CN114959451A - Weather-resistant and fire-resistant structural steel for south-sea marine environment - Google Patents

Abstract

The invention relates to the field of low alloy steel, in particular to weather-resistant and fire-resistant structural steel for a south-sea marine environment. The structural steel comprises the following chemical components in percentage by weight: c: less than or equal to 0.12 percent; si: 0.1-0.3%; mn: 0.5-1.7%; p: less than or equal to 0.06 percent; s: less than or equal to 0.003 percent; nb: 0.01-0.04%; ti: less than or equal to 0.03 percent; mo: less than or equal to 0.4 percent; cr: 0.1-0.5%; ni: 0.2-0.5%; cu: 0.2-0.5%; b: 0 to 0.003%; less than 0.02% of Als and the balance of Fe. The strength grade of the low alloy steel can reach 460MPa, and compared with the common Q460 steel, the low alloy steel has excellent fire resistance and corrosion resistance, and the corrosion rate is reduced by 5-15%. The performance is excellent, and the paint can be widely applied to the fields of buildings, bridge construction or traffic transportation and has good application value.

Description

A weathering and refractory structural steel for South China Sea marine environment

technical field

The invention relates to the field of low-alloy steel, in particular to a weather-resistant and refractory structural steel for the South China Sea marine environment.

Background technique

Steel materials are widely used in aerospace, bridges, automobiles, ships and other fields, and steel structures exposed to the outdoors are generally subject to atmospheric corrosion in the atmospheric environment. Corrosion is not only a safety issue, an ecological civilization issue, but also an economic issue. According to statistics, the total cost of corrosion in my country accounts for about 3% to 4% of the GDP of that year. Atmospheric corrosion is one of the most numerous, most extensive and most destructive types of metal corrosion. Therefore, the research and development of weathering steel is of great significance. Corrosion is the result of the joint action of materials and the environment. Under the premise that environmental factors cannot be changed, the corrosion resistance of materials can only be improved by changing the composition, organization and structure of materials. Weathering steel, that is, low-alloy atmospheric corrosion-resistant steel, is based on low-carbon steel to improve its atmospheric corrosion resistance by adding a small amount of alloying elements Cu, Cr, Ni, P, Mn, Sn, etc. At present, due to the continuous expansion of the application field of weathering steel, more types of weathering steel need to be developed to meet the needs of time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a weather-resistant and refractory structural steel for the South China Sea marine environment with a new composition, which has excellent corrosion resistance to the South China Sea marine atmosphere and has a good corrosion resistance effect.

The technical scheme of the present invention is:

A weather-resistant and refractory structural steel for the marine environment of the South China Sea, comprising the following chemical components by mass: C: ≤ 0.12%; Si: 0.1-0.3%; Mn: 0.5-1.7%; P: ≤ 0.06%; S: ≤ 0.003% ;Nb:0.01～0.04%;Ti:≤0.03%;Mo:≤0.4%;Cr:0.1～0.5%;Ni:0.2～0.5%;Cu:0.2～0.5%;B:0～0.003%;Als＜ 0.02%, the balance is Fe.

The weather-resistant and refractory structural steel for the South China Sea marine environment includes the following chemical components by mass percentage: C: 0.05-0.07%; Si: 0.15-0.30%; Mn: 0.9-1.1%; P: 0.015-0.025%; S: ≤0.002%; Nb: 0.01-0.025%; Ti: 0.01-0.02%; Mo: 0.2-0.4%; Cr: 0.2-0.5%; Ni: 0.3-0.5%; Cu: 0.2-0.35%; B: 0.001- 0.003%; Als<0.01%, the balance is Fe.

Compared with ordinary Q460MPa grade steel, the weathering and refractory structural steel for the South China Sea marine environment has a corrosion rate reduced by 5% to 15%.

The weather-resistant and refractory structural steel for the marine environment of the South China Sea is used in the fields of building, bridge construction or vehicle manufacturing, and is used in bare or painted areas in hot and humid areas.

The weather-resistant and refractory structural steel used in the marine environment of the South China Sea has a strength of 460MPa, which is higher than that of ordinary Q460 steel at high temperature. 2/3 of the strength at room temperature, more than 3 times the tensile strength of ordinary Q460 steel in 600 ℃ environment for 2 hours.

The advantages and beneficial effects of the present invention are:

1. The present invention provides a new composition of 460MPa grade corrosion-resistant refractory steel for the South China Sea marine environment. Compared with ordinary Q460 steel, its corrosion rate is reduced by 5% to 15%, and excellent atmospheric corrosion resistance is achieved. The weathering steel of the present invention can be used bare or lightly painted in hot and humid environments, with less maintenance cost in the later period, long product life, and reduced full-cycle use cost.

2. The present invention can be widely used in the fields of building, bridge construction or vehicle manufacturing, and has good application value. The high temperature (600 DEG C, 2 hours) tensile strength of the 460MPa grade South China Sea marine environment steel of the present invention is more than three times that of ordinary Q460 steel.

Description of drawings

Fig. 1 is the corrosion rate curve of the comparative example and the embodiment under the simulated atmospheric environment.

