CN114959483B

CN114959483B - Weather-resistant steel resistant to wet heat and high in salinity marine atmospheric environment and production method thereof

Info

Publication number: CN114959483B
Application number: CN202210623823.4A
Authority: CN
Inventors: 严翔; 官计生; 杨治争
Original assignee: Wuhan Iron and Steel Co Ltd
Current assignee: Wuhan Iron and Steel Co Ltd
Priority date: 2022-06-02
Filing date: 2022-06-02
Publication date: 2023-06-16
Anticipated expiration: 2042-06-02
Also published as: CN114959483A

Abstract

The invention belongs to the technical field of weathering steel, and discloses weathering steel resistant to damp-heat and high-salinity marine atmospheric environment and a production method thereof, wherein the weathering steel comprises the following components in percentage by mass: c:0.02% -0.06%, si:0.17% -0.37%, mn:0.8% -1.2%, P: less than or equal to 0.012 percent, S: less than or equal to 0.005 percent, cu:0.8% -1.2%, cr:0.2% -0.4%, ni:1.5% -2%, mo:0.1% -0.25%, ti:0.01% -0.03%, sn:0.05% -0.2%, and the balance of Fe and unavoidable impurities. According to the invention, through optimizing the chemical components of the steel and combining the controlled rolling and controlled cooling preparation process, the weather-resistant steel has excellent comprehensive mechanical properties, and simultaneously has excellent economical efficiency and corrosion resistance, and is more suitable for resisting hot and humid marine atmospheric environments such as south China sea and the like.

Description

Weather-resistant steel resistant to wet heat and high in salinity marine atmospheric environment and production method thereof

Technical Field

The invention belongs to the technical field of weather-resistant steel, and particularly relates to weather-resistant steel for a damp-heat resistant high-salinity marine atmospheric environment and a production method thereof.

Background

Since the beginning of the twentieth century, the atmospheric corrosion and protection of steel has become an important research area, and the development of weathering steel used in different environments has been continuously carried out all over the world. The weathering steel is low alloy high strength steel with good corrosion resistance in the atmosphere by adding a small amount of alloy elements. The weather-resistant steel has the atmospheric corrosion resistance which is 2-8 times that of the common carbon steel, and the longer the service time is, the more outstanding the corrosion resistance is, and the weather-resistant steel also has the excellent performances of mechanics, welding and the like, so that the weather-resistant steel can be widely applied to the fields of construction, ships, railways and the like.

Atmospheric environments are generally classified into four types, including rural, urban, industrial and marine, depending on the type of contaminants contained therein, with marine atmosphere being most corrosive. The ocean atmosphere is entrained with a large amount of salt particles, and the salt particles fall on the surface of the steel structure to generate electrolyte films due to deliquescence, and the micro-battery reaction of atmospheric corrosion is promoted due to the fact that salt is dissolved in the liquid films to increase the conductivity of the electrolyte and destroy the protection of corrosion products, so that the corrosion process is greatly accelerated.

Among the existing marine weathering steel systems, 3Ni steel is favored for its excellent resistance to marine atmospheric corrosion. The 3Ni steel is produced in Japan, and the traditional Cu-P series weathering steel is difficult to generate a protective rust layer in the marine atmospheric environment because the Japan region has typical marine atmospheric environment characteristics, so that the corrosion rate cannot be effectively reduced, and in order to develop the high-strength weathering steel suitable for the marine atmospheric environment, the Japan provides the high-Ni series weathering steel with the nickel mass fraction of 3 percent, and initial test results show that the steel has excellent corrosion resistance in coastal atmosphere.

