High-hardness and high-toughness wear-corrosion-resistant cast steel material and gradient heat treatment preparation method thereof

Abstract

The invention discloses a high-hardness and high-toughness wear-resistant cast steel material and a gradient heat treatment preparation method thereof, and relates to the technical field of metal materials, the high-hardness and high-toughness wear-resistant cast steel material comprises the following raw materials by weight percentage: 0.35%-0.5% of C, 14%-16% of Cr, 1.8%-2.2% of Mo, 0.8%-1.2% of Ni, 0.02%-0.05% of B and 0.08%-0.12% of mischmetal. A hard and tough synergistic layer is formed through C, Cr, Mo and Ni, C can balance hardness and casting fluidity, Cr forms a passive film, Mo can inhibit temper brittleness, Ni improves low-temperature toughness, B is added to preferentially form a B-Cr compound, a grain boundary corrosion channel can be blocked, mixed rare earth is adopted to replace pure rare earth, the cost is greatly reduced, and the service life is prolonged. The cast steel material prepared from the raw materials in percentage by weight not only has better impact wear resistance, but also has better corrosion resistance, and meanwhile, the cost of the production raw materials is also reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to a high-hardness, toughness, and wear-resistant cast steel material and a gradient heat treatment preparation method thereof. Background Art

[0002] With the development of the metal materials industry, a variety of metal materials have emerged. Metal materials refer to materials with properties such as luster, ductility, and good electrical and thermal conductivity. They are generally divided into ferrous metals and non-ferrous metals. Ferrous metals include iron, chromium, and manganese. Among them, steel is the basic structural material and is called the "backbone of industry."

[0003] At present, during the use of equipment such as mining machinery liners, ship propellers and hydropower turbine blades made of metal materials, due to the particularity of the operating environment, there are relatively strict requirements on the impact wear resistance and corrosion resistance of metal materials.

[0004] In the above usage scenarios, some cast steel materials made of metal materials have some problems, such as high chromium cast iron: hardness ≥ 60HRC, but impact toughness < 10J / cm 2 , easy to crack; duplex stainless steel: good corrosion resistance, but the hardness is only 35-40HRC, and the wear resistance is insufficient. For this reason, we propose a high hardness, toughness, and wear-resistant cast steel material and its gradient heat treatment preparation method. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-hardness, toughness, and wear-resistant cast steel material and a gradient heat treatment preparation method thereof. The cast steel material made from raw materials calculated in percentage by weight not only has good impact wear resistance, but also has good corrosion resistance. It is suitable for mining machinery liners, ship propellers, hydropower turbine blades, and other harsh working conditions that are subjected to impact wear and corrosion at the same time.

[0006] To achieve the above object, the present invention provides the following technical solution: a high-hardness, toughness, and wear-resistant cast steel material, comprising the following raw materials in percentage by weight, specifically:

[0007] C 0.35% ~ 0.5%, Cr 14% ~ 16%, Mo 1.8% ~ 2.2%, Ni 0.8% ~ 1.2%, B 0.02% ~ 0.05% and mixed rare earth 0.08% ~ 0.12%.

[0008] Preferably, the mixed rare earth is a mixture of La and Ce, and the weight ratio of La to Ce in the mixture is 3:1.

[0009] Preferably, the ratio of Cr, Mo and C in the raw material satisfies: (Cr+Mo) / C≥35.

[0010] Preferably, the cast steel material further comprises the following raw materials in percentage by weight, specifically:

[0011] C0.35%, Cr14%, Mo1.8%, Ni0.8%, B0.02% and mixed rare earth 0.08%.

[0012] Preferably, the cast steel material further comprises the following raw materials in percentage by weight, specifically:

[0013] C0.5%, Cr16%, Mo2.2%, Ni1.2%, B0.05% and mixed rare earth 0.12%.

[0014] Preferably, the cast steel material further comprises the following raw materials in percentage by weight, specifically:

[0015] C0.42%, Cr15.2%, Mo2%, Ni1%, B0.03% and mixed rare earth 0.1%.

