A production method of a rare earth cerium microalloyed low-cost 400MPa corrosion-resistant steel bar

Abstract

The application discloses a production method of a rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant steel bar, and mainly comprises the following steps: converter-LF refining-continuous casting-rolling. The chemical components of the steel bar are as follows (in wt%): C: 0.20-0.25%, Si: 0.50-0.60%, Mn: 1.35-1.45%, Cr: 0.10-0.15%, the adding amount of rare earth Ce is 30ppm, and the balance is Fe and inevitable impurity elements. The application aims to solve the corrosion problem of the steel bar, realize the upgrading of the steel bar for concrete, and improve the strength and service life of the steel bar.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of smelting and rolling process technology, and particularly relates to a production method of a rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant steel bar. BACKGROUND

[0002] Atmospheric corrosion resistant steel is generally a kind of low-alloy steel with good atmospheric corrosion resistance prepared by adding a certain amount of Cu, P or Ni, Mo, Nb, Ti, Cr and other alloying elements. The mechanism of atmospheric corrosion resistant steel is mainly that in the presence of water film, oxygen in the air undergoes an electrochemical reaction process through the rust layer, and the rust layer is composed of a loose outer rust layer and a dense inner rust layer, and the alloying elements in the steel mainly act through the influence of the inner rust layer. Generally, in the corrosion products of atmospheric corrosion resistant steel, a dense inner rust layer of Cu, P and Cr can be observed.

[0003] The corrosion resistance of steel bars has become a major research topic in industrialized countries, and the use range of various corrosion-resistant steel bars with high service life and weather-resistant steel bars is increasingly expanding, but for ordinary corrosion-resistant steel bars, not only a certain corrosion resistance is required, but also the production cost is economically sufficient. In order to solve this problem, the present application provides a low-cost economic corrosion-resistant steel bar which does not use expensive alloys such as V and Nb. SUMMARY

[0004] The purpose of the present application is to provide a production method of a rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant steel bar, to solve the corrosion problem of steel bars, to realize the upgrading of steel bars for concrete, and to improve the strength and service life of steel bars.

[0005] To solve the above technical problems, the present application adopts the following technical scheme:

[0006] The production method of a rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant steel bar of the present application mainly includes the following production steps:

[0007] The converter adopts combined blowing converter smelting, single slag operation, and the final slag basicity is controlled at 2.0. The converter adopts low carbon drawing process, and the target C at the end of the converter is not greater than 0.06%, and the tapping temperature is controlled to be not less than 1630℃. Manganese iron and silicon manganese are used for refining, and aluminum deoxidization is used for final deoxidization. Non-metallic inclusions in the steel have a greater impact on the corrosion resistance of the steel, and a modifying agent needs to be added to the molten steel during LF refining. In the production of this atmospheric corrosion resistant steel bar, the addition of rare earth cerium alloy makes the non-metallic inclusions spheroidized, eliminates or reduces their adverse effects on the properties of the steel, thereby purifying the steel, reducing the total amount of inclusions, and reducing the corrosion between the contact surfaces of the inclusions and the steel matrix;

[0008] The drawing speed is controlled at 2.1-2.3 m / min, and weak cooling is adopted for the secondary cooling of the continuous casting due to the addition of the alloy, so as to prevent the surface cracks and internal defects of the casting blank and ensure the constant drawing speed of the continuous casting blank as much as possible;

[0009] The heating temperature of the casting blank is controlled at 1100-1200 DEG C, the discharging temperature of the steel blank is 1050-1150 DEG C, the opening rolling temperature is 950-1050 DEG C, and the final rolling temperature is 850-900 DEG C.

[0010] The chemical composition of the reinforcing steel bar is as follows: C: 0.20-0.25%, Si: 0.50-0.60%, Mn: 1.35-1.45%, Cr: 0.10-0.15%, the addition amount of rare earth Ce is 30 ppm, and the balance is Fe and inevitable impurity elements.

[0011] Further, the chemical composition of the reinforcing steel bar is as follows: C: 0.24%, Si: 0.52%, Mn: 1.38%, Cr: 0.12%, rare earth Ce 15 ppm, P 0.025%, S 0.034%, and the balance is Fe and inevitable impurity elements.

[0012] Further, the drawing speed is controlled at 2.2 m / min.

[0013] Further, the cross section of the casting blank is 150 mm*150 mm, and the length of the casting blank is 11.5 m.

[0014] Further, the rolling temperature is 1050±20 DEG C.

[0015] Compared with the prior art, the beneficial technical effects of the present application are as follows:

[0016] The rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant reinforcing steel bar prepared by the present application has good corrosion resistance and good mechanical properties. DETAILED DESCRIPTION

[0017] The present application will be further described below in combination with examples.

[0018] The chemical composition of the rare earth cerium micro-alloyed low-cost 400MPa corrosion-resistant reinforcing steel bar in the present example is shown in Table 1. The main preparation process of the reinforcing steel bar is as follows: converter-LF refining-continuous casting-rolling.

