Low-temperature-resistant weldable cast steel material as well as preparation process and application thereof

Abstract

The invention relates to the technical field of cast steel material preparation, in particular to a low-temperature-resistant weldable cast steel material and a preparation technology and application thereof.The low-temperature-resistant weldable cast steel material comprises, by mass, 0.1%-0.21% of C, 0.4%-0.8% of Si, 0.9%-1.3% of Mn, 0.5%-0.8% of Ni, 0.02%-0.06% of Al, smaller than or equal to 0.3% of Cr, smaller than or equal to 0.2% of Mo and the balance Fe and inevitable impurities. By optimizing the material composition proportion and matching with preparation process control, the provided cast steel material has good low-temperature impact toughness at the low temperature of-50 DEG C and also has excellent welding performance, and the requirements under extremely cold, high-impact and heavy-load working conditions are met.

Description

Technical Field

[0001] The invention relates to the technical field of cast steel material preparation, in particular to a low-temperature resistant weldable cast steel material and a preparation process and application thereof. Background Art

[0002] The low-temperature weldable steel casting industry for construction machinery has huge development potential and economic benefits. According to statistics from the Russian Machinery Manufacturing Association, imports of low-temperature weldable steel castings for construction machinery increased by 58% in 2023, exceeding 440 billion rubles, almost five times the output of Russia. Russia is a country rich in resources such as coal, gold, tin, and diamonds. Mining requires large loaders, excavators, bulldozers, mining trucks and other construction machinery products. Russia has a vast territory, 36% of which is located within the Arctic Circle. The average temperature in January reaches -50°C, and the lowest temperature is about -70°C. However, large-scale construction machinery structural parts use a large number of cast steel parts. Generally, cast steel parts only meet the requirements of impact toughness at room temperature. They are prone to ductile-brittle transition in low-temperature environments, which leads to brittle fracture of the entire structural part, bringing major safety hazards and property losses. Generally, structural parts are welded by cast steel parts and plate parts, and require good weldability. However, the current steel castings in the field generally cannot meet the requirements of weldability and low temperature resistance (≤-50°C) at the same time. For example, a Chinese patent (authorization announcement number CN 112695245B) discloses a low-temperature steel for drilling rigs in extremely cold areas and its heat treatment process. The normal operation requirements in a low-temperature environment of -40°C are met by designing and optimizing the material composition ratio and reasonably selecting the smelting and heat treatment processes. However, when the operating temperature is further reduced, the material cannot meet the requirements. A Chinese patent (authorization announcement number CN 115717218 B) discloses a low-temperature resistant oil well pipe steel for extremely cold environments and its preparation method. The existing low-temperature oil well pipe steel usually has a high Ni content and high cost by optimizing the material ratio, but it cannot ensure low-temperature resistance on the basis of ensuring good weldability. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a low-temperature resistant and weldable cast steel material. By optimizing the material composition ratio and coordinating the preparation process control, the provided cast steel material has good low-temperature impact toughness at -50°C and excellent welding performance, meeting the requirements of extremely cold, high impact and heavy load working conditions.

[0004] On the one hand, the present invention provides a low-temperature resistant weldable cast steel material, wherein the components of the low-temperature resistant weldable cast steel material include, by mass percentage: C: 0.1% to 0.21%, Si: 0.4% to 0.8%, Mn: 0.9% to 1.3%, Ni: 0.5% to 0.8%, Al: 0.02% to 0.06%, Cr: ≤0.3%, Mo≤0.2%, and the remainder is Fe and unavoidable impurities.

[0005] As a preferred technical solution, among the inevitable impurities, at least P: ≤ 0.03% and S: ≤ 0.02% are controlled.

[0006] Preferably, among the inevitable impurities, at least P is controlled to be ≤0.02% and S to be ≤0.017%.

[0007] As a preferred technical solution, the carbon equivalent of the low-temperature resistant weldable cast steel material (Ceq=C+Mn / 6+(Cr+V+Mo) / 5+(Cu+Ni) / 15) is ≤0.45%.

