Production process of LCC steel with excellent low-temperature impact toughness

Abstract

The invention discloses a production process of LCC steel with excellent low-temperature impact toughness. The production process comprises the following steps: A, chemical component optimization: the content of C is 0.05%-0.08%, the content of Mn is 0.30%-0.60%, the content of Si is 0.20%-0.40%, the content of Cr is 0.05%-0.15%, the content of Mo is 0.10%-0.30%, the content of Ni is 0.05%-0.10%, and the content of Cu is 0.05%-0.10%; b, smelting process: smelting by adopting an electric furnace and removing impurities in molten steel through vacuum degassing; c, casting process: controlling the temperature of the casting mould to be 1450-1550 DEG C in the casting process, and adopting a low-temperature slow cooling method; d, a heat treatment process: firstly carrying out normalizing treatment at the temperature of 850-900 DEG C, and keeping the temperature for 1-2 hours; then low-temperature tempering is conducted, the temperature ranges from 400 DEG C to 450 DEG C, and heat preservation is conducted for 1-2 hours; surface polishing treatment is conducted on the formed steel, ultrasonic flaw detection or X-ray detection is conducted, and the internal quality of the steel is ensured, the low-temperature impact toughness of the steel can be improved, the steel can still keep good toughness in the low-temperature environment, and brittle fracture is avoided.

Description

Technical Field

[0001] The invention relates to the field of LCC steel production technology, and in particular to a production technology of LCC steel with excellent low-temperature impact toughness. Background Art

[0002] LCC steel (Low Carbon Cast Steel) has good casting performance and mechanical properties and is widely used in structural parts in low temperature environments.

[0003] However, conventional LCC steel has poor impact toughness under low temperature conditions and is prone to brittle fracture, which cannot meet the performance requirements of some high-demand applications. In order to improve the low-temperature impact toughness of LCC steel, it is usually necessary to optimize the organizational structure of the steel by adjusting its chemical composition, smelting process and heat treatment process, but the existing technology still has problems such as unstable optimization effect and high cost.

[0004] Therefore, how to improve the low temperature impact toughness of LCC steel while ensuring its other properties has become an urgent problem to be solved in the field of steel metallurgy. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the above-mentioned technology at least to some extent.

[0006] To achieve the above object, the present invention provides a production process of LCC steel with excellent low temperature impact toughness, comprising:

[0007] A. Chemical composition optimization: C content is 0.05% to 0.08%, Mn content is 0.30% to 0.60%, Si content is 0.20% to 0.40%, Cr content is 0.05% to 0.15%, Mo content is 0.10% to 0.30%, Ni content is 0.05% to 0.10%, and Cu content is 0.05% to 0.10%;

[0008] B. Smelting process: Electric furnace smelting and vacuum degassing are used to remove impurities in the molten steel to ensure the uniformity and high purity of the molten steel;

[0009] C. Casting process: During the casting process, the mold temperature is controlled at 1450℃~1550℃, and a low-temperature slow cooling method is adopted to reduce cooling stress and improve the microstructure uniformity of the steel;

[0010] D. Heat treatment process: firstly, normalizing treatment is carried out at a temperature of 850℃~900℃, and the temperature is kept at that for 1~2 hours; then low-temperature tempering is carried out at a temperature of 400℃~450℃, and the temperature is kept at that for 1~2 hours;

[0011] E. Post-processing process: Polish the surface of the formed steel to eliminate surface defects, and use ultrasonic testing or X-ray testing to ensure the internal quality of the steel.

[0012] In addition, the production process of the LCC steel with excellent low temperature impact toughness proposed in the present invention may also have the following additional technical features:

[0013] Furthermore, the chemical composition has a Mn content of 0.45% to 0.55%, a Si content of 0.25% to 0.35%, a Cr content of 0.08% to 0.12%, a Mo content of 0.15% to 0.20%, a Ni content of 0.06% to 0.09%, and a Cu content of 0.06% to 0.09%.

[0014] Furthermore, the low-temperature slow cooling method in the casting process includes controlling the cooling rate of the casting so that the surface cooling rate of the casting is 10°C / min to 20°C / min and the internal cooling rate is 5°C / min to 10°C / min.

[0015] Furthermore, the low temperature impact toughness test of the steel is a Charpy impact test carried out at -40°C.

[0016] Furthermore, the temperature of the normalizing treatment is 870° C., the temperature of the tempering treatment is 420° C., and the holding time is 1 hour.

[0017] Furthermore, the surface polishing treatment includes using mechanical polishing, sandblasting or grinding technology to remove surface defects of the steel.

[0018] Furthermore, the low-temperature impact toughness of the steel is improved by at least 30%, and in an impact test at -40°C, the Charpy impact value reaches above 35J.

