Preparation method of wear-resistant cast steel

Abstract

The invention relates to the technical field of metallurgical casting, and discloses a wear-resistant cast steel preparation method which comprises the following specific steps: step 1, smelting; step 2, detection: detecting the component content of the matrix alloy liquid; step 3, pouring: cooling the matrix alloy liquid to 1250-1350 DEG C, adding an alterant, heating to 1400-1480 DEG C, pouring into a mold cavity, opening the mold after the molten liquid is completely solidified, and cooling to room temperature to obtain a cast steel blank; and 4, heat treatment is conducted, and the wear-resistant steel casting is obtained. According to the preparation method, the diffusivity of carbon atoms in the matrix alloy liquid is reduced, precipitation of carbides is inhibited, meanwhile, the content of carbon and manganese is increased, the work hardening capacity of the steel casting can be improved, a high-toughness austenite structure can be kept, and the steel casting has good wear resistance during use; a traditional method of heating and then carrying out water toughening treatment is replaced by a means of quenching by waste heat after casting, so that the process can be simplified, energy can be saved, and the production period can be shortened.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical casting, and in particular to a method for preparing wear-resistant cast steel. Background Art

[0002] The wear resistance of carbon steel is mainly obtained by surface hardening. Carbon steel with W (C)> 0.35% is usually hardened by surface induction hardening or flame hardening; low carbon steel can be improved by carburizing, nitriding or carbonitriding. With the increase of hardness, its wear resistance is also enhanced accordingly. The patent document with announcement number CN105803340B in the prior art discloses a wear-resistant cast steel composed of the following components and mass percentages: C: 0.60-0.85%, Cr: 5.8-6.3%, Si: 0.6-0.8%, Mn: 0.6-0.8%, Al: 0.025-0.045%, B: 0.003-0.005%, Ti: 0.001-0.003%, S<0.03%, P<0.04%, Mo: 0.2-0.3% and Ni: 0.3-0.4%, and the balance Fe and unavoidable impurity elements. The preparation method comprises the following steps: placing alloy raw materials in a medium frequency induction furnace for melting according to the composition requirements, and maintaining the temperature of the molten steel for 5 to 10 minutes when the temperature reaches 1550 to 1600°C; pouring the molten steel into a ladle, adding 0.2 to 0.4% Al-1Ti-5B alloy to the bottom of the ladle, and pouring the molten steel into a casting mold when the temperature of the molten steel drops to 1450 to 1500°C to obtain a wear-resistant cast steel piece; and heat-treating the wear-resistant cast steel piece. The wear-resistant cast steel of the present invention is a wear-resistant cast steel that is both strong and wear-resistant.

[0003] The wear-resistant cast steel produced by this method needs to be used under high stress conditions to be fully work-hardened. However, in terms of the service conditions of wear parts, high stress conditions account for less than 5%, and most of them work under medium and low stress conditions. Therefore, existing wear-resistant cast steel parts are not easy to be work-hardened, and their high wear resistance is not brought into play. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for preparing wear-resistant cast steel.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing wear-resistant cast steel, comprising the following specific steps:

[0006] Step 1, smelting, adding scrap steel, pig iron, ferrochrome, ferromanganese, ferromolybdenum, ferroboron, ferrovanadium, aluminum ingot, zirconium ingot and niobium ingot into a high-frequency induction melting furnace, heating to 1500-1600° C. to obtain a matrix alloy liquid;

[0007] Step 2, detection, detecting the component content of the matrix alloy liquid, the mass percentage of each component element is C: 0.55-0.75%, Cr: 6.8-7.3%, Si: 0.5-0.75%, Mn: 0.65-0.85%, Al: 0.035-0.045%, B: 0.004-0.006%, Ti: 0.002-0.004%, S <0.02%, P <0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, the balance Fe and inevitable impurity elements, wear-resistant just added alloy elements including Mo, Cr, Mn, Ni, and Si, the main purpose is to improve hardenability, strength, toughness and wear resistance;

[0008] Step 3, casting, after cooling the matrix alloy liquid to 1250-1350°C, adding a modifier, heating to 1400-1480°C and pouring into the mold cavity, opening the mold after the melt is completely solidified, cooling to room temperature, and obtaining a cast steel billet;

[0009] Step 4, heat treatment, adding the cast steel blank into a heating furnace, heating it to 860-1100°C at a heating rate of 30-60°C / min, keeping it warm for 50-75min, and air cooling it to room temperature to obtain a wear-resistant cast steel part.