[0008] Preferably, the carbon equivalent of the low-temperature resistant weldable cast steel material is 0.37-0.45%.

[0009] As an example, the carbon equivalent of the low-temperature resistant weldable cast steel material is 0.39, 0.40, 0.41, 0.42, or 0.43.

[0010] As a preferred technical solution, the microstructure of the low-temperature resistant weldable cast steel material is tempered troostite + a small amount of ferrite, wherein the phase ratio of tempered troostite is 90% to 100%, and the phase ratio of ferrite is 0 to 10%.

[0011] As a preferred technical solution, the mass proportion of C in the low-temperature resistant weldable cast steel material is 0.16% to 0.19%.

[0012] As an example, the mass proportion of C in the low-temperature resistant weldable cast steel material is 0.16%, 0.17%, 0.18%, and 0.19%.

[0013] As a preferred technical solution, the mass ratio of Mn to C (Mn / C) in the low-temperature resistant weldable cast steel material is (4-8):1.

[0014] As an example, the mass ratio of Mn to C (Mn / C) in the low-temperature resistant weldable cast steel material is 4:1, 4.7:1, 5:1, 5.6:1, 6:1, 6.3:1, 7:1, and 8:1.

[0015] As a preferred technical solution, the mass proportion of Al in the low-temperature resistant weldable cast steel material is 0.02% to 0.046%.

[0016] As an example, the mass proportion of Al in the low-temperature resistant weldable cast steel material is 0.02%, 0.24%, 0.03% and 0.46%.

[0017] As a preferred technical solution, the mass proportion of Si in the low-temperature resistant weldable cast steel material is 0.48% to 0.5%.

[0018] As an example, the mass proportion of Si in the low-temperature resistant weldable cast steel material is 0.48%, 0.49% and 0.5%.

[0019] As a preferred technical solution, the mass proportion of Cr in the low-temperature resistant weldable cast steel material is ≤0.07%.

[0020] As a preferred technical solution, the mass proportion of Ni in the low-temperature resistant weldable cast steel material is 0.6% to 0.73%.

[0021] As an example, the mass proportion of Ni in the low-temperature resistant weldable cast steel material is 0.6%, 0.62%, 0.65%, 0.7%, 0.72%, and 0.73%.

[0022] As a preferred technical solution, the mass proportion of Mo in the low-temperature resistant weldable cast steel material is ≤0.01%.

[0023] The present invention optimizes the content of each element in the cast steel material to make the carbon equivalent of the low-temperature resistant weldable cast steel material 0.37-0.45%, cooperates with the preparation process, ensures the low-temperature resistance of the cast steel material while balancing the welding performance of the cast steel material, so that the provided product is more suitable for high-cold areas, -42 ° C impact energy Akv ≥ 100J; at a higher temperature (500 ° C) with higher strength: σb ≥ 450MPa, σ0.2 ≥ 320MPa. Specifically, the present invention found in the process of exploration that by optimizing the mass proportion of C in the low-temperature resistant weldable cast steel material to 0.16% to 0.19%, and controlling the mass ratio of Mn and C (Mn / C) to (4-8): 1, the microstructure of tempered troostite + ferrite is formed, and the weldability, toughness, strength and hardness of the cast steel material are balanced. However, if the C content is too high and the Mn / C is too low, the welding performance is reduced, the toughness is reduced, and if the C content is too low and the Mn / C is too high, the strength and hardness are reduced, which cannot meet the actual application requirements.

[0024] Furthermore, by controlling the mass proportion of Al in the low-temperature resistant weldable cast steel material to 0.04%-0.06%, the mass proportion of Si to 0.48%-0.5%, the mass proportion of Ni to 0.6%-0.73%, and the mass proportion of Mo to ≤0.01%, the welding performance and low-temperature toughness of the product can be further improved while ensuring low costs. Too high a content of Al can not only increase costs, but also cause the weldability of the product to deteriorate, and it is impossible to effectively balance toughness and strength.