[0019] Furthermore, the heat treatment step further includes performing surface oxidation treatment after tempering to enhance the corrosion resistance of the steel.

[0020] Furthermore, the steel is suitable for use in low temperature environments, and is particularly suitable for use as structural materials for low temperature containers, refrigeration equipment, pipelines, ships, and the like.

[0021] Furthermore, the process significantly improves the low-temperature impact toughness of LCC steel by optimizing the chemical composition, smelting process, casting process, heat treatment process and post-surface treatment, and ensures its stable mechanical properties, making it suitable for high-demand low-temperature applications.

[0022] According to the production process of LCC steel with excellent low-temperature impact toughness of the present invention, the low-temperature impact toughness of the steel can be significantly improved by optimizing the chemical composition and smelting process of the LCC steel, so that it can still maintain good toughness in a low-temperature environment and avoid the occurrence of brittle fracture. The casting process and heat treatment process adopted can further refine the grains of the steel and improve its microstructure, thereby improving the impact toughness and mechanical properties and ensuring the stability of the steel in harsh working environments. The production process technology of the present invention is mature and cost-controllable, and can significantly improve the low-temperature impact performance of LCC steel without significantly increasing production costs, and has good industrial application prospects.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, examples of which are shown in the scheme, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by reference to the scheme are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0025] The following describes the production process of LCC steel with excellent low-temperature impact toughness according to an embodiment of the present invention in combination with the scheme.

[0026] The production process of the LCC steel with excellent low-temperature impact toughness according to the embodiment of the present invention may include:

[0027] A. Chemical composition optimization: C content is 0.05%~0.08%, Mn content is 0.30%~0.60%, Si content is 0.20%~0.40%, Cr content is 0.05%~0.15%, Mo content is 0.10%~0.30%, Ni content is 0.05%~0.10%, and Cu content is 0.05%~0.10%.

[0028] The chemical composition has a Mn content of 0.45% to 0.55%, a Si content of 0.25% to 0.35%, a Cr content of 0.08% to 0.12%, a Mo content of 0.15% to 0.20%, a Ni content of 0.06% to 0.09%, and a Cu content of 0.06% to 0.09%.

[0029] By precisely controlling the chemical composition of steel, especially the ratio of trace elements (such as Mn, Si, Cr, Mo, etc.), the low-temperature impact toughness of LCC steel can be effectively improved. The optimized composition enables the steel to maintain good plasticity and toughness at low temperatures and avoid brittle fracture.

[0030] Smelting process: Electric furnace smelting and vacuum degassing are used to remove impurities in the molten steel to ensure the uniformity and high purity of the molten steel.

[0031] Using electric furnace smelting and vacuum degassing to remove impurities in molten steel not only improves the purity of molten steel, but also ensures the uniformity of steel, which is crucial to the performance stability of the final product. Higher purity helps improve the mechanical properties and resistance to low-temperature brittleness of steel.

[0032] C. Casting process: During the casting process, the mold temperature is controlled at 1450℃~1550℃, and a low-temperature slow cooling method is adopted to reduce cooling stress and improve the microstructure uniformity of the steel.

[0033] The low-temperature slow cooling method in the casting process includes controlling the cooling rate of the casting so that the surface cooling rate of the casting is 10°C / min to 20°C / min and the internal cooling rate is 5°C / min to 10°C / min.

[0034] Controlling the mold temperature during the casting process and adopting a low-temperature slow cooling method can effectively reduce cooling stress, promote the homogenization of the internal structure of the steel, avoid internal defects and microcracks caused by uneven cooling, and thus improve the overall strength and toughness of the steel.

[0035] D. Heat treatment process: First, normalizing treatment is carried out at a temperature of 850℃~900℃, and the temperature is kept for 1~2 hours; then low-temperature tempering is carried out at a temperature of 400℃~450℃, and the temperature is kept for 1~2 hours.

[0036] The temperature of the normalizing treatment is 870° C., the temperature of the tempering treatment is 420° C., and the holding time is 1 hour.

[0037] The heat treatment step further includes performing a surface oxidation treatment after tempering to enhance the corrosion resistance of the steel.

[0038] Through reasonable normalizing and low temperature tempering process, the microstructure of steel is optimized, the brittleness of steel is reduced, and its impact toughness in low temperature environment is enhanced. In particular, post-treatment after tempering can effectively reduce the hardness and improve the ductility of steel.

[0039] E. Post-processing process: Polish the surface of the formed steel to eliminate surface defects, and use ultrasonic testing or X-ray testing to ensure the internal quality of the steel.

[0040] The surface polishing treatment includes adopting mechanical polishing, sandblasting or grinding process to remove the surface defects of steel.