[0016] In a second aspect, the present invention provides a gradient heat treatment preparation method, which implements the high hardness, toughness, and wear-resistant cast steel material as described above, and the specific steps of the method are as follows:

[0017] Step 1: Smelting in an intermediate frequency furnace: take out a certain amount of raw materials according to the above weight percentage, and then put them into the intermediate frequency furnace for melting. Set the intermediate frequency furnace melting processing time and the intermediate frequency furnace melting frequency until all the raw materials are completely melted into slurry;

[0018] Step 2: Argon protection pouring: Use the control button to control the medium frequency furnace to slowly reduce the power of the medium frequency furnace until the power of the medium frequency furnace returns to zero. At the same time, before pouring the ladle, bake the ladle to 100-200°C in advance. When pouring into the ladle from the medium frequency furnace, introduce argon to protect the pouring process;

[0019] Step 3: Step austenitization: Cool the rough steel blank formed in the ladle in Step 2 until it cools to room temperature, then place the rough steel blank in an industrial furnace for heat treatment, using a stepwise heating method for a period of time;

[0020] Step 4: air cooling quenching, using directional air cooling at a certain wind speed and controlling the cooling rate until lath martensite + 5-8% retained austenite is obtained;

[0021] Step 5: variable temperature tempering: the rough cast steel material processed in step 4 is subjected to a variable temperature heat treatment method for a period of time.

[0022] Preferably, the specific contents of the step-by-step austenitization in step 3 are:

[0023] Step 1: Place the rough cast steel into an industrial furnace and set the initial heat treatment temperature of the industrial furnace to 850°C for 2 hours;

[0024] Step 2: After the step 1, the heat treatment temperature of the industrial furnace is set to 980°C and lasts for 1 hour;

[0025] Step 3: After the processing in step 2, the industrial furnace heat treatment processing temperature is set to 1050° C. and lasts for 0.5 h.

[0026] Preferably, the directional air-cooling quenching in step 4 is specifically as follows: using directional air cooling at a wind speed of 8-12 m / s and controlling the cooling rate to 25-30° C. / s until lath martensite + 5-8% retained austenite is obtained.

[0027] Preferably, the specific steps of temperature-variable tempering in step 5 are:

[0028] Step 1: Set the starting temperature of the variable temperature tempering heat treatment to 260°C and continue for 2 hours;

[0029] Step 2: After step 1, set the starting temperature of the variable temperature tempering heat treatment process temperature to 450°C and continue for 3 hours.

[0030] The technical effects and advantages of the present invention are as follows:

[0031] (1) A hard and tough synergistic layer is formed by C, Cr, Mo and Ni, wherein C can balance hardness and casting fluidity, Cr forms a passivation film, Mo can suppress temper brittleness, Ni improves low-temperature toughness, and B is added to preferentially form a B-Cr compound, which can block the intergranular corrosion channel. Mixed rare earths are used instead of pure rare earths, which greatly reduces costs. The cast steel material made from the above raw materials in percentage by weight not only has good impact wear resistance, but also has good corrosion resistance, while also reducing the cost of raw materials;

[0032] (2) The casting stress can be eliminated by heat treating the cast steel material at 850℃ for 2 hours in an industrial furnace. The carbide can be partially dissolved by heat treating the cast steel material at 980℃ for 1 hour. The cast steel material can be completely austenitized by heat treating the cast steel material at 1050℃ for 0.5 hours. At the same time, the cast steel material can be completely austenitized by heat treating the cast steel material at 260℃ for 2 hours and at 450℃ for 3 hours. The quenching stress can be eliminated by temperature-variable tempering heat treatment. Compared with the traditional single quenching heat treatment, this heat treatment processing method can reduce the residual austenite and improve the dimensional stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the gradient heat treatment preparation method of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The present invention provides a high-hardness, toughness, and wear-resistant cast steel material, comprising the following raw materials in percentage by weight, specifically:

[0036] C 0.35% ~ 0.5%, Cr 14% ~ 16%, Mo 1.8% ~ 2.2%, Ni 0.8% ~ 1.2%, B 0.02% ~ 0.05% and mixed rare earth 0.08% ~ 0.12%.

[0037] Hard-tough synergistic layer: C0.35-0.5% (balance hardness and casting fluidity), Cr14-16% (passivation film formation), Mo1.8-2.2% (suppress temper brittleness), Ni0.8-1.2% (improve low-temperature toughness);

[0038] Intergranular corrosion inhibition: Adding 0.02-0.05% B element preferentially forms B-Cr compounds to block intergranular corrosion channels;

[0039] Low-cost rare earth modification: Use mixed rare earth to replace pure rare earth, with an addition amount of 0.08-0.12%, which reduces costs.

[0040] Furthermore, the mixed rare earth is specifically a mixture of La and Ce, and the weight ratio of La to Ce in the mixture is 3:1.

