy steel.

Description

A kind of CrNiWCo dual-phase alloy steel and its preparation method

technical field

The invention relates to a dual-phase alloy steel and a preparation method thereof.

Background technique

Since duplex stainless steel was born in the United States in the 1940s, it has developed to the third generation. Duplex stainless steel has the characteristics of austenitic stainless steel and ferritic stainless steel because it has austenite + ferrite duplex structure, and the content of the two phase structures is basically the same. The yield strength can reach 400MPa~550MPa, which is twice that of ordinary austenitic stainless steel. Compared with ferritic stainless steel, duplex stainless steel has high toughness, low brittle transition temperature, significantly improved intergranular corrosion resistance and welding performance; at the same time, it retains some characteristics of ferritic stainless steel, such as 475 ℃ brittleness, thermal High conductivity, small coefficient of linear expansion, superplasticity and magnetism. Compared with austenitic stainless steel, the strength of duplex stainless steel is high, especially the yield strength is significantly improved, and the performance of pitting corrosion resistance, stress corrosion resistance, and corrosion fatigue resistance is also significantly improved. Duplex stainless steel is classified according to its chemical composition and can be divided into four types: Cr18 type, Cr23 (excluding Mo), Cr22 type and Cr25 type. However, the yield strength and tensile strength of existing duplex stainless steels are still low.

Contents of the invention

The purpose of the present invention is to solve the problem that the yield strength and tensile strength of the existing duplex stainless steel are still low, and provide a CrNiWCo duplex alloy steel and a preparation method thereof.

A CrNiWCo dual-phase alloy steel consists of 0.03%-0.08%C, 8%-11%Cr, 4%-7%Ni, 0.3%-0.5%Mn, 0.6%-1%Mo, 1%-3% %W, 0.3%-0.5% Co, 0.5%-2% Sc, 0.1%-2% Al, 0.2%-1% V, 0.007% S, 0.02% P and the balance is Fe.

A kind of preparation method of CrNiWCo dual-phase alloy steel is specifically finished according to the following steps:

1. Smelting: Prepare smelting raw materials according to actual needs, put the prepared smelting raw materials into the electric arc furnace in turn, smelt until the smelting raw materials are completely melted, then transfer to the LF furnace, and smelt at a temperature of 1500 ° C ~ 1550 ° C for 10 min ~ 15 min. Then transfer to the VOD furnace and melt at a temperature of 1600°C to 1650°C for 10min to 15min to obtain a melt;

2. Forming: Send the melt obtained in step 1 into the mold at a temperature of 1500°C, and obtain a steel ingot after natural cooling. The steel ingot undergoes rapid forging and rolling in turn to obtain rolled steel. The rapid forging temperature is 950°C to 1050°C. ℃, the rolling temperature is 950 ℃ ~ 1050 ℃, the rolled steel is subjected to high temperature diffusion tempering at 1050 ℃ and then naturally cooled to obtain CrNiWCo dual-phase alloy steel; the mass fraction of C in the CrNiWCo dual-phase alloy steel 0.03%-0.08%, Cr mass fraction 8%-11%, Ni mass fraction 4%-7%, Mn mass fraction 0.3%-0.5%, Mo mass fraction 0.6%-1%, W mass fraction 1%-3%, Co mass fraction 0.3%-0.5%, Sc mass fraction 0.5%-2%, Al mass fraction 0.1%-2%, V mass fraction 0.2%-1%, S mass fraction is 0.007%, the mass fraction of P is 0.02%, and the balance is Fe.

Advantages of the present invention: the CrNiWCo dual-phase alloy steel prepared by the present invention has the characteristics of yield strength, tensile strength and high temperature resistance. The yield strength at room temperature reaches more than 900 MPa, the tensile strength reaches more than 1100 MPa, and the impact energy at room temperature reaches more than 30J. At 800°C, the yield strength reaches more than 250MPa, and the tensile strength reaches more than 250MPa. Therefore, the CrNiWCo dual-phase alloy steel prepared by the present invention has high strength, corrosion resistance, erosion resistance and micromagnetic properties under high temperature environments, so it has extremely Extensive market demand covers many advanced manufacturing fields.

Description of drawings

Fig. 1 is the SEM image of the CrNiWCo dual-phase alloy steel prepared in Example 3.

Detailed ways

Specific embodiment one: This embodiment is a CrNiWCo dual-phase alloy steel, characterized in that the CrNiWCo dual-phase alloy steel consists of 0.03% to 0.08% C, 8% to 11% Cr, 4% to 7% Ni, 0.3%～0.5%Mn, 0.6%～1%Mo, 1%～3%W, 0.3%～0.5%Co, 0.5%～2%Sc, 0.1%～2%Al, 0.2%～1%V, 0.007 %S, 0.02%P and the rest are prepared from Fe.