[0041] Mechanical polishing, sandblasting or grinding processes are used to remove surface defects that may affect the performance of steel, thereby ensuring the surface quality of steel. At the same time, ultrasonic flaw detection and X-ray testing further ensure the internal quality of steel and improve product reliability.

[0042] The low temperature impact toughness test of the steel is a Charpy impact test carried out at -40°C.

[0043] The low-temperature impact toughness of the steel is improved by at least 30%, and in an impact test at -40°C, the Charpy impact value reaches more than 35J.

[0044] Through the above process optimization, the low-temperature impact toughness of the finished LCC steel has been significantly improved. Especially in the Charpy impact test at -40°C, the impact toughness of the steel has been improved by at least 30%, and the Charpy impact value has reached more than 35J, far exceeding the low-temperature toughness requirements of ordinary steel.

[0045] The steel is suitable for use in low temperature environments, and is particularly suitable for use as structural materials for low temperature containers, refrigeration equipment, pipelines, ships, and the like.

[0046] The above process significantly improves the low-temperature impact toughness of LCC steel by optimizing the chemical composition, smelting process, casting process, heat treatment process and post-surface treatment, and ensures its stable mechanical properties, making it suitable for high-demand low-temperature applications.

[0047] The LCC steel treated by this process not only has excellent low-temperature impact toughness, but also has good mechanical property stability. It can adapt to more harsh low-temperature environments and is suitable for structural materials such as low-temperature containers, refrigeration equipment, pipelines, ships, etc., especially in low-temperature applications with higher requirements.

[0048] In summary, the production process of LCC steel with excellent low-temperature impact toughness according to the embodiment of the present invention can improve the low-temperature impact toughness of the steel, so that it can still maintain good toughness in a low-temperature environment and avoid the occurrence of brittle fracture.

[0049] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0051] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A production process for LCC steel with excellent low temperature impact toughness, characterized in that: include: A. Chemical composition optimization: C content is 0.05% to 0.08%, Mn content is 0.30% to 0.60%, Si content is 0.20% to 0.40%, Cr content is 0.05% to 0.15%, Mo content is 0.10% to 0.30%, Ni content is 0.05% to 0.10%, and Cu content is 0.05% to 0.10%; B. Smelting process: Electric furnace smelting and vacuum degassing are used to remove impurities in the molten steel to ensure the uniformity and high purity of the molten steel; C. Casting process: During the casting process, the mold temperature is controlled at 1450℃~1550℃, and a low-temperature slow cooling method is adopted to reduce cooling stress and improve the microstructure uniformity of the steel; D. Heat treatment process: firstly, normalizing treatment is carried out at a temperature of 850℃~900℃, and the temperature is kept at that for 1~2 hours; then low-temperature tempering is carried out at a temperature of 400℃~450℃, and the temperature is kept at that for 1~2 hours; E. Post-processing process: Polish the surface of the formed steel to eliminate surface defects, and use ultrasonic testing or X-ray testing to ensure the internal quality of the steel.

2. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The chemical composition has a Mn content of 0.45% to 0.55%, a Si content of 0.25% to 0.35%, a Cr content of 0.08% to 0.12%, a Mo content of 0.15% to 0.20%, a Ni content of 0.06% to 0.09%, and a Cu content of 0.06% to 0.09%.

3. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The low-temperature slow cooling method in the casting process includes controlling the cooling rate of the casting so that the surface cooling rate of the casting is 10°C / min to 20°C / min and the internal cooling rate is 5°C / min to 10°C / min.

4. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The low temperature impact toughness test of the steel is a Charpy impact test carried out at -40°C.

5. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The temperature of the normalizing treatment is 870° C., the temperature of the tempering treatment is 420° C., and the holding time is 1 hour.

6. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The surface polishing treatment includes adopting mechanical polishing, sandblasting or grinding process to remove the surface defects of steel.

7. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The low-temperature impact toughness of the steel is improved by at least 30%, and in an impact test at -40°C, the Charpy impact value reaches more than 35J.

8. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The heat treatment step further includes performing a surface oxidation treatment after tempering to enhance the corrosion resistance of the steel.

9. The production process of LCC steel with excellent low temperature impact toughness according to claim 1, characterized in that: The steel is suitable for use in low temperature environments, and is particularly suitable for use as structural materials for low temperature containers, refrigeration equipment, pipelines, ships, and the like.

10. A process for producing LCC steel with excellent low temperature impact toughness according to any one of claims 1 to 9, characterized in that: The process significantly improves the low-temperature impact toughness of LCC steel by optimizing the chemical composition, smelting process, casting process, heat treatment process and post-surface treatment, and ensures its stable mechanical properties, making it suitable for high-demand low-temperature applications.