Detailed ways

In the specific implementation process, the weather-resistant and refractory structural steel for the South China Sea marine environment of the present invention includes the following chemical components by mass: C: ≤ 0.12%; Si: 0.1-0.3%; Mn: 0.5-1.7%; P: ≤ 0.06% ;S:≤0.003%;Nb:0.01～0.04%;Ti:≤0.03%;Mo:≤0.4%;Cr:0.1～0.5%;Ni:0.2～0.5%;Cu:0.2～0.5%;B:0 ~0.003%; Als<0.02%, the balance is Fe.

The composition design ideas of the above-mentioned weather-resistant and refractory structural steel for the South China Sea marine environment are:

C is an effective strengthening element in steel. Increasing the C content is conducive to improving the strength, but too high carbon content will precipitate carbide particles and reduce plasticity and toughness. At the same time, too high carbon content also affects the welding and stamping properties of steel. Therefore, the present invention designs C≤0.12wt%, and preferably C: 0.05-0.07wt%.

In iron and steel metallurgy, Si can play a similar role as P, and can reduce the γ-phase region and form a γ-phase circle, which is second only to P in the solid solution strengthening effect of ferrite. Si can also improve the resistivity of steel and enhance the corrosion resistance of steel under natural conditions. It can synergize with other alloying elements (such as Cu, Cr, P, Ni, etc.) to improve the corrosion resistance of steel, but too high content of Si will make it difficult to remove phosphorus during rolling, and will also lead to a decrease in welding performance. Therefore, the present invention designs Si: 0.1-0.3 wt %, preferably Si: 0.10-0.20 wt %.

Mn has a strong solid solution strengthening effect, which can significantly reduce the phase transition temperature of steel and refine the microstructure of steel. It is an important strengthening and toughening element. At the same time, many scholars believe that Mn can improve the resistance of steel in marine atmosphere. It is corrosive and exists in the form of MnFe ₂ O ₄ in the rust layer. However, too much Mn makes slab cracks easy to occur in the casting process, and also reduces the weldability of the steel. Therefore, the present invention relates to Mn: 0.5-1.7 wt%, preferably Mn: 0.9-1.1 wt%.

Appropriate P content can significantly improve the atmospheric corrosion resistance of steel, and when P and Cu are jointly added to steel, a better synergistic weathering effect is exhibited. However, too high P content will significantly reduce the plasticity and low temperature toughness of steel. Therefore, the present invention designs P: ≤ 0.06 wt %, preferably P: 0.015-0.025 wt %.

S is an element with poor weather resistance, and its content is controlled to be 0.04 wt % or less as a residual element. Therefore, the present invention designs S:≤0.003wt%, preferably S:≤0.002wt%.

Nb is not only a strong ferrite forming element, but also a strong carbonitride, and it is easy to form metal compounds when heated for a long time, which can strengthen the mechanical properties and refine the grains. In high temperature applications, Nb can replace part of Mo, reducing cost. Therefore, the present invention designs Nb: 0.01-0.04wt%, preferably Nb: 0.01-0.025wt%.

Ti is also one of the strong carbide forming elements and one of the strong ferrite forming elements, which can significantly improve the plasticity and toughness of low alloy steels. Titanium-containing alloy structural steel has good mechanical properties and process properties, but the main disadvantage is that the hardenability is slightly poor. Therefore, the present invention designs Ti: ≤ 0.03%, preferably Ti: 0.01-0.02%.

Mo can improve hardenability and thermal strength in steel, prevent temper brittleness, increase remanence and coercivity and corrosion resistance in certain media. Since Mo increases the softening and recovery temperature and recrystallization temperature after deformation strengthening, and strongly improves the creep resistance of ferrite, it effectively inhibits the aggregation of cementite at 450-600 °C, and promotes the precipitation of special carbides. The most effective alloying element for improving the thermal strength of steel. But Mo is expensive and uses higher ingredients. Therefore, the present invention designs Mo: ≤ 0.4 wt %, preferably Mo: 0.2-0.4 wt %.

Cr can increase the hardenability of steel and has a secondary hardening effect, which can improve the hardness and wear resistance of high carbon steel without making the steel brittle; when the content is high, the steel has good high temperature oxidation resistance and oxidation resistance It also increases the thermal strength of steel, and Cr is the main alloying element of stainless and corrosion-resistant steel and heat-resistant steel. Therefore, the present invention designs Cr: 0.1-0.5%, preferably Cr: 0.2-0.5%.

Ni strengthens the ferrite and refines the pearlite in the steel, the overall effect is to increase the strength, and the effect on the plasticity is not significant. With the increase of Ni content, the yield strength of steel increases faster than the tensile strength, so the yield of Ni-containing steel is higher than that of ordinary carbon steel. While improving the strength of steel, nickel has less damage to the toughness, plasticity and other process properties of steel than other alloying elements. When the Ni content is high, the performance of steel against marine atmospheric corrosion can be significantly improved. . Therefore, the present invention designs Ni: 0.2-0.5%, preferably Ni: 0.3-0.5%.

