Production method for improving surface corrosion of HRB400E deformed steel bar

Abstract

The invention discloses a production method for improving surface corrosion of HRB400E deformed steel bar. The production method comprises the following steps: (1) heating a steel billet, wherein the heating time of the steel billet in a furnace is not less than 60 minutes, the temperature of a preheating section is less than or equal to 900 DEG C, the temperature of a heating section is 1130-1190 DEG C, the temperature of a soaking section is 1110-1170 DEG C, and the soaking time is 30-40 minutes; (2) rolling: controlling the initial rolling temperature of the discharged steel billet to be 950-1020 DEG C, controlling the finish rolling temperature to be 840-880 DEG C, controlling the first reducing temperature to be 830-850 DEG C, controlling the second reducing temperature to be 830-850 DEG C, and controlling the spinning temperature to be 840-860 DEG C; (3) an air cooling roller way controlled cooling process: four groups of delta-shaped fans are adopted, and the opening degrees of each group of fans are respectively set to be 70%, 100% and 100%; the speed of the first-section roller way is set to be 0.70 m / s, the speed of all the roller ways behind is set to be 0.75 m / s, and the cooling rate is controlled to be 3-5 DEG C / s; according to the deformed steel bar produced through the method, the diameter specification is phi 10-12 mm, the yield strength is 430-470 MPa, the tensile strength is 610-630 MPa, the average oxide scale thickness is 10-13 microns, and the deformed steel bar has good surface corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of steel material manufacturing, in particular to a production method for improving surface corrosion of HRB400E threaded steel. Background Art

[0002] Rebar is a common construction steel material, widely used in various construction projects. Its main features are high strength, good durability and convenient construction, so it is widely used in bridges, roads, buildings and other fields. Since the surface oxide scale of rebar is easily damaged during transportation and storage, the surface rust of rebar affects the market reputation and market share. Such rebar will also cause great safety hazards to the building itself.

[0003] Surface corrosion of rebar will cause several major hazards: 1. Reduced strength: Rust will weaken the cross-sectional area of ​​the rebar, resulting in a decrease in its bearing capacity and affecting structural safety; 2. Reduced durability: Rust will accelerate the aging of steel, shorten its service life, and increase maintenance and replacement costs; 3. Weakened adhesion: The adhesion between rebar and concrete is weakened due to corrosion, affecting the integrity and seismic performance of the structure; 4. Damaged appearance: Rust affects the appearance, especially in exposed areas, reducing the aesthetics of the building; 5. Safety hazards: Severe corrosion may cause structural failure, especially in key areas, increasing safety risks; 6. Increased maintenance costs: Rust requires frequent maintenance or replacement, increasing the economic burden; 7. Environmental impact: The rust produced by corrosion may pollute the environment, especially in sensitive areas. Summary of the invention

[0004] The purpose of the present invention is to provide a production method for improving the surface corrosion of HRB400E threaded steel in view of the problem that the existing HRB400E threaded steel is relatively easy to produce surface corrosion, which leads to a series of potential hazards.

[0005] A production method for improving the surface corrosion of HRB400E threaded steel of the present invention comprises the following steps: (1) Billet heating: The billet heating time in the furnace is not less than 60 minutes, the preheating section temperature is ≤900°C, the heating section temperature is 1130°C-1190°C, the soaking section temperature is 1110°C-1170°C, and the soaking time is 30-40 minutes; (2) Rolling: The starting rolling temperature of the steel billet is controlled at 950-1020°C, the finishing rolling temperature is controlled at 840-880°C, the first reducing temperature is controlled at 830-850°C, the second reducing temperature is controlled at 830-850°C, and the wire drawing temperature is controlled at 840-860°C; (3) Air-cooled roller controlled cooling process: four groups of zigzag fans, each group of fans opening degree is set to 70%, 100%, 100% respectively; the first section roller speed is set to 0.70m / s, and the subsequent roller speeds are set to 0.75m / s, and the cooling rate is controlled to 3-5℃ / s.