Compared with overseas countries, china has a later development and start of ocean weather-resistant steel, south China sea belongs to a typical wet and hot high-salt ocean atmospheric environment, namely high temperature, high humidity, high salt mist and strong radiation, and the corrosion classification and classification of the area exceeds the highest C5 level, so that the problem of material corrosion is very remarkable. Although the corrosion resistance of the 3Ni steel developed in Japan is superior to that of the traditional weathering steel, the nickel resource reserves in China are relatively deficient, the wide application of the steel is limited by the high price caused by the high Ni content, and the natural environment of the south China sea is more severe, and the applicability of the 3Ni steel is also under test, so that the weathering steel suitable for the humid and hot high-salinity marine atmospheric environment of the south China sea is independently developed, and the economy is considered while the corrosion resistance is ensured.

Disclosure of Invention

Aiming at the defects of the existing high-Ni weather-resistant steel, the invention provides the weather-resistant steel with the functions of moisture resistance, heat resistance and high salinity, which is more suitable for resisting the hot and humid marine atmospheric environment such as the south sea and the like, and the production method thereof.

In order to solve the technical problems, the invention provides weather-resistant steel for the ocean atmospheric environment with moisture resistance and heat resistance and high salinity, which comprises the following components in percentage by mass: c:0.02% -0.06%, si:0.17% -0.37%, mn:0.8% -1.2%, P: less than or equal to 0.012 percent, S: less than or equal to 0.005 percent, cu:0.8% -1.2%, cr:0.2% -0.4%, ni:1.5% -2%, mo:0.1% -0.25%, ti:0.01% -0.03%, sn:0.05% -0.2%, and the balance of Fe and unavoidable impurities.

Further, the mass ratio of Ni to Cu is greater than 1.3.

Preferably, the mass percentage of C is 0.025% -0.055%.

Preferably, the mass percentage of Si is 0.2% -0.3%.

Preferably, the mass percentage of Mn is 0.9% -1.1%.

Preferably, the mass percentage of Cu is 0.9% -1.1%.

Preferably, the mass percentage of Cr is 0.25% -0.35%.

Preferably, the mass percentage of Ni is 1.6% -1.9%.

Preferably, the mass percentage of Mo is 0.15% -0.25%.

Preferably, the mass percentage of Sn is 0.08-0.16%.

In the scheme, the humidity of the hot and humid high-salinity marine atmospheric environment is 65-75%, the temperature is 40-50 ℃, and the salinity content is 3.2-3.8%.

The invention also provides a production method of the weather-resistant steel for the damp-heat resistant high-salinity marine atmospheric environment, which comprises the following steps:

1) Smelting and casting blank: smelting and refining the components of the weathering steel in a converter or an electric furnace according to the mass percentage of the weathering steel, and then continuously casting the blank;

2) Heating a casting blank: heating the continuous casting billet at 1150-1200 ℃;

3) Rolling: rolling the continuous casting billet in two stages in an austenite single-phase region, wherein the final rolling temperature is 790-860 ℃, and a rolled steel plate is obtained;

4) And (3) cooling: and (3) cooling the steel plate, wherein the cooling temperature is 760-800 ℃, the cooling speed is 10-30 ℃/s, the final cooling temperature is 350-450 ℃, and then the steel plate is air-cooled to room temperature to obtain the weathering steel.

In the scheme, the yield strength of the weathering steel is more than or equal to 400MPa, the tensile strength is more than or equal to 500MPa, the elongation is more than or equal to 20%, the yield ratio is less than or equal to 0.8, and the impact energy at-20 ℃ is more than or equal to 100J.

The components and the content ranges thereof are mainly based on the following principles:

c: the invention adopts the component design thought of ultra-low carbon, has lower C content, and can improve the weldability and the toughness and plasticity on one hand; on the other hand, the method is favorable for obtaining a single acicular ferrite microstructure, avoiding the formation of larger-sized carbide, and achieving the purpose of effectively avoiding the formation of micro couples and improving the corrosion resistance. Therefore, the content thereof is controlled to be in the range of 0.02% to 0.06%, preferably 0.025% to 0.055%.

