Production method for improving corrosion resistance of cold forging steel

Abstract

The invention discloses a production method for improving the corrosion resistance of cold forging steel. The production process specifically comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, VD vacuum degassing and square billet continuous casting production. The cold forging steel comprises the following chemical components in percentage by weight: 0.41 to 0.45 percent of C, 0.75 to 0.80 percent of Si, 0.70 to 0.75 percent of Mn, less than or equal to 0.018 percent of P, less than or equal to 0.008 percent of S, 0.08 to 0.10 percent of V, less than or equal to 0.006 percent of Nb, 0.90 to 1.00 percent of Cr, 0.01 to 1.00 percent of Ni, 0 to 0.40 percent of Cu, 0.21 to 0.25 percent of Mo and the balance of iron and impurities. The cold forging steel produced through the method meets the requirements that the tensile strength is larger than or equal to 1000 MPa, the percentage elongation after fracture is larger than or equal to 13%, the percentage reduction of area is larger than or equal to 30%, and the relative corrosion rate of contrast sample / corrosion-resistant cold forging steel is larger than or equal to 150%.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a production method for improving the corrosion resistance of cold heading steel. Background Art

[0002] Cold heading steel is a type of high-quality structural steel. As the name suggests, at room temperature, the material can be extruded into shape with the help of the constraints of the mold, and no or very little material is removed during the forming process. The yield rate is high and it has good dimensional accuracy and surface quality.

[0003] Cold heading steel is generally low-carbon high-quality carbon structural steel and high-quality alloy structural steel, which is used for cold heading to manufacture various mechanical standard parts and fasteners. Cold heading steel is widely used in fasteners, automobiles, engineering construction, machinery, electronics and other industries due to its excellent machining performance.

[0004] Improving the corrosion resistance of cold heading steel is very important because it can bring many benefits. First of all, cold heading steel is often used to manufacture fasteners such as bolts, nuts, screws, etc. These parts usually need to work in harsh environments, such as outdoors, marine environments or chemical plants. If these parts lack corrosion resistance, they will quickly corrode, resulting in a shortened service life or even failure, which will affect the safety and reliability of the equipment. Secondly, improving the corrosion resistance of cold heading steel can reduce maintenance costs. If parts are susceptible to corrosion, they need to be maintained and replaced more frequently, which will increase maintenance costs and downtime. Cold heading steel with good corrosion resistance can reduce these maintenance frequencies, reduce maintenance costs, and improve the reliability and stability of equipment. In addition, corrosion resistance is also a regulatory requirement for cold heading steel in specific industries. For example, in the food processing industry, medical device manufacturing and other fields, there are strict requirements for the corrosion resistance of materials to ensure the safety and hygiene of products. Therefore, improving the corrosion resistance of cold heading steel can make it meet the regulatory standards of relevant industries, thereby expanding the scope of application and improving market competitiveness. Finally, with the development of science and technology, the requirements for material performance are constantly increasing, and corrosion resistance has become one of the important directions for the research and development of cold heading steel materials. By improving material formulations, surface treatment processes and other means, the corrosion resistance of cold heading steel can be improved, making it adaptable to a wider range of application scenarios and meeting the needs of different industries. In summary, improving the corrosion resistance of cold heading steel is of great significance for improving product reliability, reducing maintenance costs, complying with regulatory requirements and adapting to market demand. Therefore, in the research and development and production of cold heading steel materials, improving corrosion resistance is a direction worthy of attention. Summary of the invention

[0005] The purpose of the present invention is to provide a production method for improving the corrosion resistance of cold heading steel. The produced cold heading steel meets the following requirements: tensile strength ≥1000MPa, elongation after fracture ≥13%, cross-sectional shrinkage ≥30%, and relative corrosion rate: comparison sample / corrosion-resistant cold heading steel ≥150%.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention discloses a production method for improving the corrosion resistance of cold heading steel, and the production process specifically comprises: molten iron pretreatment - converter smelting - LF furnace refining - VD vacuum degassing - billet continuous casting production; wherein:

[0008] Before smelting, the molten iron is first desulfurized to reduce the sulfur content in the molten steel;

[0009] In the converter smelting process, the slag washing process is adopted, lime and refining slag are added, and the good dynamic conditions of converter steel discharge are utilized to prepare the pre-slag for the refining furnace smelting;

[0010] During the LF refining process, lime, refining slag and fluorite are added, and argon is blown from the bottom for stirring throughout the process;

[0011] The molten steel after ladle refining is vacuum degassed in a VD furnace to further reduce the harmful gas content in the steel and improve the cleanliness of the steel;

[0012] The casting machine is used to produce continuous casting billets. The continuous casting process adopts full-process protection casting to prevent secondary oxidation of molten steel. The H content in the billet is less than 2.5ppm, and the composition and gas content of the finished continuous casting billet meet the design requirements.