[0010] Preferably, when the temperature of the molten steel reaches 1550-1600°C, it is maintained for 5-10 minutes, smelting additives are added to the smelting furnace, and the slag is skimmed after standing, wherein the smelting additives include sodium borate, sodium fluorosilicate, sodium carbonate, sodium chloride, rare earth carbonate, lithium oxide and titanium dioxide, and the mass ratio thereof is 1:0.5:0.6:1.2:0.9:1.4:0.3.

[0011] Preferably, in step 4, the cast steel billet is added into a heating furnace, and argon gas is introduced so that the oxygen content in the furnace is not higher than 10%.

[0012] Preferably, in step 4, the temperature is increased to 860-950°C at a heating rate of 30-40°C / min, and kept warm for 50-65min; the temperature is increased to 950-1000°C at a heating rate of 35-50°C / min, and kept warm for 20-35min; the temperature is increased to 1000-1100°C at a heating rate of 55-60°C / min, and kept warm for 60-75min; after taking out, it is added to a salt bath at 200-250°C, kept warm for 15-25min, and after heat treatment, it is cooled to 700°C by air cooling, and then cooled to room temperature by water cooling.

[0013] Preferably, in step 3, the mold used is a sand mold, the temperature of the sand mold is raised to 750-800°C, and during the pouring process, the pouring temperature is 1250-1300°C. Alloy elements including Mo, Cr, Mn, Ni, and Si are added to the wear-resistant steel, the main purpose of which is to improve hardenability, strength, toughness and wear resistance.

[0014] The present invention has the following beneficial effects:

[0015] The wear-resistant cast steel preparation method proposed in the invention reduces the diffusion capacity of carbon atoms in the matrix alloy liquid, inhibits the precipitation of carbides, and increases the carbon and manganese content at the same time. It can not only improve the work hardening ability of the cast steel parts, but also maintain the high-toughness austenite structure, so that it has good wear resistance when used. The method of using residual heat quenching after casting replaces the traditional method of heating and then water-toughening treatment. It can not only simplify the process, save energy, shorten the production cycle, but also has significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention provides a schematic diagram of the process flow of a method for preparing wear-resistant cast steel. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0018] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0019] Example 1

[0020] Reference Figure 1 , a method for preparing wear-resistant cast steel, comprising the following specific steps:

[0021] Step 1, smelting, adding scrap steel, pig iron, ferrochrome, ferromanganese, ferromolybdenum, ferroboron, ferrovanadium, aluminum ingot, zirconium ingot and niobium ingot into a high-frequency induction melting furnace, heating to 1500-1600° C. to obtain a matrix alloy liquid;

[0022] When the temperature of the molten steel reaches 1550-1600°C, keep it for 5-10 minutes, add smelting additives into the smelting furnace, the smelting additives include sodium borate, sodium fluorosilicate, sodium carbonate, sodium chloride, rare earth carbonate, lithium oxide and titanium dioxide, and the mass ratio is 1:0.5:0.6:1.2:0.9:1.4:0.3, and then skim the slag after standing;

[0023] Step 2, detection, detecting the component content of the matrix alloy liquid, the mass percentage of each component element is C: 0.55-0.75%, Cr: 6.8-7.3%, Si: 0.5-0.75%, Mn: 0.65-0.85%, Al: 0.035-0.045%, B: 0.004-0.006%, Ti: 0.002-0.004%, S <0.02%, P <0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, the balance Fe and inevitable impurity elements;

[0024] Step 3, casting, after cooling the matrix alloy liquid to 1250-1350° C., adding a modifier, the modifier includes silicon carbide, boron nitride, tungsten oxide, silicon dioxide, metallic molybdenum and metallic magnesium, heating to 1400-1480° C. and pouring into the mold cavity, opening the mold after the melt is completely solidified, cooling to room temperature, and obtaining a cast steel billet;

[0025] Step 4, heat treatment, adding the cast steel blank into a heating furnace, heating it to 860-1100°C at a heating rate of 30-60°C / min, keeping it warm for 50-75min, and air cooling it to room temperature to obtain a wear-resistant cast steel part.

[0026] Specifically, the cast steel billet is added into a heating furnace, argon is introduced so that the oxygen content in the furnace is not higher than 10%, the temperature is increased to 860-950°C at a heating rate of 30-40°C / min, and the temperature is kept for 50-65min; the temperature is increased to 950-1000°C at a heating rate of 35-50°C / min, and the temperature is kept for 20-35min; the temperature is increased to 1000-1100°C at a heating rate of 55-60°C / min, and the temperature is kept for 60-75min; after taking out, the billet is added into a salt bath of 200-250°C and the temperature is kept for 15-25min.