Cr is a medium carbide forming element. Among all kinds of carbides, chromium carbide is the smallest one. It can be evenly distributed in the steel volume, so it has high strength, hardness, yield strength and wear resistance. . Because it can refine and evenly distribute the structure, it has good plasticity and toughness, which is especially valuable for tool steel. The carbide of Cr is also difficult to dissolve, and it can hinder the growth of grains under short-term heating, and the carburization will also coarsen the grains for a long time. So the overheating sensitive effect can be reduced. Cr can slow down the decomposition rate of A body and reduce the critical cooling rate during quenching, thus contributing to the formation of M body and improving the stability of M body, so Cr steels have excellent hardenability and small quenching deformation. Note: Cr is a ferrite-forming element, which reduces the γ region, so when there is no A-body element present, the high-Cr steel will have a ferrite structure. The combination of Cr and W or Mo can increase the retained austenite in the quenched steel, and help to obtain the carbide phase that needs to be pulverized. Cr can greatly improve the strength and plasticity of structural steel, and this effect is especially significant in the steel combined with Cr and Ni. And adding Ni to Cr can also greatly improve the corrosion resistance of steel. The effect of Cr on improving corrosion resistance will decrease with the increase of carbon content, because the combination of Cr and C has no effect.

This embodiment utilizes the beneficial effect of Ni in the alloy. Pure nickel steel is rarely used in industry at present. This is due to the fact that nickel works better when used in combination with other alloying elements. The main effect of nickel is that it changes the crystal structure of stainless steel. Adding nickel element in stainless steel can significantly improve the plasticity, weldability, toughness and other properties of stainless steel. Nickel imparts a face centered cubic structure (FCC) to the austenite. Therefore nickel element is called austenite forming element. The crystal structure of ordinary carbon steel is called ferrite, which has a body-centered cubic (BCC) structure. The addition of nickel promotes the crystal structure from a body-centered cubic (BCC) structure to a face-centered cubic (FCC) structure. This structure is called Austrian. body. In addition, nickel can also expand the passivation range of stainless steel in non-oxidizing media, and effectively improve the repassivation ability of stainless steel. Nickel is an excellent corrosion-resistant material, especially for strong alkaline media. The strength and plasticity of nickel are also very good, and it can withstand various pressure processing. In addition to the role of forming austenite, nickel in stainless steel can also expand the passivation range of stainless steel in non-oxidizing media, and effectively improve the repassivation ability of stainless steel. However, nickel as a single alloying element must reach a considerable concentration (about 27%) to make stainless steel meet the corrosion resistance requirements of certain medium environments. Therefore, nickel is generally not used alone as the only alloying element to form stainless steel. Usually coexist with chromium in stainless steel and become an important branch of chromium-nickel austenitic stainless steel. Experiments have proved that nickel-containing stainless steel is especially suitable for carburized parts that require surface hardening treatment. It can obtain a surface layer with high hardness and good toughness to resist wear and corrosion. Nickel-containing steel is prone to banding and white spot defects, and necessary measures must be taken during the production process to prevent the above defects.

The purpose of adding Co in this embodiment, due to the characteristics of Co, the role of Co in this embodiment is to refine the structure and grain, increase the strength and plasticity of the alloy, improve the high temperature resistance of the alloy and reduce hardening sex. Therefore, in the fusion with Ni, the required plasticity of the alloy is formed and maintained, and the hardness of the alloy is increased.

The purpose of adding W in this embodiment is that W is a high temperature resistant element and tungsten has wear resistance at high temperature. The tungsten added in this embodiment is evenly distributed in the dimples of the metal in the form of fine compounds in the alloy. This can play a role in the alloy's wear resistance in high temperature environments.

The purpose of adding Mo in this embodiment is to form stable carbides in the recombination of Mo and Cr to improve the tempering resistance.

The purpose of adding V in this embodiment is to refine the grain structure and improve the strength and toughness during the fusion of V and other elements in the alloy.

The purpose of adding Sc in this embodiment is to add a small amount of Sc to the alloy in this embodiment to improve the strength of the alloy and increase the hardness and heat resistance of the alloy.

The purpose of adding Al in this embodiment is that when Al is fused with other alloying elements, it can refine the microstructure grains and increase the strength of the alloy. In particular, Al is dispersed in the grain boundaries of the alloy to play a certain role in resisting intergranular corrosion.