[0025] In addition, among the inevitable impurities, at least P: ≤ 0.03%, S: ≤ 0.02%, especially at least P: ≤ 0.02%, S: ≤ 0.017%, to reduce the adverse effects of inevitable impurities on welding performance and toughness and ensure the service life of the cast steel material.

[0026] As a preferred technical solution, the performance of the low temperature resistant weldable cast steel material meets the following requirements:

[0027] A. Yield strength ≥450N / mm 2 ;

[0028] B. Tensile strength ≥550N / mm 2 ;

[0029] C. Elongation ≥ 18%;

[0030] D. Impact absorption energy at least 50J at -50℃;

[0031] E. Hardness ≥175.

[0032] Another aspect of the present invention provides a process for preparing a low temperature resistant weldable cast steel material, comprising at least the following steps:

[0033] S1, smelting and casting;

[0034] S2, normalizing;

[0035] S3. Tempering.

[0036] As a preferred technical solution, the smelting in step S1 is specifically as follows: adding the cast steel material into a furnace for smelting at a smelting temperature of 1610-1650° C. for a smelting time of 1.5-2.5 h, and adding at least a strong deoxidizer during the deoxidation operation when tapping the steel.

[0037] As a preferred technical solution, the strong deoxidizer is aluminum.

[0038] As a preferred technical solution, in addition to adding a strong deoxidizer during the deoxidation process during steel tapping, rare earth ferrosilicon alloy is also added. Preferably, the amount of rare earth ferrosilicon alloy added is 0.1% to 0.3% of the mass of the steel tapping, preferably 0.15% to 0.25%.

[0039] As a preferred technical solution, the casting in step S1 specifically includes: obtaining a steel casting by sand casting, wherein the casting sand on the surface of the steel casting is chromite sand.

[0040] As a preferred technical solution, the normalizing step S2 is specifically as follows: heating the steel casting from 15-35°C to 880-1000°C at a heating rate of 140-160°C / h, and keeping the temperature at this temperature for 3-5h.

[0041] As a preferred technical solution, the S3 quenching and tempering is specifically as follows: heating the steel casting to 880-900°C, keeping it warm for 3.5-4 hours, quenching, heating it to 580-620°C for tempering, and keeping it warm for 4-5 hours.

[0042] The invention optimizes the preparation process, especially controls the addition of strong deoxidizer aluminum during the deoxidation operation when tapping, and also adds 0.15%-0.25% of rare earth ferrosilicon alloy to improve the cleanliness of molten steel, reduce the oxygen content and slag inclusion rate, and the particles of oxide inclusions are relatively fine, and the distribution is relatively dispersed and uniform. At the same time, the grain boundary is purified, the ductility and toughness are improved, the content of harmful residual elements in the cast steel material is low, and the service life, stability and reliability of the casting are excellent. Further, sand casting is adopted, and chromite sand is used to accelerate the cold shock effect, accelerate the solidification speed, refine the grains, and obtain a good cast structure, the cast structure is a lamellar pearlite structure, and the casting structure is fine and uniform.

[0043] Beneficial Effects

[0044] 1. The present invention provides a low-temperature resistant weldable cast steel material. By optimizing the material composition ratio and coordinating the preparation process control, the provided cast steel material has good low-temperature impact toughness at -50°C and excellent welding performance, meeting the requirements of extremely cold, high impact and heavy load working conditions.

[0045] 2. The present invention optimizes the content of each element in the cast steel material to make the carbon equivalent of the low-temperature resistant weldable cast steel material 0.37-0.45%, and cooperates with the preparation process to ensure the low-temperature resistance of the cast steel material while balancing the welding performance of the cast steel material, so that the provided product is more suitable for high-cold areas, with an impact energy Akv ≥ 100J at -42°C; and has higher strength at a higher temperature (500°C): σb ≥ 450MPa, σ0.2 ≥ 320MPa.

[0046] 3. The present invention optimizes the mass proportion of C in the low-temperature resistant weldable cast steel material to 0.16% to 0.19%, and controls the mass ratio of Mn and C (Mn / C) to (4-8):1, thereby promoting the formation of a microstructure of tempered troostite + ferrite and balancing the weldability, toughness, strength and hardness of the cast steel material.