[0041] Furthermore, the ratio of Cr, Mo and C in the raw material satisfies: (Cr+Mo) / C≥35.

[0042] Furthermore, the cast steel material also includes the following raw materials in percentage by weight, specifically:

[0043] C0.35%, Cr14%, Mo1.8%, Ni0.8%, B0.02% and mixed rare earth 0.08%.

[0044] Furthermore, the cast steel material also includes the following raw materials in percentage by weight, specifically:

[0045] C0.5%, Cr16%, Mo2.2%, Ni1.2%, B0.05% and mixed rare earth 0.12%.

[0046] Furthermore, the cast steel material also includes the following raw materials in percentage by weight, specifically:

[0047] C0.42%, Cr15.2%, Mo2%, Ni1%, B0.03% and mixed rare earth 0.1%.

[0048] The present invention provides Figure 1 A gradient heat treatment preparation method is shown, which implements the high hardness, toughness and wear-resistant cast steel material as described above, and the specific steps of the method are as follows:

[0049] Step 1: Smelting in an intermediate frequency furnace: take out a certain amount of raw materials according to the above weight percentage, and then put them into the intermediate frequency furnace for melting. Set the intermediate frequency furnace melting processing time and the intermediate frequency furnace melting frequency until all the raw materials are completely melted into slurry;

[0050] Step 2: Argon protection pouring: Use the control button to control the medium frequency furnace to slowly reduce the power of the medium frequency furnace until the power of the medium frequency furnace returns to zero. At the same time, before pouring the ladle, bake the ladle to 100-200°C in advance. When pouring into the ladle from the medium frequency furnace, introduce argon to protect the pouring process;

[0051] Step 3: Step austenitization: Cool the rough steel blank formed in the ladle in Step 2 until it cools to room temperature, then place the rough steel blank in an industrial furnace for heat treatment, using a stepwise heating method for a period of time;

[0052] Step 4: air cooling quenching, using directional air cooling at a certain wind speed and controlling the cooling rate until lath martensite + 5-8% retained austenite is obtained;

[0053] Step 5: variable temperature tempering: the rough cast steel material processed in step 4 is subjected to a variable temperature heat treatment method for a period of time.

[0054] Furthermore, the specific contents of the step-by-step austenitization in step 3 are as follows:

[0055] Step 1: Place the rough steel casting into an industrial furnace and set the initial heat treatment temperature of the industrial furnace to 850°C for 2 hours to eliminate casting stress.

[0056] Step 2: After the step 1, the heat treatment temperature of the industrial furnace is set to 980°C and lasts for 1 hour to partially dissolve the carbide;

[0057] Step 3: After the processing in step 2, the industrial furnace heat treatment processing temperature is set to 1050° C. and lasts for 0.5 h for complete austenitization.

[0058] Furthermore, the specific content of the directional air cooling quenching in step 4 is: using directional air cooling with a wind speed of 8-12 m / s and controlling the cooling rate to 25-30° C. / s until lath martensite + 5-8% retained austenite is obtained.

[0059] Furthermore, the specific steps of temperature-variable tempering in step 5 are as follows:

[0060] Step 1: Set the starting temperature of the variable temperature tempering heat treatment to 260°C and continue for 2 hours to eliminate quenching stress;

[0061] Step 2: After the processing in step 1, the starting temperature of the variable temperature tempering heat treatment is set to 450° C. and continued for 3 hours, and finally M7C3 type nanocarbides are precipitated.

[0062] Performance indicators: Hardness: 55-58HRC; Impact toughness: 35-45J / cm 2 (ASTM E23 standard); Corrosion resistance: Corrosion current density in 3.5% NaCl solution ≤ 1×10 -6 A / cm 2 ;Relative wear resistance: 2.5 times higher than high manganese steel (MLD-10 wear testing machine).