Si: is a common steelmaking deoxidizer and solid solution strengthening element, on one hand, can effectively refine alpha-FeOOH in the rust layer, thereby effectively inhibiting the further development of corrosion; on the other hand, too high a Si content is detrimental to weldability. Thus, the content of the modified starch is controlled to be in the range of 0.17% -0.37%, preferably 0.2% -0.3%.

Mn: the corrosion resistance of the steel in the ocean atmosphere can be improved besides improving the strength and toughness of the steel, and the Mn content is improved in order to compensate the corrosion resistance reduction caused by Ni reduction; however, too high Mn tends to form Mn segregation and strip-like MnS inclusions, which are detrimental to toughness and corrosion resistance of the steel. Therefore, the content of the modified starch is controlled to be in the range of 0.8% -1.2%, preferably 0.9% -1.1%.

P: the steel is one of the cheapest alloy elements adopted in the design of weathering steel, and the steel is mainly used for marine building structures, and has higher requirements on the strength and toughness and welding performance of the steel plate, so that the steel does not adopt P element as a corrosion resistant alloy element, the lower the P content in the steel is hopefully, the better the lower the P content is, but the P content is controlled to be less than or equal to 0.012 percent in consideration of smelting production cost and other reasons.

S: the content of S is limited to be less than or equal to 0.005%, which is a harmful impurity element in steel, reduces toughness and weldability of steel, but if the content is limited to be too low, the production difficulty is increased, and the production cost is increased.

Cu: cu and Ni have better cooperative protection effect, and the enrichment of Cu in the rust layer in the weathering steel can reduce the corrosion acceleration of chloride ions to steel, and the protection of the rust layer to the steel matrix is enhanced by improving the polarization resistance in the steel corrosion electrochemical process, so that the marine atmospheric corrosion resistance is improved. In order to compensate for the corrosion resistance reduction caused by Ni reduction, the Cu content in the steel is improved to be in the range of 0.8-1.2%, preferably 0.9-1.1%.

Cr: the Cr element is generally considered to improve the compactness and stability of the rust layer through the stabilization of alpha-FeOOH and the refinement of the crystal grains of the rust layer, so that the penetration of chloride ions and sulfate ions is effectively prevented, and the purpose of 'rust production with rust' is achieved; however, the composition design of high Cr has better corrosion resistance to industrial atmospheric environment, but the corrosion resistance effect is not outstanding to marine climate, and the alloy cost is higher. The invention is controlled to be in the range of 0.2% -0.4% and preferably 0.25% -0.35% from the two aspects of economy and corrosion resistance.

Ni: the alloy element is a key alloy element for improving the marine atmospheric corrosion resistance of the steel plate, and a certain amount of Ni element is added into the steel, so that a stable, compact and chloridion corrosion-resistant peeled amorphous layer can be formed on the surface of the steel, grains of the inner rust layer are thinned, the compactness of the inner rust layer is improved, and the marine atmospheric corrosion resistance is improved; however, too high Ni content greatly increases the manufacturing cost of the steel, and the content is controlled to be in the range of 1.5% -2%, preferably 1.6% -1.9% in consideration of balance point of low-cost mass production and corrosion protection.

Mo: the main purpose of micro Mo alloying is to form Mo in the rust layer by Mo ₄ ^2- Promoting the inner rust layer to have cation selectivity, thereby electrochemically inhibiting the invasion of chloride ions and improving the corrosion resistance of the steel; however, too high a Mo content not only greatly increases the alloy cost, but also increases the hardenability of the steel, which is disadvantageous for the welding performance. Therefore, the invention comprehensively considers the economical efficiency and the corrosion resistance, and the content is controlled to be in the range of 0.10-0.25%, preferably 0.15-0.25%.

Ti: the main purpose of micro Ti alloying is to improve the low-temperature toughness of the structural steel welding HAZ to improve the welding performance and simultaneously effectively inhibit the content of Cl ^- And the formation and crystallization of a key product beta-FeOOH in the environment refine the crystal grains of the rust layer and improve the corrosion resistance. The invention comprehensively considers the economical efficiency and the comprehensive performance, and controls the content thereof within the range of 0.01-0.03 percent.