Embodiment 2: The difference between this embodiment and Embodiment 1 is that the CrNiWCo dual-phase alloy steel consists of 0.03%C, 8%Cr, 4%Ni, 0.3%Mn, 0.6%Mo, 1 %W, 0.3% Co, 0.5% Sc, 0.1% Al, 0.2% V, 0.007% S, 0.02% P and the balance is Fe. Others are the same as the first embodiment.

Specific embodiment three: the difference between this embodiment and specific embodiment one is: the CrNiWCo dual-phase alloy steel is composed of 0.05%C, 9.5%Cr, 5.5%Ni, 0.4%Mn, 0.8%Mo, 2 %W, 0.4% Co, 1.25% Sc, 0.55% Al, 0.6% V, 0.007% S, 0.02% P and the balance is Fe. Others are the same as the first embodiment.

Embodiment 4: The difference between this embodiment and Embodiment 1 is that the CrNiWCo dual-phase alloy steel consists of 0.08%C, 11%Cr, 7%Ni, 0.5%Mn, 1%Mo, 3 %W, 0.5% Co, 2% Sc, 2% Al, 1% V, 0.007% S, 0.02% P and the balance is Fe. Others are the same as the first embodiment.

Specific embodiment five: This embodiment is a preparation method of CrNiWCo dual-phase alloy steel, which is specifically completed according to the following steps:

1. Smelting: Prepare smelting raw materials according to actual needs, put the prepared smelting raw materials into the electric arc furnace in turn, smelt until the smelting raw materials are completely melted, then transfer to the LF furnace, and smelt at a temperature of 1500 ° C ~ 1550 ° C for 10 min ~ 15 min. Then transfer to the VOD furnace and melt at a temperature of 1600°C to 1650°C for 10min to 15min to obtain a melt;

2. Forming: Send the melt obtained in step 1 into the mold at a temperature of 1500°C, and obtain a steel ingot after natural cooling. The steel ingot undergoes rapid forging and rolling in turn to obtain rolled steel. The rapid forging temperature is 950°C to 1050°C. ℃, the rolling temperature is 950 ℃ ~ 1050 ℃, the rolled steel is subjected to high temperature diffusion tempering at 1050 ℃ and then naturally cooled to obtain CrNiWCo dual-phase alloy steel; the mass fraction of C in the CrNiWCo dual-phase alloy steel 0.03%-0.08%, Cr mass fraction 8%-11%, Ni mass fraction 4%-7%, Mn mass fraction 0.3%-0.5%, Mo mass fraction 0.6%-1%, W mass fraction 1%-3%, Co mass fraction 0.3%-0.5%, Sc mass fraction 0.5%-2%, Al mass fraction 0.1%-2%, V mass fraction 0.2%-1%, S mass fraction is 0.007%, the mass fraction of P is 0.02%, and the balance is Fe.

Embodiment 6: The difference between this embodiment and Embodiment 5 is that the shape of the CrNiWCo dual-phase alloy steel described in step 2 is plate, rod or tube. Others are the same as in Embodiment 6.

The delivery state of the plates, rods or tubes described in this embodiment should meet the national standard.

Adopt following test verification effect of the present invention

Embodiment 1: a kind of preparation method of CrNiWCo dual-phase alloy steel, specifically finish according to the following steps:

1. Smelting: Prepare the smelting raw materials according to actual needs, put the prepared smelting raw materials into the electric arc furnace in turn, smelt until the smelting raw materials are completely melted, then transfer to the LF furnace, melt at a temperature of 1500 ° C for 10 minutes, and then transfer to the VOD furnace In the process, melt at a temperature of 1650°C for 10 minutes to obtain a melt;

2. Forming: Send the melt obtained in step 1 into the mold at a temperature of 1500°C, and obtain a steel ingot after natural cooling. The steel ingot undergoes rapid forging and rolling in sequence to obtain rolled steel. The processing temperature is 1000°C, and the rolled steel is subjected to high-temperature diffusion tempering at a temperature of 1050°C and then naturally cooled to obtain CrNiWCo dual-phase alloy steel; the mass fraction of C in the CrNiWCo dual-phase alloy steel is 0.03%, and the mass fraction of Cr is The mass fraction of Ni is 8%, the mass fraction of Ni is 4%, the mass fraction of Mn is 0.3%, the mass fraction of Mo is 0.6%, the mass fraction of W is 1%, the mass fraction of Co is 0.3%, the mass fraction of Sc is 0.5%, the mass fraction of Al is 0.1%, V mass fraction is 0.2%, S mass fraction is 0.007%, P mass fraction is 0.02% and the balance is Fe.

The shape of the CrNiWCo dual-phase alloy steel in this embodiment is rod-like.