[0047] 4. The present invention further improves the welding performance and low-temperature toughness of the product while ensuring low cost by controlling the mass proportion of Al in the low-temperature resistant weldable cast steel material to 0.04% to 0.06%, the mass proportion of Si to 0.48% to 0.5%, the mass proportion of Ni to 0.6% to 0.73%, and the mass proportion of Mo to ≤0.01%.

[0048] 5. The present invention optimizes the preparation process, especially controls the addition of strong deoxidizer aluminum during the deoxidation operation when tapping, and also adds 0.15%-0.25% of rare earth ferrosilicon alloy to improve the cleanliness of molten steel, reduce the oxygen content and slag inclusion rate, and the particles of oxide inclusions are relatively fine, and the distribution is relatively dispersed and uniform. At the same time, the grain boundaries are purified, the ductility and toughness are improved, the content of harmful residual elements in the cast steel material is low, and the service life, stability and reliability of the casting are excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is the microstructure diagram of the low-temperature resistant weldable cast steel material provided in Example 1.

[0050] Figure 2 This is the microstructure diagram of the low-temperature resistant weldable cast steel material provided in Example 2.

[0051] Figure 3 This is the microstructure diagram of the low-temperature resistant weldable cast steel material provided in Example 3.

[0052] Figure 4 This is the microstructure diagram of the low-temperature resistant weldable cast steel material provided in Example 4.

[0053] Figure 5 This is the microstructure diagram of the low-temperature resistant weldable cast steel material provided in Example 5. DETAILED DESCRIPTION

[0054] Examples 1-5

[0055] Embodiments 1-5 of the present invention provide a low temperature resistant weldable cast steel material. The components of the low temperature resistant weldable cast steel material are shown in Table 1 by mass percentage, and the remainder is iron and other inevitable impurities.

[0056] Table 1

[0057]

[0058] Note: “ / ” in Table 1 means the content of the corresponding element is 0.

[0059] On the other hand, embodiments 1-3 of the present invention provide a preparation process of a low temperature resistant weldable cast steel material, comprising the following steps:

[0060] S1, smelting and casting;

[0061] S2, normalizing;

[0062] S3. Tempering.

[0063] The smelting in step S1 is specifically as follows: adding the cast steel material into a furnace for smelting at a smelting temperature of 1650°C for a smelting time of 2 hours, adding a strong deoxidizer during the deoxidation operation when tapping, and adding a rare earth ferrosilicon alloy in addition to the strong deoxidizer during the deoxidation operation when tapping, wherein the rare earth ferrosilicon alloy is "GB / T 4137 Rare Earth Ferrosilicon Alloy" grade 195023, and the addition amount is 0.25% of the mass of the tapped steel. The strong deoxidizer is aluminum.

[0064] The casting in step S1 specifically includes: obtaining a steel casting by using sand casting, wherein the casting sand on the surface of the steel casting is chromite sand.

[0065] The normalizing step S2 specifically includes heating the steel casting from 25° C. to 90° C. at a heating rate of 150° C. / h, and keeping the temperature at this temperature for 4 hours.

[0066] The S3 quenching and tempering is specifically as follows: heating the steel casting to 900°C, keeping it warm for 4 hours, quenching, heating it to 600°C for tempering, and keeping it warm for 4 hours.

[0067] On the other hand, Embodiment 4-5 of the present invention provides a preparation process of a low temperature resistant weldable cast steel material, comprising the following steps:

[0068] S1, smelting and casting;

[0069] S2, normalizing;

[0070] S3. Tempering.

[0071] The smelting in step S1 is specifically as follows: adding the cast steel material into a furnace for smelting at a smelting temperature of 1650° C. for a smelting time of 2 hours, and adding a strong deoxidizer during the deoxidation operation when tapping the steel.

[0072] The casting in step S1 specifically includes: obtaining a steel casting by using sand casting, wherein the casting sand on the surface of the steel casting is chromite sand.