Sn: the trace Sn element is added into the steel, and a continuous film layer containing tin oxide and copper oxide is formed on the surface of the steel by mainly utilizing the good synergistic effect of Sn, cu and other elements, so that the corrosion resistance of the steel is improved. Considering that an excessively high Sn content may impair the toughness of the steel, the content thereof is controlled to be in the range of 0.05% to 0.20%, preferably 0.08% to 0.16%.

Ni/Cu ratio: cu in steel is selectively oxidized due to surface Fe during heating, so that a low-melting-point Cu-rich phase is easily formed at the interface between the surface and an oxide layer, and a liquid Cu phase is formed at a heating temperature and penetrates along an austenite grain boundary, so that surface cracks are generated during hot working. To prevent rolling defects caused by the presence of liquid-phase Cu and improve the low-temperature toughness of steel, the Ni/Cu ratio is controlled to be greater than 1.30.

The main technological parameters of the production method of the invention are as follows:

heating temperature of casting blank: 1150-1200 deg.c, and may be used in ensuring the complete solid solution of trace alloy elements and preventing austenite grains from becoming coarse. On one hand, the continuous casting billet is not heated thoroughly, alloy elements cannot be fully dissolved and diffused, and the component uniformity of the steel plate is affected; on the other hand, too low a heating temperature of the casting blank will result in a reduction of the start rolling temperature and finish rolling temperature, so that the rolling resistance of the steel is increased, and the requirement of large production equipment cannot be met. On one hand, austenite grains become coarse, the coarse original austenite grains increase the difficulty of rolling refined austenite grains, and the final mechanical properties of the steel are not good; on the other hand, the excessively high heating temperature can increase the thickness of the oxide scale on the surface layer of the casting blank so as to increase the difficulty of descaling and influence the surface quality of the steel plate.

Rolling and cooling control: the control of the rolling process parameters can promote the refinement of ferrite to achieve the best comprehensive performance; the control of the cooling process parameters can improve the structure morphology of the steel, refine the austenite structure, prevent or delay the early precipitation of carbide in the cooling process, ensure that carbide is dispersed and precipitated in ferrite, improve the strength and improve the comprehensive mechanical property of the steel. By implementing the controlled rolling and cooling process, the microstructure mainly comprising fine acicular ferrite is obtained, and the strength and toughness matching performance and corrosion resistance of the steel plate are obviously improved.

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

1) Compared with the existing high-Ni weather-resistant steel, the invention optimizes the chemical components of the steel, reduces the content of noble metal elements Ni and Cr so as to reduce the manufacturing cost of the steel, improves the content of Cu and Mn so as to compensate the corrosion resistance reduction caused by the reduction of Ni and Cr, limits the Ni/Cu ratio so as to improve the toughness of the steel, and adds a small amount of corrosion-resistant alloy elements such as Ti, mo, sn and the like to further improve the corrosion resistance and mechanical property of the steel, so that the weather-resistant steel has better economical efficiency and corrosion resistance, reduces the cost by nearly 20 percent compared with 3Ni steel, has better corrosion resistance level, and is more suitable for resisting the hot humid and high-salinity marine atmospheric environment such as the south China sea and the like.

2) The invention obtains the microstructure mainly comprising fine acicular ferrite through the implementation of the controlled rolling and cooling process, further improves the comprehensive mechanical property of the steel, and obtains the weather-resistant steel with the yield strength of more than or equal to 400MPa, the tensile strength of more than or equal to 500MPa, the elongation of more than or equal to 20%, the yield ratio of less than or equal to 0.8, the impact energy of less than or equal to 100J at minus 20 ℃, and has excellent strength and toughness matching property and welding property, thus being applicable to the construction of marine building structures.

Detailed Description

For a better understanding of the present invention, the following examples are further illustrated, but are not limited to the following examples.