[0027] In this embodiment, a wear-resistant steel casting is obtained, and the mass percentage of each component element is C: 0.55, Cr: 6.8%, Si: 0.5%, Mn: 0.65%, Al: 0.035%, B: 0.004%, Ti: 0.002%, S < 0.02%, P < 0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, and the balance is Fe and inevitable impurity elements. The wear-resistant steel casting is added with alloy elements including Mo, Cr, Mn, Ni, and Si, and the main purpose is to improve hardenability, strength, toughness and wear resistance.

[0028] Example 2

[0029] Reference Figure 1 , a method for preparing wear-resistant cast steel, comprising the following specific steps:

[0030] Step 1, smelting, adding scrap steel, pig iron, ferrochrome, ferromanganese, ferromolybdenum, ferroboron, ferrovanadium, aluminum ingot, zirconium ingot and niobium ingot into a high-frequency induction melting furnace, heating to 1500-1600° C. to obtain a matrix alloy liquid;

[0031] When the temperature of the molten steel reaches 1550-1600°C, keep it for 5-10 minutes, add smelting additives into the smelting furnace, the smelting additives include sodium borate, sodium fluorosilicate, sodium carbonate, sodium chloride, rare earth carbonate, lithium oxide and titanium dioxide, and the mass ratio is 1:0.5:0.6:1.2:0.9:1.4:0.3, and then skim the slag after standing;

[0032] Step 2, detection, detecting the component content of the matrix alloy liquid, the mass percentage of each component element is C: 0.55-0.75%, Cr: 6.8-7.3%, Si: 0.5-0.75%, Mn: 0.65-0.85%, Al: 0.035-0.045%, B: 0.004-0.006%, Ti: 0.002-0.004%, S <0.02%, P <0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, the balance Fe and inevitable impurity elements;

[0033] Step 3, casting, after cooling the matrix alloy liquid to 1250-1350° C., adding a modifier, the modifier includes silicon carbide, boron nitride, tungsten oxide, silicon dioxide, metallic molybdenum and metallic magnesium, heating to 1400-1480° C. and pouring into the mold cavity, opening the mold after the melt is completely solidified, cooling to room temperature, and obtaining a cast steel billet;

[0034] The mold used is a sand mold, the temperature of the sand mold rises to 750-800°C, and during the pouring process, the pouring temperature is 1250-1300°C.

[0035] Step 4, heat treatment, adding the cast steel blank into the heating furnace, heating it to 860-1100°C at a heating rate of 30-60°C / min, keeping it warm for 50-75min, cooling it to 700°C by air cooling after heat treatment, and then cooling it to room temperature by water cooling to obtain a wear-resistant cast steel part.

[0036] Specifically, the cast steel billet is added into a heating furnace, argon is introduced so that the oxygen content in the furnace is not higher than 10%, the temperature is increased to 860-950°C at a heating rate of 30-40°C / min, and the temperature is kept for 50-65min; the temperature is increased to 950-1000°C at a heating rate of 35-50°C / min, and the temperature is kept for 20-35min; the temperature is increased to 1000-1100°C at a heating rate of 55-60°C / min, and the temperature is kept for 60-75min; after being taken out, the billet is added into a salt bath of 200-250°C and the temperature is kept for 15-25min.

[0037] In this embodiment, the obtained wear-resistant steel casting has the following mass percentages: C: 0.75%, Cr: 7.3%, Si: 0.75%, Mn: 0.85%, Al: 0.045%, B: 0.006%, Ti: 0.004%, S < 0.02%, P < 0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, the remainder being Fe and inevitable impurity elements. The wear-resistant steel casting is added with alloy elements including Mo, Cr, Mn, Ni, and Si, the main purpose of which is to improve hardenability, strength, toughness and wear resistance. The multi-element low-alloy steel with W (C) = 0.75% has high hardness, good wear resistance, good strength and toughness combination, and is not easy to deform or break during use after water quenching and tempering.

[0038] The wear-resistant alloy cast steel obtained was tested for performance, and the test method and test results are as follows:

[0039] A. Scanning electron microscopy-EBSD was used to analyze the volume fraction of precipitated carbides in wear-resistant alloy cast steel;

[0040] B. The tensile test is carried out in accordance with GB / T228-2010 Tensile test for metal materials;

[0041] C. Hardness test is carried out in accordance with GB / T230.1-2018 Metal Rockwell Hardness Test;

[0042] D. Impact toughness is carried out according to GB / T 229-2007 Charpy pendulum impact test method for metal materials;

[0043] E. The wear resistance test is evaluated using the China Foundry Association standard T-CFA010604-3-2016 steel material impact abrasive wear test method.