Adopt the preparation method of a kind of CrNiWCo duplex alloy steel of embodiment 1 to prepare two test pieces altogether, be sample A and sample B, test sample A and sample B, test result is as shown in table 1, It can be seen from Table 1 that the average tensile strength of CrNiWCo dual-phase alloy steel prepared in this example at room temperature is 1142MPa, the average yield strength at room temperature is 944.5MPa, the average elongation at room temperature is 13.3%, the average impact energy at room temperature is 34J, and the average tensile strength at 800°C It is 270MPa, the average yield strength at 800°C is 259MPa, and the average elongation at 800°C is 17.95%.

Table 1

The sample A obtained in Example 1 was kept at a temperature of 760° C. for 1 h, and then water quenched. Select 10 points in sample A to test the hardness, select HV50, the hardness is 378, 364, 361, 369, 368, 360, 383, 357, 357 and 361, and the average value is 365.8. Converted to Rockwell hardness/HRC is 37.2.

The sample B obtained in Example 1 was kept at a temperature of 760° C. for 1 h, and then water quenched. Select 10 points in sample B to test the hardness, select HV50, the hardness is 350, 356, 370, 367, 369, 373, 371, 388, 378 and 371, and the average value is 369.3. Converted to Rockwell hardness/HRC is 37.7.

Embodiment 2: a kind of preparation method of CrNiWCo dual-phase alloy steel, specifically finish according to the following steps:

1. Smelting: Prepare the smelting raw materials according to actual needs, put the prepared smelting raw materials into the electric arc furnace in turn, smelt until the smelting raw materials are completely melted, then transfer to the LF furnace, smelt at a temperature of 1550 ° C for 15 minutes, and then transfer to the VOD furnace In the process, melt at a temperature of 1650°C for 10 minutes to obtain a melt;

2. Forming: Send the melt obtained in step 1 into the mold at a temperature of 1500°C, and obtain a steel ingot after natural cooling. The steel ingot undergoes rapid forging and rolling in sequence to obtain rolled steel. The processing temperature is 1000°C, and the rolled steel is subjected to high-temperature diffusion tempering at a temperature of 1050°C and then naturally cooled to obtain CrNiWCo dual-phase alloy steel; the mass fraction of C in the CrNiWCo dual-phase alloy steel is 0.05%, and the mass fraction of Cr is The mass fraction of Ni is 9.5%, the mass fraction of Ni is 5.5%, the mass fraction of Mn is 0.4%, the mass fraction of Mo is 0.8%, the mass fraction of W is 2%, the mass fraction of Co is 0.4%, the mass fraction of Sc is 1.25%, the mass fraction of Al is 0.55%, V mass fraction is 0.6%, S mass fraction is 0.007%, P mass fraction is 0.02% and the balance is Fe.

The shape of the CrNiWCo dual-phase alloy steel in this embodiment is rod-like.

Adopt the preparation method of a kind of CrNiWCo duplex alloy steel of embodiment 2 to prepare two specimens altogether, be sample C and sample D, sample C and sample D are detected, and detection result is as shown in table 2, It can be seen from Table 2 that the average tensile strength of the CrNiWCo dual-phase alloy steel prepared in this example at room temperature is 1182.5MPa, the average yield strength at room temperature is 987.5MPa, the average elongation at room temperature is 13.6%, the average room temperature impact energy is 33.7J, and the average tensile strength at room temperature is 33.7J. The tensile strength is 293.5MPa, the average yield strength at 800°C is 275MPa, and the average elongation at 800°C is 17.4%.

Table 2

Sample C and sample D obtained in Example 2 were kept at a temperature of 760° C. for 1 hour, and then water quenched to detect the impact energy of sample C and sample D. The impact energy at room temperature was 32.5J and 32.9J, respectively.

Sample C and sample D obtained in Example 2 were kept at a temperature of 962°C for 1 hour, then quenched in water, and 5 points of sample C were selected for hardness testing, HV50 was selected, and the hardnesses were 351, 355, 355, and 356 respectively. and 362, with an average of 355.8. Converted to Rockwell hardness/HRC is 36.1.