[0063] Example 1: Take out the raw materials in percentage by weight, specifically: C0.35%, Cr14%, Mo1.8%, Ni0.8%, B0.02% and mixed rare earth 0.08%, and then put them into the medium frequency furnace for smelting. Set the medium frequency furnace smelting processing time and medium frequency furnace smelting frequency until all the raw materials are completely melted into slurry. Use the control button to control the medium frequency furnace so that the medium frequency furnace slowly reduces the power until the power of the medium frequency furnace returns to zero. At the same time, before pouring the ladle, bake the ladle to 100-200°C in advance. When pouring into the ladle in the medium frequency furnace, introduce argon to protect the pouring process. Cool the rough cast steel material formed in the ladle until the rough cast steel material cools to room temperature. , then the rough cast steel material is placed in an industrial furnace for heat treatment, and the starting heat treatment processing temperature of the industrial furnace is set to 850℃, and it lasts for 2h, then the heat treatment processing temperature of the industrial furnace is set to 980℃, and it lasts for 1h, and then after step two processing, the heat treatment processing temperature of the industrial furnace is set to 1050℃, and it lasts for 0.5h, followed by directional air cooling with a wind speed of 8-12m / s, and the cooling rate is controlled at 25-30℃ / s until lath martensite + 5-8% residual austenite is obtained, and then the starting heat treatment processing temperature of the variable temperature tempering is set to 260℃, and it lasts for 2h, and finally the starting heat treatment processing temperature of the variable temperature tempering is set to 450℃, and it lasts for 3h.

[0064] Example 2: Take out the raw materials in percentage by weight, specifically: C0.5%, Cr16%, Mo2.2%, Ni1.2%, B0.05% and mixed rare earth 0.12%, and then put them into the medium frequency furnace for smelting. Set the medium frequency furnace smelting processing time and medium frequency furnace smelting frequency until all the raw materials are completely melted into slurry. Use the control button to control the medium frequency furnace so that the medium frequency furnace slowly reduces the power until the power of the medium frequency furnace returns to zero. At the same time, before pouring the ladle, bake the ladle to 100-200°C in advance. When pouring into the ladle in the medium frequency furnace, introduce argon to protect the pouring process. Cool the rough cast steel material formed in the ladle until the rough cast steel material cools to room temperature. , then the rough cast steel material is placed in an industrial furnace for heat treatment, and the starting heat treatment processing temperature of the industrial furnace is set to 850℃, and it lasts for 2h, then the heat treatment processing temperature of the industrial furnace is set to 980℃, and it lasts for 1h, and then after step two processing, the heat treatment processing temperature of the industrial furnace is set to 1050℃, and it lasts for 0.5h, followed by directional air cooling with a wind speed of 8-12m / s, and the cooling rate is controlled at 25-30℃ / s until lath martensite + 5-8% residual austenite is obtained, and then the starting heat treatment processing temperature of the variable temperature tempering is set to 260℃, and it lasts for 2h, and finally the starting heat treatment processing temperature of the variable temperature tempering is set to 450℃, and it lasts for 3h.

[0065] Example 3: Take out the raw materials in percentage by weight, specifically: C0.42%, Cr15.2%, Mo2%, Ni1%, B0.03% and mixed rare earth 0.1%, and Fe balance, and then put them into the medium frequency furnace for smelting, set the medium frequency furnace smelting processing time and medium frequency furnace smelting frequency, until all the raw materials are completely melted into slurry, use the control button to control the medium frequency furnace, so that the medium frequency furnace slowly reduces the power, and until the power of the medium frequency furnace returns to zero, and at the same time, before pouring the ladle, bake the ladle to 100-200°C in advance, when pouring into the ladle in the medium frequency furnace, introduce argon to protect the pouring process, cool the rough cast steel material formed in the ladle until the rough cast steel material cools to room temperature, and then The rough cast steel material is placed in an industrial furnace for heat treatment, and the starting heat treatment processing temperature of the industrial furnace is set to 850°C and continued for 2 hours, then the heat treatment processing temperature of the industrial furnace is set to 980°C and continued for 1 hour, and then after processing in step two, the heat treatment processing temperature of the industrial furnace is set to 1050°C and continued for 0.5 hours, followed by directional air cooling with a wind speed of 8-12m / s, and the cooling rate is controlled at 25-30°C / s until lath martensite + 5-8% residual austenite is obtained, and then the starting heat treatment processing temperature of the variable temperature tempering is set to 260°C and continued for 2 hours, and finally the starting heat treatment processing temperature of the variable temperature tempering is set to 450°C and continued for 3 hours, to obtain cast steel for mine lining.

[0066] The performance indicators of the cast steel material processed in Example 3 are: hardness 57HRC, impact toughness 42J / cm 2 ; In acidic slurry with pH=3, the wear amount is reduced by 60% compared with high chromium cast iron.

