Production method for improving surface rust of HRB400E threaded steel

Abstract

This invention discloses a production method for improving surface corrosion of HRB400E rebar, comprising the following steps: (1) billet heating: the billet is heated in the furnace for no less than 60 minutes, the preheating zone temperature is ≤900℃, the heating zone temperature is 1130℃-1190℃, the soaking zone temperature is 1110℃-1170℃, and the soaking time is 30-40 minutes; (2) rolling: the initial rolling temperature of the billet exiting the furnace is controlled at 950℃-1020℃, the finishing rolling temperature is controlled at 840-880℃, the first reduction rolling temperature is controlled at 830-850℃, and the second reduction rolling temperature is controlled at 830-850℃. The wire drawing temperature is controlled at 840-860℃; (3) Air-cooled roller conveyor cooling process: four sets of triangular fans, each set of fans with an opening degree of 70%, 100%, and 100% respectively; the speed of the first section of roller conveyor is set to 0.70m / s, and the speed of all subsequent roller conveyors is set to 0.75m / s, and the cooling rate is controlled at 3-5℃ / s; the diameter of the rebar produced by the method of this invention is Φ10-12mm, the yield strength is 430-470MPa, the tensile strength is 610-630MPa, the average iron oxide scale thickness is 10-13μm, and it has good resistance to surface corrosion.

Description

Technical Field

[0001] This invention relates to the field of steel material manufacturing technology, and in particular to a production method for improving surface corrosion of HRB400E rebar. Background Technology

[0002] Rebar is a common type of construction steel, widely used in various construction projects. Its main characteristics are high strength, good durability, and ease of construction, making it widely used in bridges, roads, and buildings. However, the iron oxide scale on the surface of rebar is easily damaged during transportation and storage, leading to surface corrosion that affects its market reputation and market share. Such rebar can also pose significant safety hazards to the building itself.

[0003] Several hazards arise from surface corrosion of rebar: 1. Reduced strength: Corrosion weakens the cross-sectional area of ​​the rebar, reducing its load-bearing capacity and affecting structural safety; 2. Decreased durability: Corrosion accelerates steel aging, shortens its service life, and increases maintenance and replacement costs; 3. Weakened adhesion: Corrosion weakens the bond between the rebar and concrete, affecting the overall integrity and seismic performance of the structure; 4. Appearance damage: Corrosion affects the appearance, especially in exposed areas, reducing the building's aesthetics; 5. Safety hazards: Severe corrosion may lead to structural failure, especially in critical areas, increasing safety risks; 6. Increased maintenance costs: Corrosion requires frequent maintenance or replacement, increasing the economic burden; 7. Environmental impact: Rust produced by corrosion may pollute the environment, especially in sensitive areas. Summary of the Invention

[0004] The purpose of this invention is to address the problem that existing HRB400E rebar is prone to surface corrosion, leading to a series of potential hazards, and to provide a production method that improves the surface corrosion of HRB400E rebar.

[0005] The present invention provides a production method for improving surface corrosion of HRB400E rebar, comprising the following steps:

[0006] (1) Steel billet heating: The steel billet is heated in the furnace for no less than 60 minutes, the preheating section temperature is ≤900℃, the heating section temperature is 1130℃-1190℃, the soaking section temperature is 1110℃-1170℃, and the soaking time is 30-40 minutes.

[0007] (2) Rolling: The initial rolling temperature of the billet is controlled at 950℃-1020℃, the temperature of the finishing mill is controlled at 840-880℃, the temperature of the first reduction mill is controlled at 830-850℃, the temperature of the second reduction mill is controlled at 830-850℃, and the wire drawing temperature is controlled at 840-860℃.

[0008] (3) Air-cooled roller conveyor controlled cooling process: four sets of three-pronged fans, with the opening degree of each fan set set to 70%, 100%, and 100% respectively; the speed of the first section of roller conveyor is set to 0.70m / s, and the speed of all subsequent roller conveyors is set to 0.75m / s, controlling the cooling rate to 3-5℃ / s.

[0009] The present invention discloses a production method for improving surface corrosion of HRB400E rebar, wherein the steel billet contains the following chemical composition by mass fraction: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, with the remainder being Fe and unavoidable impurities, and also satisfies the following condition: Ceq: 0.37-0.50%.

[0010] The rebar produced by the method of this invention has a diameter of Φ10-12mm, a yield strength of 430-470MPa, a tensile strength of 610-630MPa, and an average iron oxide scale thickness of 10-13μm.

[0011] The rationale for setting the process parameters in the rebar production method of the present invention is explained in detail below.

[0012] This invention, through in-depth analysis of the causes of rust on the surface of rebar, reveals that an appropriate thickness of iron oxide scale on the surface of rebar can effectively prevent rust. When the thickness of the iron oxide scale on the surface of the rebar is 10-13 μm, it can significantly reduce the occurrence of oxidative rust. When the thickness of the iron oxide scale on the surface of the rebar is <10 μm, the surface of the rebar is prone to rust, while when the thickness of the iron oxide scale is >13 μm, the iron oxide scale is prone to peeling off and has a slight reducing effect on the strength of the rebar.