[0006] The invention discloses a production method for improving the surface corrosion of HRB400E threaded steel. The steel billet comprises the following chemical components by mass fraction: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, and the rest is Fe and unavoidable impurities, and also satisfies the following condition: Ceq: 0.37-0.50%.

[0007] The threaded steel produced by the method of the invention has a diameter specification of Φ10-12 mm, a yield strength of 430-470 MPa, a tensile strength of 610-630 MPa, and an average iron oxide scale thickness of 10-13 μm.

[0008] The reasons for setting the process parameters of the production method of threaded steel of the present invention are described in detail below.

[0009] The present invention conducts an in-depth analysis of the causes of rust on the surface of threaded steel bars, and finds that a moderate thickness of iron oxide scale on the surface of threaded steel bars can effectively prevent rust. When the thickness of the iron oxide scale on the surface of threaded steel bars is 10-13 μm, the occurrence of rust on the surface of threaded steel bars can be well improved. When the thickness of the iron oxide scale on the surface of threaded steel bars is less than 10 μm, the surface of the steel bar is prone to rust, and when the thickness of the iron oxide scale on the surface of threaded steel bars is greater than 13 μm, the iron oxide scale is easy to fall off and slightly reduces the strength of the steel bar.

[0010] Therefore, the production method of the present invention is based on the above theoretical research. The inventors found that the thickness of the oxide scale on the surface of rebar is greatly affected by the spinning temperature, cooling rate and alloy composition. At the same cooling rate, the higher the spinning temperature, the thicker the surface oxide scale; when the spinning temperature is lower than 865°C, the faster the cooling rate, the thicker the surface oxide scale; when the spinning temperature is higher than 865°C, the slower the cooling rate, the thicker the surface oxide scale; the higher the silicon alloy component, the more it promotes the formation of oxide scale, and the higher the manganese alloy component, the slower the formation of oxide scale; Combining the above theoretical research results and actual production conditions, the specific rolling process parameters and cooling process parameters of the present invention are formulated as follows: (1) Billet heating: The billet is heated in the furnace for not less than 60 minutes, the preheating section temperature is ≤900°C, the heating section temperature is 1130°C-1190°C, and the soaking section temperature is 11 10℃-1170℃, soaking time 30-40min; (2) Rolling: the starting rolling temperature of the steel billet out of the furnace is controlled at 950℃-1020℃, the finishing rolling temperature is controlled at 840-880℃, the first reducing temperature is controlled at 830-850℃, the second reducing temperature is controlled at 830-850℃, and the wire drawing temperature is controlled at 840-860℃; (3) Air-cooled roller cooling process: four groups of triangular fans, the opening degree of each group of fans is set to 70%, 100%, and 100% respectively; the speed of the first roller is set to 0.70m / s, and the speed of all subsequent rollers is set to 0.75m / s, and the cooling rate is controlled to 3-5℃ / s. The chemical composition design content of the present invention is specifically as follows: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, and the rest is Fe and unavoidable impurities, and also meets the following conditions: Ceq: 0.37-0.50%.

[0011] The present invention utilizes the promoting effect of silicon alloy on the production of surface iron oxide scale during the rolling process of threaded steel bars, and increases the silicon alloy content to 0.55-0.65%. On the one hand, the yield strength of the threaded steel bars can be improved, and on the other hand, the thickness of the iron oxide scale on the surface of the threaded steel bars can be increased. At the same time, the spinning temperature is increased to 840-860°C, and the air cooling rate after rolling is accelerated to promote the generation of iron oxide scale on the surface of the threaded steel bars, so as to achieve an ideal thickness of 10-13 μm of iron oxide scale on the surface of the threaded steel bars, so that the iron oxide scale on the surface of the threaded steel bars is not easy to fall off during the production process, and the occurrence of surface corrosion of HRB400E threaded steel bars is improved to the greatest extent. DETAILED DESCRIPTION

[0012] In order to better explain the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with specific embodiments. The following embodiments are merely exemplary of the technical solution of the present invention and do not limit the present invention in any form. The serial numbers of the following embodiments are only for description and do not represent the advantages and disadvantages of the embodiments.