[0019] Converter: top and bottom combined blowing is adopted for decarburization and dephosphorization, and the steel liquid is smelted at 1650 DEG C until the carbon content is lower than 0.05% and the phosphorus content is lower than 0.01% before tapping, the steel liquid is stirred by the protective gas at a pressure of 0.5 MPa during the tapping process, silicon iron and silicon manganese alloy are added for deoxidization when the tapping process is to 1 / 4, carbon powder and slagging materials are added, a large amount of slag is prevented from being discharged during the tapping, and the pressure of the protective gas is gradually reduced with the tapping amount.

[0020] Refining: LF furnace outer refining is adopted, and the oxygen content in the molten steel is deoxidized to 0.002%, manganese iron and silicon-manganese alloy are added, calcium iron alloy wire and rare earth cerium alloy are fed after the refining is completed, and the soft blowing time is ensured to be not less than 10 min.

[0021] Continuous casting: the constant speed is ensured as much as possible to pull the steel, the casting speed is controlled to be 2.2 m / min, the cross section of the casting blank is 150 mm x 150 mm, and the length of the casting blank is 11.5 m.

[0022] Rolling: the specific rolling process is shown in Table 2, the continuous casting blank is heated to 1200 DEG C, the temperature is measured to be about 1200 DEG C when discharging, high-pressure water descaling is performed after rolling, the rolling temperature is 1050±20 DEG C, after rough rolling and medium rolling, the final rolling temperature is controlled to be 850-900 DEG C, then the cold bed is entered, and the finishing, bundling process is entered.

[0023] Table 1 Chemical composition of the low-cost 400 MPa corrosion-resistant reinforcing bar of rare earth cerium micro-alloying

[0024]

[0025]

[0026] Table 2 Rolling process of the low-cost 400 MPa corrosion-resistant reinforcing bar of rare earth cerium micro-alloying

[0027] Process variant Delivery temperature / °C Breakdown temperature / °C Entry finish rolling temperature / °C Finishing temperature / °C 1200±20 1050±20 1050±20 850～900

[0028] Table 3 Mechanical property results of the low-cost 400 MPa corrosion-resistant reinforcing bar of rare earth cerium micro-alloying

[0029] No. [R p0.2 / MPa]]> [R m / MPa]]> A％ Example 1 442 643 24.0 Example 2 445 646 28.0 Example 3 450 640 26.0 Example 4 448 647 25.0

[0030] It can be seen that the pre-degree performance of each embodiment of the application is excellent, the elongation is 24-28%, and the yield strength ratio is less than 0.72.

[0031] The above-described embodiments are only used to describe the preferred modes of the application, and do not limit the scope of the application, and various modifications and improvements to the technical solutions of the application made by those skilled in the art without departing from the design spirit of the application shall fall within the protection scope of the claims of the application.

Claims

1. A method for producing low-cost, 400MPa corrosion-resistant steel bars with rare earth cerium microalloying, characterized in that: Its production steps mainly include: The converter adopts a combined blowing converter smelting process, using single-slag operation, with the final slag basicity controlled at 2.

0. The converter uses a low-carbon extraction process, with the final target C not exceeding 0.06%, and the tapping temperature controlled at not less than 1630℃. Refining uses ferromanganese and ferrosilicon, and final deoxidation uses aluminized deoxidation. Non-metallic inclusions in steel have a significant impact on the corrosion resistance of steel. LF refining requires the addition of modifiers to the molten steel. In the production of this atmospheric corrosion resistant steel bar, the addition of rare earth cerium alloy modifies and spheroidizes non-metallic inclusions, eliminating or reducing their adverse effects on steel properties, thereby purifying the steel, reducing the total amount of inclusions, and reducing corrosion between inclusions and the steel matrix. The casting speed is controlled at 2.1 to 2.3 m / min. Due to the addition of the alloy, the secondary cooling water supply for continuous casting adopts weak cooling to prevent surface cracks and internal defects in the billet, while ensuring a constant casting speed to obtain the continuous casting billet as much as possible. The billet heating temperature is controlled at 1100~1200℃, the billet exit temperature is 1050~1150℃, the initial rolling temperature is 950~1050℃, and the final rolling temperature is 850~900℃. The chemical composition of the steel reinforcement by mass percentage is as follows: C: 0.20-0.25%, Si: 0.50-0.60%, Mn: 1.35-1.45%, Cr: 0.10-0.15%, rare earth Ce added at 30 ppm, with the balance being Fe and unavoidable impurity elements.

2. The method for producing low-cost 400MPa corrosion-resistant steel bars with rare earth cerium microalloying according to claim 1, characterized in that: The chemical composition of the steel reinforcement by weight percentage is as follows: C: 0.24%, Si: 0.52%, Mn: 1.38%, Cr: 0.12%, rare earth Ce 15ppm, P 0.025%, S 0.034%, with the balance being Fe and unavoidable impurity elements.

3. The method for producing low-cost 400MPa corrosion-resistant steel bars with rare earth cerium microalloying according to claim 2, characterized in that: The pulling speed is controlled at 2.2 m / min.

4. The method for producing low-cost 400MPa corrosion-resistant steel bars with rare earth cerium microalloying according to claim 2, characterized in that: The billet has a cross-section of 150mm × 150mm and a length of 11.5m.

5. The method for producing low-cost 400MPa corrosion-resistant steel bars with rare earth cerium microalloying according to claim 2, characterized in that: Rolling temperature 1050±20℃.

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