[0013] During the steel rolling process, the technical parameters controlled in the high-speed wire rolling process are:

[0014] Rolling temperature: 1020±20℃;

[0015] Final rolling temperature 880±20℃;

[0016] The cooling beds are closely packed and the spacing is less than 10mm;

[0017] The heating temperature of the steel billet should be uniform, and overheating and overburning of the steel billet are strictly prohibited;

[0018] The surface of the steel billet is descaled by high-pressure water, and the straightening temperature does not exceed 60°C. After straightening, the cold heading steel is straight without wave bends, hard bends and obvious distortions;

[0019] The chemical composition percentages of the cold heading steel are: C: 0.41-0.45%, Si: 0.75-0.80%, Mn: 0.70-0.75%, P: ≤0.018%, S: ≤0.008%, V: 0.08-0.10%, Nb: ≤0.006%, Cr: 0.90-1.00%, Ni: 0.01-1.00%, Cu: 0-0.40%, Mo: 0.21-0.25%, and the rest are iron and inevitable trace chemical elements.

[0020] Furthermore, the chemical composition percentages of the cold heading steel are: C: 0.41%, Si: 0.76%, Mn: 0.70%, P: 0.012%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.90%, Ni: 0.01%, Cu: 0%, Mo: 0.21%, and the rest are iron and inevitable trace chemical elements.

[0021] Furthermore, the chemical composition percentages of the cold heading steel are: C: 0.42%, Si: 0.78%, Mn: 0.70%, P: 0.012%, S: 0.006%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.52%, Cu: 0.22%, Mo: 0.21%, and the rest are iron and inevitable trace chemical elements.

[0022] Furthermore, the chemical composition percentages of the cold heading steel are: C: 0.42%, Si: 0.78%, Mn: 0.70%, P: 0.009%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.92%, Cu: 0.40%, Mo: 0.22%, and the rest are iron and inevitable trace chemical elements.

[0023] Furthermore, the properties of the produced cold heading steel meet the following requirements: tensile strength ≥ 1000 MPa, elongation after fracture ≥ 13%, cross-sectional shrinkage ≥ 30%, and relative corrosion rate: comparison sample / corrosion-resistant cold heading steel ≥ 150%.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are:

[0025] It can be seen from the experimental results that the corrosion-resistant cold heading steel produced by the present invention has a lower weight loss rate and a better corrosion resistance. DETAILED DESCRIPTION

[0026] Below in conjunction with embodiment, the present invention is described in further detail:

[0027] This embodiment provides a production method for improving the corrosion resistance of cold heading steel, wherein the tensile strength of the cold heading steel is ≥1000MPa, the elongation after fracture is ≥13%, the cross-sectional shrinkage is ≥30%, and the relative corrosion rate: the comparison sample / corrosion-resistant cold heading steel is ≥150%. The method sequentially comprises the steps of molten iron pretreatment, converter smelting, LF furnace refining, VD vacuum degassing, continuous casting production, and high-speed wire rolling.

[0028] The specific ingredients of each embodiment are as follows:

[0029] Embodiment 1: The chemical composition percentage of the cold heading steel is: C: 0.41%, Si: 0.76%, Mn: 0.70%, P: 0.012%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.90%, Ni: 0.01%, Cu: 0%, Mo: 0.21%, and the rest is iron and inevitable trace chemical elements.

[0030] Embodiment 2: The chemical composition percentage of the cold heading steel is: C: 0.42%, Si: 0.78%, Mn: 0.70%, P: 0.012%, S: 0.006%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.52%, Cu: 0.22%, Mo: 0.21%, and the rest is iron and inevitable trace chemical elements.

[0031] Embodiment 3: The chemical composition percentage of the cold heading steel is: C: 0.42%, Si: 0.78%, Mn: 0.70%, P: 0.009%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.92%, Cu: 0.40%, Mo: 0.22%, and the rest is iron and inevitable trace chemical elements.