[0073] The normalizing step S2 is specifically as follows: heating the steel casting from room temperature to 900° C. at a heating rate of 150° C. / h, and keeping the temperature at this temperature for 4 hours.

[0074] The S3 quenching and tempering is specifically as follows: heating the steel casting to 900°C, keeping it warm for 4 hours, quenching, heating it to 620°C and tempering it, and keeping it warm for 4 hours.

[0075] Performance Testing

[0076] 1. The microstructure of the low temperature resistant weldable cast steel material provided in Examples 1-5 is shown in Table 1. Figure 1-5 .

[0077] 2. The yield strength, tensile strength, elongation, impact absorption energy and hardness of the low-temperature resistant weldable cast steel materials provided in Examples 1-5 were tested. The test method is as follows. The test results are shown in Table 2.

[0078] (1) Yield strength: GB / T 228.1 Tensile tests on metallic materials Part 1: Room temperature test methods.

[0079] (2) Tensile strength: GB / T 228.1 Tensile tests on metallic materials - Part 1: Room temperature test method.

[0080] (3) Elongation: GB / T 228.1 Tensile tests on metallic materials - Part 1: Room temperature test methods.

[0081] (4) Impact absorption energy: GB / T 229 Charpy pendulum impact test method for metallic materials.

[0082] (5) Hardness: GB / T 231.1 Metallic materials Brinell hardness test Part 1 Test method.

[0083] Table 2

[0084]

[0085]

Claims

1. A low temperature resistant weldable cast steel material, characterized in that: The components of the low-temperature resistant weldable cast steel material include, by mass percentage, C: 0.1% to 0.21%, Si: 0.4% to 0.8%, Mn: 0.9% to 1.3%, Ni: 0.5% to 0.8%, Al: 0.02% to 0.06%, Cr: ≤0.3%, Mo≤0.2%, and the remainder is Fe and unavoidable impurities.

2. The low temperature resistant weldable cast steel material according to claim 1, characterized in that: Among the inevitable impurities, at least P: ≤ 0.03% and S: ≤ 0.02%.

3. The low temperature resistant weldable cast steel material according to claim 2, characterized in that: The carbon equivalent of the low temperature resistant weldable cast steel material is ≤0.45%.

4. The low temperature resistant weldable cast steel material according to claim 2, characterized in that: The mass proportion of C in the low-temperature resistant weldable cast steel material is 0.16% to 0.19%.

5. The low temperature resistant weldable cast steel material according to claim 4, characterized in that: The mass ratio of Mn to C in the low-temperature resistant weldable cast steel material is (4-8):

1.

6. The low temperature resistant weldable cast steel material according to claim 5, characterized in that: The properties of the low temperature resistant weldable cast steel material meet the following requirements: A. Yield strength ≥450N / mm 2 ; B. Tensile strength ≥550N / mm 2 ; C. Elongation ≥ 18%; D. Impact absorption energy at least 50J at -50℃; E. Hardness ≥175.

7. A process for preparing a low temperature resistant weldable cast steel material according to any one of claims 1 to 6, characterized in that: At least the following steps are included: S1, smelting and casting; S2, normalizing; S3. Tempering.

8. The process for preparing the low temperature resistant weldable cast steel material according to claim 7, characterized in that: The smelting in step S1 is specifically as follows: adding the cast steel material into a furnace for smelting at a smelting temperature of 1610-1650° C. for a smelting time of 1.5-2.5 hours, and at least adding a strong deoxidizer during the deoxidation operation when tapping the steel.

9. The process for preparing the low temperature resistant weldable cast steel material according to claim 8, characterized in that: In the steel tapping process, in addition to adding a strong deoxidizer, a rare earth ferrosilicon alloy is also added during the deoxidation operation.

10. The process for preparing low temperature resistant weldable cast steel material according to claim 9, characterized in that: The casting in step S1 specifically includes: obtaining a steel casting by using sand casting, wherein the casting sand on the surface of the steel casting is chromite sand.

Images