[0013] Table 1 below is a list of chemical composition values ​​(wt, %) of the threaded steel billets of various embodiments of the present invention; Table 2 below is a list of specific rolling process parameter values ​​of threaded steel in various embodiments of the present invention; Table 3 below is a list of the main performance test results and surface oxide scale thickness test results of the threaded steel in various embodiments of the present invention.

[0014] A production method for improving surface corrosion of HRB400E threaded steel according to various embodiments of the present invention comprises the following steps: (1) Billet heating: The billet heating time in the furnace is not less than 60 minutes, the preheating section temperature is ≤900°C, the heating section temperature is 1130°C-1190°C, the soaking section temperature is 1110°C-1170°C, and the soaking time is 30-40 minutes; (2) Rolling: The starting rolling temperature of the steel billet is controlled at 950-1020°C, the finishing rolling temperature is controlled at 840-880°C, the first reducing temperature is controlled at 830-850°C, the second reducing temperature is controlled at 830-850°C, and the wire drawing temperature is controlled at 840-860°C; (3) Air-cooled roller controlled cooling process: four groups of zigzag fans, each group of fans opening degree is set to 70%, 100%, 100% respectively; the first section roller speed is set to 0.70m / s, and the subsequent roller speeds are set to 0.75m / s, and the cooling rate is controlled to 3-5℃ / s.

[0015] Table 1 List of chemical composition values ​​of threaded steel billets in various embodiments of the present invention (wt, %)

[0016] Table 2 List of specific rolling process parameter values ​​of threaded steel in various embodiments of the present invention

[0017] Table 3 List of main performance test results and surface oxide scale thickness test results of threaded steel in various embodiments of the present invention

[0018] It can be seen from Table 3 above that the yield strength and tensile strength of the HRB400E rebar produced by the method of the present invention meet the strength requirements of HRB400E rebar, the thickness of the oxide scale is 10-13 μm, and it has good surface corrosion resistance.

[0019] The above embodiments are only specific examples for explaining the present invention and do not limit the present invention in any form. Any non-substantial changes made by anyone based on the above contents and forms without departing from the protection scope of the claims of the present invention shall be deemed to fall within the protection scope of the claims of the present invention. The present invention is not limited to the above specific implementation examples.

Claims

1. A production method for improving the surface corrosion of HRB400E threaded steel, characterized in that The steps include: (1) Billet heating: The billet heating time in the furnace is not less than 60 minutes, the preheating section temperature is ≤900°C, the heating section temperature is 1130°C-1190°C, the soaking section temperature is 1110°C-1170°C, and the soaking time is 30-40 minutes; (2) Rolling: The starting rolling temperature of the steel billet is controlled at 950-1020°C, the finishing rolling temperature is controlled at 840-880°C, the first reducing temperature is controlled at 830-850°C, the second reducing temperature is controlled at 830-850°C, and the wire drawing temperature is controlled at 840-860°C; (3) Air-cooled roller controlled cooling process: four groups of zigzag fans, each group of fans opening degree is set to 70%, 100%, 100% respectively; the first section roller speed is set to 0.70m / s, and the subsequent roller speeds are set to 0.75m / s, and the cooling rate is controlled to 3-5℃ / s.

2. The production method for improving the surface corrosion of HRB400E threaded steel according to claim 1, characterized in that: The steel billet contains the following chemical components by mass fraction: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, and the rest is Fe and unavoidable impurities, and also satisfies the following conditions: Ceq: 0.37-0.50%.

3. The production method for improving the surface corrosion of HRB400E threaded steel according to claim 1, characterized in that: The diameter of the produced rebar is Φ10-12mm, the yield strength is 430-470MPa, the tensile strength is 610-630MPa, and the average oxide scale thickness is 10-13μm.

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