[0032] The process parameters of cold upsetting steel rolled in each embodiment are shown in Table 2:

[0033] Table 2: Process parameters of cold-forging steel rolled in various embodiments

[0034]

[0035] The process parameters of cold upsetting steel rolled in each embodiment are shown in Table 3:

[0036] Table 3: Mechanical properties of cold-forged steel after rolling in various examples

[0037]

[0038] Corrosion resistance:

[0039] This experiment is based on my country's atmospheric environment and the national standard GB / T18175-2000 rotating hanging plate method to conduct a periodic immersion accelerated corrosion experiment. The experiment uses a 3.5% NaCl solution. Experimental time: 24, 48, 72 hours; experimental temperature: 40±1℃; rotation speed: 120 rpm. The weightless sample is suspended in the periodic immersion corrosion box with plastic insulating material. The sample suspension height is kept consistent and the sample position is recorded. The experiment is three cycles totaling 72 hours. The weightless samples are taken out at 24h, 48h, and 72h for corresponding corrosion analysis.

[0040] The corrosion rates of cold-headed steel rolled in various embodiments are summarized in Table 4:

[0041] Table 4: Corrosion rate of cold-forged steel after rolling in various examples (g / m 2 / h)Summary

[0042]

[0043] Through random sampling of the above production results, it can be analyzed from Table 4 that the cold heading steel has a lower corrosion resistance weight loss rate and better corrosion resistance.

[0044] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method for improving the corrosion resistance of cold heading steel, characterized in that: The production process specifically includes: molten iron pretreatment - converter smelting - LF furnace refining - VD vacuum degassing - billet continuous casting production; among which: Before smelting, the molten iron is first desulfurized to reduce the sulfur content in the molten steel; In the converter smelting process, the slag washing process is adopted, lime and refining slag are added, and the good dynamic conditions of the converter steel are used to make the pre-slag for the refining furnace smelting; During the LF refining process, lime, refining slag and fluorite are added, and argon is blown from the bottom for stirring throughout the process; The molten steel after ladle refining is vacuum degassed in a VD furnace to further reduce the harmful gas content in the steel and improve the cleanliness of the steel; The casting machine is used to produce continuous casting billets. The continuous casting process adopts full-process protection casting to prevent secondary oxidation of molten steel. The H content in the billet is less than 2.5ppm, and the composition and gas content of the finished continuous casting billet meet the design requirements. During the steel rolling process, the technical parameters controlled in the high-speed wire rolling process are: Rolling temperature 1020±20℃; Final rolling temperature 880±20℃; The cooling beds are closely packed and the spacing is less than 10mm; The heating temperature of the steel billet should be uniform, and overheating and overburning of the steel billet are strictly prohibited; The surface of the steel billet is descaled by high-pressure water, and the straightening temperature does not exceed 60°C. After straightening, the cold heading steel is straight without wave bends, hard bends and obvious distortions; The chemical composition percentages of the cold heading steel are: C: 0.41-0.45%, Si: 0.75-0.80%, Mn: 0.70-0.75%, P: ≤0.018%, S: ≤0.008%, V: 0.08-0.10%, Nb: ≤0.006%, Cr: 0.90-1.00%, Ni: 0.01-1.00%, Cu: 0-0.40%, Mo: 0.21-0.25%, and the rest are iron and inevitable trace chemical elements.

2. The production method for improving the corrosion resistance of cold heading steel according to claim 1, characterized in that: The chemical composition percentages of the cold heading steel are: C: 0.41%, Si: 0.76%, Mn: 0.70%, P: 0.012%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.90%, Ni: 0.01%, Cu: 0%, Mo: 0.21%, and the rest are iron and inevitable trace chemical elements.

3. The production method for improving the corrosion resistance of cold heading steel according to claim 1, characterized in that: The chemical composition percentages of the cold heading steel are: C: 0.42%, Si: 0.78%, Mn: 0.72%, P: 0.012%, S: 0.006%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.52%, Cu: 0.22%, Mo: 0.21%, and the rest are iron and inevitable trace chemical elements.

4. The production method for improving the corrosion resistance of cold heading steel according to claim 1, characterized in that: The chemical composition percentages of the cold heading steel are: C: 0.42%, Si: 0.78%, Mn: 0.73%, P: 0.009%, S: 0.005%, V: 0.08%, Nb: 0.005%, Cr: 0.92%, Ni: 0.92%, Cu: 0.40%, Mo: 0.22%, and the rest are iron and inevitable trace chemical elements.

5. The production method for improving the corrosion resistance of cold heading steel according to claim 1, characterized in that: The properties of the produced cold heading steel meet the following requirements: tensile strength ≥ 1000MPa, elongation after fracture ≥ 13%, cross-sectional shrinkage ≥ 30%, relative corrosion rate: comparison sample / corrosion-resistant cold heading steel ≥ 150%.

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