[0067] Comparative Example

[0068] Comparative Group 1 (no B element added): The intergranular corrosion rate of the cast steel material made from the raw materials increased by 3 times according to the weight percentage;

[0069] Comparative Group 2 (conventional oil quenching): The retained austenite of the cast steel material processed by traditional oil quenching heat treatment reached 12%, and the dimensional deformation exceeded the tolerance by 0.5 mm.

[0070] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high hardness, toughness and wear-resistant cast steel material, characterized in that: The invention comprises the following raw materials in percentage by weight, specifically: C 0.35% ~ 0.5%, Cr 14% ~ 16%, Mo 1.8% ~ 2.2%, Ni 0.8% ~ 1.2%, B 0.02% ~ 0.05% and mixed rare earth 0.08% ~ 0.12%.

2. The high hardness, toughness and wear-resistant cast steel material according to claim 1, characterized in that: The mixed rare earth is specifically a mixture of La and Ce, and the weight ratio of La to Ce in the mixture is 3:

1.

3. The high hardness, toughness and wear-resistant cast steel material according to claim 1, characterized in that: The ratio of Cr, Mo and C in the raw material satisfies: (Cr+Mo) / C≥35.

4. The high hardness, toughness and wear-resistant cast steel material according to claim 3, characterized in that: The cast steel material further comprises the following raw materials in percentage by weight, specifically: C0.35%, Cr14%, Mo1.8%, Ni0.8%, B0.02% and mixed rare earth 0.08%.

5. The high hardness, toughness and wear-resistant cast steel material according to claim 3, characterized in that: The cast steel material further comprises the following raw materials in percentage by weight, specifically: C0.5%, Cr16%, Mo2.2%, Ni1.2%, B0.05% and mixed rare earth 0.12%.

6. The high hardness, toughness and wear-resistant cast steel material according to claim 1, characterized in that: The cast steel material further comprises the following raw materials in percentage by weight, specifically: C0.42%, Cr15.2%, Mo2%, Ni1%, B0.03% and mixed rare earth 0.1%.

7. A gradient heat treatment preparation method, which implements the high hardness, toughness and wear-resistant cast steel material according to any one of claims 1 to 6, characterized in that: The specific steps of the method are as follows: Step 1: Smelting in an intermediate frequency furnace: take out a certain amount of raw materials according to the above weight percentage, and then put them into the intermediate frequency furnace for melting. Set the intermediate frequency furnace melting processing time and the intermediate frequency furnace melting frequency until all the raw materials are completely melted into slurry; Step 2: Argon protection pouring: Use the control button to control the medium frequency furnace to slowly reduce the power of the medium frequency furnace until the power of the medium frequency furnace returns to zero. At the same time, before pouring the ladle, bake the ladle to 100-200°C in advance. When pouring into the ladle from the medium frequency furnace, introduce argon to protect the pouring process; Step 3: Step austenitization: Cool the rough steel blank formed in the ladle in Step 2 until it cools to room temperature, then place the rough steel blank in an industrial furnace for heat treatment, using a stepwise heating method for a period of time; Step 4: air cooling quenching, using directional air cooling at a certain wind speed and controlling the cooling rate until lath martensite + 5-8% retained austenite is obtained; Step 5: variable temperature tempering: the rough cast steel material processed in step 4 is subjected to a variable temperature heat treatment method for a period of time.

8. A gradient heat treatment preparation method according to claim 7, characterized in that: The specific contents of the step-by-step austenitization in step 3 are as follows: Step 1: Place the rough cast steel into an industrial furnace and set the initial heat treatment temperature of the industrial furnace to 850°C for 2 hours; Step 2: After the step 1, the heat treatment temperature of the industrial furnace is set to 980°C and lasts for 1 hour; Step 3: After the processing in step 2, the industrial furnace heat treatment processing temperature is set to 1050° C. and lasts for 0.5 h.

9. A gradient heat treatment preparation method according to claim 7, characterized in that: The specific content of the directional air cooling quenching in step 4 is: using directional air cooling with a wind speed of 8-12 m / s and controlling the cooling rate to 25-30° C. / s until lath martensite + 5-8% retained austenite is obtained.

10. A gradient heat treatment preparation method according to claim 7, characterized in that: The specific steps of temperature-variable tempering in step 5 are: Step 1: Set the starting temperature of the variable temperature tempering heat treatment to 260°C and continue for 2 hours; Step 2: After step 1, set the starting temperature of the variable temperature tempering heat treatment process temperature to 450°C and continue for 3 hours.

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