Embodiment 3: a kind of preparation method of CrNiWCo dual-phase alloy steel, specifically finish according to the following steps:

1. Smelting: Prepare the smelting raw materials according to actual needs, put the prepared smelting raw materials into the electric arc furnace in turn, smelt until the smelting raw materials are completely melted, then transfer to the LF furnace, smelt at a temperature of 1550 ° C for 15 minutes, and then transfer to the VOD furnace In the process, smelting at a temperature of 1600°C for 15 minutes to obtain a melt;

2. Forming: Send the melt obtained in step 1 into the mold at a temperature of 1500°C, and obtain a steel ingot after natural cooling. The steel ingot undergoes rapid forging and rolling in sequence to obtain rolled steel. The processing temperature is 1000°C, and the rolled steel is subjected to high temperature diffusion tempering at a temperature of 1050°C and then naturally cooled to obtain CrNiWCo dual-phase alloy steel; the mass fraction of C in the CrNiWCo dual-phase alloy steel is 0.08%, and the mass fraction of Cr is 0.08%. 11%, Ni 7%, Mn 0.5%, Mo 1%, W 3%, Co 0.5%, Sc 2%, Al is 2%, V mass fraction is 1%, S mass fraction is 0.007%, P mass fraction is 0.02% and the balance is Fe.

The SEM image of the CrNiWCo dual-phase alloy steel prepared in this example is shown in FIG. 1 , and FIG. 1 is the SEM image of the CrNiWCo dual-phase alloy steel prepared in Example 3.

Claims (6)

1. A kind of 1. CrNiWCo two-phase alloys steel, it is characterised in that CrNiWCo two-phase alloys steel by mass fraction by 0.03%~ 0.08%C, 8%~11%Cr, 4%~7%Ni, 0.3%~0.5%Mn, 0.6%~1%Mo, 1%~3%W, 0.3%~ 0.5%Co, 0.5%~2%Sc, 0.1%~2%Al, 0.2%~1%V, 0.007%S, 0.02%P and surplus are prepared for Fe Form.
2. A kind of 2. CrNiWCo two-phase alloys steel according to claim 1, it is characterised in that the CrNiWCo two-phase alloys Steel is by mass fraction by 0.03%C, 8%Cr, 4%Ni, 0.3%Mn, 0.6%Mo, 1%W, 0.3%Co, 0.5%Sc, 0.1% Al, 0.2%V, 0.007%S, 0.02%P and surplus are prepared for Fe.
3. A kind of 3. CrNiWCo two-phase alloys steel according to claim 1, it is characterised in that the CrNiWCo two-phase alloys Steel by mass fraction by 0.05%C, 9.5%Cr, 5.5%Ni, 0.4%Mn, 0.8%Mo, 2%W, 0.4%Co, 1.25%Sc, 0.55%Al, 0.6%V, 0.007%S, 0.02%P and surplus are prepared for Fe.
4. A kind of 4. CrNiWCo two-phase alloys steel according to claim 1, it is characterised in that the CrNiWCo two-phase alloys Steel is by mass fraction by 0.08%C, 11%Cr, 7%Ni, 0.5%Mn, 1%Mo, 3%W, 0.5%Co, 2%Sc, 2%Al, 1% V, 0.007%S, 0.02%P and surplus are prepared for Fe.
5. A kind of a kind of 5. preparation method of CrNiWCo two-phase alloys steel, it is characterised in that preparation side of CrNiWCo two-phase alloys steel Method is completed according to the following steps：

   First, melting：Prepare melting raw material according to actual needs, melting raw material will be prepared and be sequentially loaded into electric arc furnaces, melting to melting Raw material is completely melt, is then transferred in LF stoves, and melting 10min~15min at being 1500 DEG C~1550 DEG C in temperature, retransfers Into VOD stoves, melting 10min~15min at being 1600 DEG C~1650 DEG C in temperature, obtains melt；

   2nd, it is molded：The melt for obtaining step 1 at being 1500 DEG C in temperature is sent into mould, and steel ingot is obtained after natural cooling, Steel ingot through too fast forging and rolling, obtains rolled steel successively, and fast temperature of forging is 950 DEG C~1050 DEG C, rolling temperature for 950 DEG C~ 1050 DEG C, natural cooling is handled after rolled steel carries out High temperature diffusion tempering at being 1050 DEG C in temperature, that is, it is double to obtain CrNiWCo Phase alloy steel；In the CrNiWCo two-phase alloys steel C mass fractions be 0.03%~0.08%, Cr mass fractions be 8%~ 11%th, Ni mass fractions are 4%~7%, Mn mass fractions are 0.3%~0.5%, Mo mass fractions are 0.6%~1%, W matter Amount fraction is 1%~3%, Co mass fractions are 0.3%~0.5%, Sc mass fractions are 0.5%~2%, Al mass fractions are 0.1%~2%, V mass fractions are 0.2%~1%, S mass fractions are 0.007%, P mass fractions are 0.02% and surplus is Fe。
6. A kind of 6. preparation method of CrNiWCo two-phase alloys steel according to claim 1, it is characterised in that institute in step 2 The shape for the CrNiWCo two-phase alloys steel stated is tabular, bar-shaped or tubulose.