[0044]

[0045] It can be seen from the above table that the wear resistance of Example 1 and Example 2 is significantly better than that of the comparative example. In the comparative example, Cr15 high chromium cast iron is a currently commonly used low-carbon wear-resistant alloy cast steel. The present invention optimizes the ratio and preparation method to provide the wear-resistant alloy cast steel with higher wear resistance.

[0046] The wear-resistant cast steel preparation method proposed in the invention reduces the diffusion capacity of carbon atoms in the matrix alloy liquid, inhibits the precipitation of carbides, and increases the carbon and manganese content at the same time. It can not only improve the work hardening ability of the cast steel parts, but also maintain the high-toughness austenite structure, so that it has good wear resistance when used. The method of using residual heat quenching after casting replaces the traditional method of heating and then water-toughening treatment. It can not only simplify the process, save energy, shorten the production cycle, but also has significant economic benefits.

[0047] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing wear-resistant cast steel, characterized in that: The specific steps include: Step 1, smelting, adding scrap steel, pig iron, ferrochrome, ferromanganese, ferromolybdenum, ferroboron, ferrovanadium, aluminum ingot, zirconium ingot and niobium ingot into a high-frequency induction melting furnace, heating to 1500-1600° C. to obtain a matrix alloy liquid; Step 2, detection, detecting the component content of the matrix alloy liquid, the mass percentage of each component element is C: 0.55-0.75%, Cr: 6.8-7.3%, Si: 0.5-0.75%, Mn: 0.65-0.85%, Al: 0.035-0.045%, B: 0.004-0.006%, Ti: 0.002-0.004%, S <0.02%, P <0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, the balance Fe and inevitable impurity elements; Step 3, casting, after cooling the matrix alloy liquid to 1250-1350°C, adding a modifier, heating to 1400-1480°C and pouring into the mold cavity, opening the mold after the melt is completely solidified, cooling to room temperature, and obtaining a cast steel billet; Step 4, heat treatment, adding the cast steel blank into a heating furnace, heating it to 860-1100°C at a heating rate of 30-60°C / min, keeping it warm for 50-75min, and air cooling it to room temperature to obtain a wear-resistant cast steel part.

2. The method for preparing wear-resistant cast steel according to claim 1, characterized in that: When the temperature of the molten steel reaches 1550-1600°C, it is maintained for 5-10 minutes, smelting additives are added into the smelting furnace, and the slag is removed after standing.

3. A method for preparing wear-resistant cast steel according to claim 2, characterized in that: The smelting additives include sodium borate, sodium fluorosilicate, sodium carbonate, sodium chloride, rare earth carbonate, lithium oxide and titanium dioxide, and the mass ratio thereof is 1:0.5:0.6:1.2:0.9:1.4:0.

3.

4. A method for preparing wear-resistant cast steel according to claim 3, characterized in that: In step 4, the cast steel billet is placed in a heating furnace, and argon gas is introduced to ensure that the oxygen content in the furnace is not higher than 10%.

5. A method for preparing wear-resistant cast steel according to claim 4, characterized in that: In the step 4, the temperature is increased to 860-950°C at a heating rate of 30-40°C / min, and kept warm for 50-65min; the temperature is increased to 950-1000°C at a heating rate of 35-50°C / min, and kept warm for 20-35min; the temperature is increased to 1000-1100°C at a heating rate of 55-60°C / min, and kept warm for 60-75min; after taking out, it is added to a salt bath of 200-250°C and kept warm for 15-25min.

6. A method for preparing wear-resistant cast steel according to claim 5, characterized in that: The wear-resistant cast steel part obtained comprises the following components in percentage by mass: C: 0.55, Cr: 6.8%, Si: 0.5%, Mn: 0.65%, Al: 0.035%, B: 0.004%, Ti: 0.002%, S < 0.02%, P < 0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, with the remainder being Fe and unavoidable impurity elements.

7. A method for preparing wear-resistant cast steel according to claim 5, characterized in that: In step 3, the mold used is a sand mold, the temperature of the sand mold rises to 750-800°C, during the pouring process, the pouring temperature is 1250-1300°C, after heat treatment, it is cooled to 700°C by air cooling, and then cooled to room temperature by water cooling.

8. A method for preparing wear-resistant cast steel according to claim 7, characterized in that: The wear-resistant steel casting obtained comprises the following components: C: 0.75%, Cr: 7.3%, Si: 0.75%, Mn: 0.85%, Al: 0.045%, B: 0.006%, Ti: 0.004%, S < 0.02%, P < 0.05%, Mo: 0.3-0.45% and Ni: 0.25-0.35%, with the remainder being Fe and unavoidable impurity elements.

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