Examples 1 to 3

The components and mass percentages of the weather resistant steel in examples 1-3 are shown in Table 1:

TABLE 1

Note that: "/" indicates that no additive was added, and the comparative example was 3Ni steel.

The production method of the weather resistant steel with the moisture and heat resistance and the high salinity in the marine atmospheric environment in the embodiments 1-3 comprises the following steps:

3) Rolling: rolling the continuous casting blank in two stages in a slow high-speed rolling mode in an austenite single-phase region, wherein the final rolling temperature is 790-860 ℃ to obtain a rolled steel plate;

The main technological parameters of the production method are shown in Table 2:

TABLE 2

The overall mechanical properties of the weathering steels of examples 1-3 are shown in Table 3:

TABLE 3 Table 3

As can be seen from Table 3, the yield strength of the weathering steel prepared by the invention reaches 400MPa, and the weathering steel has excellent strength-toughness matching performance and welding performance,

periodic infiltration corrosion tests simulating a high salt atmosphere environment in south China sea were carried out on the weathering steels of examples 1 to 3 and the Ni steel of comparative example 3 according to TB/T2375-1993 method for periodic infiltration corrosion test of weathering steels for railway, and the test parameters were set as follows: the infiltration solution is NaCl solution with the mass fraction of 3.5%, the temperature is 45 ℃, the humidity is 70%, each cycle period is 60min (12 min of soaking and 48min of illumination), the test period is 24h, 48h, 72h and 96h, and the test results are shown in Table 4:

TABLE 4 Table 4

Note that: the relative corrosion rate was based on comparative example 3Ni steel.

As can be seen from Table 4, the weathering steel prepared by the present invention has lower corrosion rate in 3.5% NaCl solution than 3Ni steel and better corrosion resistance level.

Comparing the costs of the weathering steels of examples 1-3 and the comparative example 3Ni steel, the alloy costs of examples 1, 2 and 3 weathering steels are 80.9%, 80.1% and 73.8% of the comparative examples, respectively, so as to achieve the purpose of reducing the cost.

The above examples are presented for clarity of illustration only and are not limiting of the embodiments. Other variations or modifications of the above description will be apparent to those of ordinary skill in the art, and it is not necessary or exhaustive of all embodiments, and thus all obvious variations or modifications that come within the scope of the invention are desired to be protected.

Claims

1. The weather-resistant steel for the marine atmospheric environment with the moisture and heat resistance and the high salinity is characterized by comprising the following components in percentage by mass: c:0.02% -0.06%, si:0.17% -0.37%, mn:0.8% -1.2%, P: less than or equal to 0.012 percent, S: less than or equal to 0.005 percent, cu:1.1% -1.2%, cr:0.2% -0.25%, ni:1.6% -2%, mo:0.1% -0.25%, ti:0.01% -0.03%, sn:0.16% -0.2%, the balance being Fe and unavoidable impurities, and the mass ratio of Ni to Cu is more than 1.3; the humidity of the damp-heat high-salinity marine atmospheric environment is 65-75%, the temperature is 40-50 ℃, and the salinity content is 3.2-3.8%;

the production method of the weathering steel comprises the following steps:

4) And (3) cooling: and cooling the rolled steel plate, wherein the cooling temperature is 760-800 ℃, the cooling speed is 10-30 ℃/s, the final cooling temperature is 350-450 ℃, and then the steel plate is air-cooled to room temperature to obtain the weathering steel.

2. The weather resistant steel for a wet heat resistant high salinity marine atmosphere according to claim 1, wherein the yield strength of the weather resistant steel is not less than 400MPa, the tensile strength is not less than 500MPa, the elongation is not less than 20%, the yield ratio is not more than 0.8, and the impact energy at-20 ℃ is not less than 100J.

3. A method for producing the weather resistant steel for hot and humid marine atmosphere according to any one of claims 1 to 2, characterized by comprising the steps of: