CN111088463B - Steel bar resistant to corrosion in low-temperature atmospheric environment and production method thereof - Google Patents

Abstract

A steel bar resisting corrosion in low temperature atmospheric environment and a production method thereof are disclosed, wherein the steel comprises the following chemical components in percentage by weight: 0.08 to 0.12 percent of C, 0.20 to 0.40 percent of Si, 1.40 to 1.60 percent of Mn, less than or equal to 0.011 percent of P, less than or equal to 0.005 percent of S, 0.04 to 0.06 percent of Cr, 0.05 to 0.08 percent of V, 0.05 to 0.06 percent of Cu, 0.05 to 0.08 percent of Sb, and the balance of Fe and inevitable impurities. The invention improves the atmospheric corrosion resistance of the low-temperature steel bar and has good rolling process adaptability and mechanical property.

Description

Steel bar resistant to corrosion in low-temperature atmospheric environment and production method thereof

Technical Field

The invention belongs to the technical field of hot-rolled steel bars, and particularly relates to a steel bar resisting corrosion in a low-temperature atmospheric environment and a production method thereof.

Background

Liquefied natural gas is stored at the temperature of-170 ℃, the inner layer of the storage tank is formed by welding low-temperature steel plates, the outer layer of the storage tank is formed by reinforced concrete, the storage tank is influenced by temperature change, and reinforcing steel bars for the outer layer concrete are easily corroded by external acidic liquid in the freezing and thawing process, so that the reinforcing steel bars in a reinforced concrete structure not only need to meet good low-temperature mechanical properties, but also need to have atmospheric corrosion resistance.

Corrosion of the steel reinforcement causes premature failure of the concrete structure and early withdrawal from service. The silicate cement concrete pore liquid presents high alkalinity, and the surface of the steel bar is oxidized to form a compact passive film in the high alkalinity pore liquid, so that the surface of the steel bar is prevented from being corroded and damaged. Because of the existence of carbon dioxide in the atmosphere, carbonic acid is formed when the carbon dioxide meets water, particularly at the present day of full development of the industry, a large amount of gas containing acidic substances in the air discharged by the industry forms a corrosive acidic solution along with rainwater, is attached to the surface of a concrete structure and permeates into the interior of the reinforced concrete structure, so that the alkalinity of pore liquid is reduced, the surface of a reinforced steel bar is blunt, and corrosion can be caused conditionally. Particularly, under the low-temperature atmospheric environment, with the loading and unloading of liquefied natural gas, due to the freezing and thawing effect, acidic liquid outside the concrete structure enters the concrete structure at a higher speed through the alternate cycle change of positive temperature and negative temperature of the environment, and the corrosion to the reinforcing steel bars is accelerated. Therefore, all countries in the world are actively researched, and at present, measures which are widely applied include stainless steel bars, coating steel bars, non-metal bars and the like, but the measures have different problems in wide application: stainless steel reinforcing steel bars are expensive, the corrosion resistant effect of the coating reinforcing steel bars is poor and satisfactory, and the mechanical properties of the non-metallic reinforcing steel bars are difficult to meet the requirements.

Disclosure of Invention

The invention provides a steel bar resisting corrosion in low-temperature atmospheric environment and a production method thereof, which are characterized in that in the aspects of component design and alloy element selection, in order to meet the requirement of corrosion resistance of the steel bar in the low-temperature environment, Cu and Sb are properly added on the basis of the low-temperature steel bar, and an online cooling control process in a hot rolling process is adjusted to inhibit an anodic dissolution reaction and a cathodic hydrogen evolution reaction of metal, reduce the corrosion current density and increase the charge transfer resistance of the metal, so that a steel bar product resisting corrosion in the low-temperature atmospheric environment is obtained, and the steel bar product is applied to the storage and transportation industry of liquefied natural gas, so that the steel bar product has excellent mechanical property and low-temperature durability.

In order to achieve the purpose, the invention adopts the following technical scheme:

the steel bar resisting corrosion in low temperature atmosphere environment comprises the following chemical components in percentage by weight: 0.08 to 0.12 percent of C, 0.20 to 0.40 percent of Si, 1.40 to 1.60 percent of Mn, less than or equal to 0.011 percent of P, less than or equal to 0.005 percent of S, 0.04 to 0.06 percent of Cr, 0.05 to 0.08 percent of V, 0.05 to 0.06 percent of Cu, 0.05 to 0.08 percent of Sb, and the balance of Fe and inevitable impurities.

The selection of the addition amount (weight percentage) of each element and the function description thereof are as follows:

c forms a compound cementite with iron. The carbon content in the steel is increased, the carburized body is large, the hardness and the strength of the steel are also improved, the plasticity and the toughness are reduced, and the welding performance is also deteriorated. Meanwhile, carbon is unfavorable for corrosion resistance of steel, and the addition amount of C in the steel bar is limited to 0.08-0.12%.

Si is added into steel as deoxidizer to increase the strength and hardness of steel, because the action is similar to that of C when the content of Si is large, the toughness of steel bar is reduced and the welding performance is deteriorated when the content of Si is too high, and the addition amount of Si is limited to 0.20-0.40%.

Mn is also added to steel as a deoxidizer to lower the plasticity and toughness of the steel, so that the content is appropriate, and the Mn component is defined as 1.40 to 1.60% in the present invention.

P and S are harmful elements which can reduce the plasticity and toughness of the steel, so that the smaller the content, the better.

Cr can form a compact oxide film on the surface of steel, thereby improving the passivation capability of the steel, and the Cr content of the invention is limited to 0.04-0.06%.

V can refine the grain size of ferrite and improve the strength and hardness of the structure. The growth of austenite grains is inhibited in the hot rolling process, thereby achieving the purposes of refining grains and improving performance. When the content of V is too high, on one hand, the production cost is increased, and on the other hand, coarse carbonitride is easily formed, so that the toughness and plasticity of the steel bar are reduced. In view of the performance objectives to be achieved by the present invention, V is added in an amount of 0.05% to 0.08%.

Cu has very excellent corrosion resistance and has an obvious effect of offsetting the harmful effect of S in steel, and the Cu component is 0.05-0.06 percent in the invention.

The addition of Sb can cause the formation of Sb on the metal surface₂O₅The compound of (1) has higher stability in a corrosion medium than a steel substrate, and is beneficial to preventing the metal substrate from being further corroded by the corrosion medium.

A production method of a steel bar resisting corrosion in a low-temperature atmospheric environment comprises the following steps:

1) the soaking temperature of the continuous casting billet is 1100-1150 ℃, and the heat preservation time is 1-1.5 hours;

2) the method comprises the following steps of cogging and rolling the continuous casting billet, wherein the cogging temperature is 1050-: after the rolled piece is subjected to medium rolling, fine grain control cooling is added before the rolled piece enters a finishing mill group, so that the rolled piece is cooled by 50-100 ℃; and a second stage: and (4) after the final rolling, controlling cooling to cool the rolled piece by 50-100 ℃, and finally, air-cooling the rolled piece to the cooling bed to room temperature.

Compared with the prior art, the invention has the beneficial effects that:

1) the invention fully considers that the use process of the steel bar in the service environment of low temperature (negative temperature) and normal temperature (positive temperature) reciprocating alternation is influenced by temperature change, the steel bar is more easily corroded by external acidic liquid in the freezing and thawing process, the acid corrosion resistance of the steel bar is improved by Cu and Sb elements, the atmospheric corrosion resistance of the low-temperature steel bar is improved, and the steel bar has good rolling process adaptability and mechanical property.

2) According to the invention, through reasonable optimization of each element component, the components are easy to stably control during smelting, the controlled cooling process is adjusted, and the fine grain cooling (pre-cooling) process before finish rolling is added, so that a product with more excellent performance is obtained. The corrosion resistance test of the obtained test steel bar shows that: the acid corrosion resistance of the low-temperature corrosion-resistant steel bar is obviously higher than that of the existing low-temperature steel bar, and the mechanical property of the low-temperature corrosion-resistant steel bar is stable.

Drawings

Figure 1 is a macroscopic topographical map of a comparative example with 3d immersion at pH 11.

Figure 2 is a macro topography of example 1 at pH 11 with week dip 3 d.

Figure 3 is a macroscopic topographical map of a comparative example with 3d immersion at pH 10.

Fig. 4 is a macro topography of example 1 at pH 10 for week 3 d.

Figure 5 is a macroscopic topographical map of a comparative example immersed at 5d, pH 11.

Fig. 6 is a macro topography of example 1 with week dip 5d, pH 11.

Fig. 7 is a macroscopic topography of a comparative example at pH 10 with week 5d immersion.

Fig. 8 is a macro topography of example 1 at pH 10 with week 5d immersion.

Detailed Description

The following examples are provided to further illustrate the embodiments of the present invention:

a production method of a steel bar resisting corrosion in a low-temperature atmospheric environment comprises the following steps:

1) the soaking temperature of the continuous casting billet is 1100-1150 ℃, and the heat preservation time is 1-1.5 hours; the temperature is beneficial to the homogenization of the components of the continuous casting billet, the overheating of the continuous casting billet or the bending of the continuous casting billet in a hearth can be caused by the overhigh temperature, the temperature of a steel bar is reduced when the continuous casting billet is rolled in the later stage due to the overlow temperature, the deformation resistance is increased, and the rolling specification is difficult to control.

2) The continuous casting billet is cogging-rolled, the initial rolling temperature is 1050-; and a second stage: and (3) after final rolling, controlling cooling to cool the rolled piece by 50-100 ℃, finally, air-cooling the rolled piece to room temperature in a cooling bed, packaging and warehousing, and ensuring the internal structure of the steel bar to be refined according to the two cooling modes so as to improve the strength and the hardness.

The following are the production processes corresponding to the respective chemical components of the examples and comparative examples of the present invention. Wherein, table 1 shows the specific component design of the comparative example and the steel bar example of the invention, table 2 shows the controlled cooling process of the hot rolling production of the comparative example and the steel bar example of the invention, table 3 shows the mechanical property test results of the comparative example and the steel bar example of the invention, and table 4 shows the corrosion rate test results of the comparative example and the steel bar example of the invention.

TABLE 1 specific chemical composition

TABLE 2 controlled Cooling Process conditions

TABLE 3 mechanical Property test results

TABLE 4 Corrosion resistance test results

Claims (1)

1. The reinforcing steel bar resistant to corrosion in low-temperature atmospheric environment is characterized by comprising the following chemical components in percentage by weight: 0.08 to 0.084 percent of C, 0.33 to 0.40 percent of Si, 1.40 to 1.57 percent of Mn, less than or equal to 0.011 percent of P, less than or equal to 0.005 percent of S, 0.04 to 0.06 percent of Cr, 0.05 to 0.08 percent of V, 0.05 to 0.06 percent of Cu, 0.05 to 0.08 percent of Sb, and the balance of Fe and inevitable impurities;

the production method of the steel bar resisting corrosion in the low-temperature atmospheric environment comprises the following steps:

1) the soaking temperature of the continuous casting billet is 1100-1150 ℃, and the heat preservation time is 1-1.5 hours;

2) the method comprises the following steps of cogging and rolling the continuous casting billet, wherein the cogging temperature is 1050-: after the rolled piece is subjected to medium rolling, fine grain control cooling is added before the rolled piece enters a finishing mill group, so that the rolled piece is cooled by 50-100 ℃; and a second stage: and (4) after the final rolling, controlling cooling to cool the rolled piece by 50-100 ℃, and finally, air-cooling the rolled piece to the cooling bed to room temperature.

Images