[0013] Therefore, the production method of the present invention is based on the above theoretical research. The inventors found that the thickness of the iron oxide scale on the surface of the rebar is greatly affected by the coiling temperature, cooling rate and alloy composition. At the same cooling rate, the higher the coiling temperature, the thicker the iron oxide scale on the surface; when the coiling temperature is below 865℃, the faster the cooling rate, the thicker the iron oxide scale on the surface; when the coiling temperature is above 865℃, the slower the cooling rate, the thicker the iron oxide scale on the surface; the higher the silicon alloy composition, the more it promotes the formation of iron oxide scale, and the higher the manganese alloy composition, the slower the formation of iron oxide scale; based on 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) Steel billet heating: the steel billet is heated in the furnace for no less than 60 minutes, the preheating section temperature is ≤900℃, the heating section temperature is 1130℃-1190℃, and the soaking section temperature is 11 10℃-1170℃, heat soaking time 30-40min; (2) Rolling: the initial rolling temperature of the billet is controlled at 950℃-1020℃, the temperature of the finishing mill is controlled at 840-880℃, the temperature of the first reduction mill is controlled at 830-850℃, the temperature of the second reduction mill is controlled at 830-850℃, and the temperature of the wire drawing is controlled at 840-860℃; (3) Air-cooled roller cooling process: four sets of triangular fans, the opening degree of each set of fans is set to 70%, 100%, and 100% respectively; the speed of the first section of 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 at 3-5℃ / s. The chemical composition of this invention is designed to contain the following specific amounts: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, with the remainder being Fe and unavoidable impurities, while also satisfying the following condition: Ceq: 0.37-0.50%.

[0014] This invention utilizes the promoting effect of silicon alloy on the formation of surface iron oxide scale during the rolling process of rebar. By increasing the silicon alloy content to 0.55-0.65%, the yield strength of the rebar can be improved, and the thickness of the surface iron oxide scale can be increased. At the same time, the wire drawing temperature can be increased to 840-860℃, and the air cooling rate after rolling can be accelerated, which promotes the formation of surface iron oxide scale on the rebar and achieves an ideal surface iron oxide scale thickness of 10-13μm. This makes the surface iron oxide scale less likely to fall off during the production process, thus minimizing the occurrence of surface corrosion on HRB400E rebar. Detailed Implementation

[0015] To better explain the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments. The following embodiments are merely illustrative of the technical solution of the present invention and do not limit the present invention in any way. The sequence numbers of the following embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0016] Table 1 below is a list of chemical composition values ​​(wt, %) of rebar billets in various embodiments of the present invention.

[0017] Table 2 below lists the specific rolling process parameters for the rebar in various embodiments of the present invention;

[0018] Table 3 below lists the main performance test results and surface iron oxide scale thickness test results of the rebar in various embodiments of the present invention.

[0019] A production method for improving surface corrosion of HRB400E rebar according to various embodiments of the present invention includes the following steps:

[0020] (1) Steel billet heating: The steel billet is heated in the furnace for no less than 60 minutes, the preheating section temperature is ≤900℃, the heating section temperature is 1130℃-1190℃, the soaking section temperature is 1110℃-1170℃, and the soaking time is 30-40 minutes.

[0021] (2) Rolling: The initial rolling temperature of the billet is controlled at 950℃-1020℃, the temperature of the finishing mill is controlled at 840-880℃, the temperature of the first reduction mill is controlled at 830-850℃, the temperature of the second reduction mill is controlled at 830-850℃, and the wire drawing temperature is controlled at 840-860℃.

[0022] (3) Air-cooled roller conveyor controlled cooling process: four sets of three-pronged fans, with the opening degree of each fan set set to 70%, 100%, and 100% respectively; the speed of the first section of roller conveyor is set to 0.70m / s, and the speed of all subsequent roller conveyors is set to 0.75m / s, controlling the cooling rate to 3-5℃ / s.

[0023] Table 1. List of chemical composition values ​​(wt, %) of rebar billets in various embodiments of the present invention

[0024]

[0025] Table 2. List of specific rolling process parameters for rebar in various embodiments of the present invention.

[0026]

[0027] Table 3. List of main performance test results and surface iron oxide scale thickness test results for the rebar in various embodiments of the present invention.

[0028]

[0029] As can be seen from Table 3 above, the HRB400E rebar produced by the method of the present invention has yield strength and tensile strength that meet the strength requirements of HRB400E rebar, and the iron oxide scale thickness is 10-13μm, which has good resistance to surface corrosion.

[0030] The above embodiments are merely specific examples exemplified to explain the present invention and do not limit the present invention in any way. Any non-substantial changes made by any person based on the above content and form that do not depart from the scope of protection of the claims of the present invention should be considered to fall within the scope of protection of the claims of the present invention. The present invention is not limited to the specific embodiments described above.

Claims

1. A production method for improving surface corrosion of HRB400E rebar, characterized in that... Includes the following steps: (1) Steel billet heating: The steel billet is heated in the furnace for no less than 60 minutes, the preheating section temperature is ≤900℃, the heating section temperature is 1130℃-1190℃, the soaking section temperature is 1110℃-1170℃, and the soaking time is 30-40 minutes. (2) Rolling: The initial rolling temperature of the billet is controlled at 950℃-1020℃, the temperature of the finishing mill is controlled at 840-880℃, the temperature of the first reduction mill is controlled at 830-850℃, the temperature of the second reduction mill is controlled at 830-850℃, and the wire drawing temperature is controlled at 840-860℃. (3) Air-cooled roller conveyor controlled cooling process: four sets of ternary fans, each set of fans with an opening degree of 70%, 100%, and 100% respectively; the speed of the first section of roller conveyor is set to 0.70m / s, and the speed of all subsequent roller conveyors is set to 0.75m / s, and the cooling rate is controlled at 3-5℃ / s; The steel billet contains the following chemical composition by mass fraction: C: 0.26-0.28%, Si: 0.55-0.65%, Mn: 0.85-0.95%, P≤0.025%, S≤0.015%, with the remainder being Fe and unavoidable impurities. It also meets the following conditions: Ceq: 0.37-0.50%. The resulting rebar has a diameter of Φ10-12mm, a yield strength of 430-470MPa, a tensile strength of 610-630MPa, and an average iron oxide scale thickness of 10-13μm.

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