The prominent role of Cu in steel is to improve the atmospheric corrosion resistance of ordinary low-alloy steel, especially in combination with P. The addition of Cu also increases the strength and yield ratio of the steel without adversely affecting the weldability. When the Cu content exceeds 0.75wt%, the aging strengthening effect can be produced after solution treatment and aging, but when the content is high, it is unfavorable for thermal deformation and leads to copper embrittlement during hot working. Therefore, the present invention designs Cu: 0.2-0.5%, preferably Cu: 0.2-0.35%.

The main function of B in steel is to increase the hardenability of steel, thereby saving other rarer metals, such as nickel, chromium, molybdenum, etc. For this purpose, its content is generally specified at 0.001-0.005wt%. Therefore, the present invention designs B: 0 to 0.003%, preferably B: 0.001 to 0.003%.

Based on the above-mentioned preferred components, the corrosion rate of the 460MPa grade corrosion-resistant refractory steel for the South China Sea marine environment of the present invention is reduced by 5% to 15% compared with ordinary Q460 steel.

Based on the excellent corrosion resistance of the above-mentioned corrosion-resistant refractory steel for the marine environment of the South China Sea, the present invention also provides a use of the above-mentioned 460MPa grade corrosion-resistant refractory steel. installed to use.

The invention has good high temperature performance, and the tensile strength after 2 hours in the environment of 600 DEG C is ≥327MPa, which is higher than 2/3 of the strength at normal temperature. The tensile strength of ordinary Q460 steel after 2 hours in 600 ℃ environment is less than or equal to 105MPa.

The present invention will be further described in detail below through the examples, but the protection scope of the present invention is not limited to the scope of the described examples.

Examples and Comparative Examples

The specific components of the corrosion-resistant and refractory steel of the present invention and Comparative Example 1 (ordinary weathering steel Q460) are shown in Table 1. The 460MPa grade corrosion-resistant refractory steel was prepared by conventional smelting and controlled rolling and controlled cooling processes. According to ISO 16539-2013, the examples and comparative examples were subjected to indoor dry-wet alternate accelerated simulation experiments to compare their corrosion resistance with ordinary weathering steel Q460. . The specific experimental steps are as follows:

(1) Weigh the initial mass of the sample, the analytical balance used is Sartorius BS 224S, and its precision is: d=0.1 mg;

(II) Put the test sample into the PR-2KP constant temperature and humidity test chamber for 30 minutes to pre-humidify, the temperature in the test chamber is 35°C, and the relative humidity is 90%;

(III) The test sample is taken out of the test box, and the corrosion simulated liquid is added dropwise to its surface by 40 μL/cm ² to make it spread evenly, wherein the simulated marine environment used in this test is the NaCl aqueous solution with a concentration of 3wt%, and the required time is about 10 minute;

(IV) Put the test sample back into the test chamber again for 344 minutes, i.e. ensure that the total time of the first stage is 6.4 hours, and this process simulates a high temperature and high humidity environment;

(V) Through program setting, the temperature of the chamber of the test box is controlled at 40° C., the relative humidity is 40%, and the duration is 1.6 hours, and this process simulates a dry environment. The total time above is 8 hours, representing a test cycle, and the ratio of wet to dry environment time is 4:1, simulating the marine atmospheric corrosion environment of the South China Sea with a relative humidity of 80%.

(VI) After every 3 test cycles, i.e. after 24 hours, take out the test sample and wash the salt with distilled water to avoid the accumulation of salt particles on the surface of the test sample, repeat steps (III), (IV) and ( V) step until the set dry and wet alternate cycle. The test period is 30 days, a total of 720 hours, and the time of corrosion weight loss measurement is: 120, 240, 360, 480, 600 and 720 hours, a total of 6 measurements.

The average corrosion rate was obtained from the corrosion weight loss per unit area of the three test samples. Furthermore, the reduction amount of the corrosion rate of the Example with respect to the comparative example was calculated|required.

Table 1 Chemical composition of three high-strength weathering steels (wt.%)

As shown in Figure 1, it can be seen from the average corrosion rate curves of the examples (Q460-1 and Q460-2) and the comparative example (Q460) that the corrosion rates of the three steels all show a trend of increasing first and then decreasing: In the first 240h, the corrosion rate of Q460-2 steel is the fastest, followed by Q460-1, and the corrosion rate of Q460 steel is the slowest; but after 360h, the corrosion rate of Q460-1 steel decreases rapidly, and the corrosion rate is significantly lower than that of the other two steels, which is resistant to atmospheric corrosion Best performance.

To sum up, the 460MPa grade corrosion-resistant refractory steel of the present invention has a low-alloy steel strength grade of up to 460MPa, which has excellent refractoriness and corrosion resistance compared with ordinary Q460 steel, and its corrosion rate is reduced by 5% to 15%. . As a result, excellent atmospheric corrosion resistance can be achieved. The product can be used bare in hot and humid areas, reducing painting costs and environmental pollution. It can be widely used in construction, bridge construction, transportation or vehicle manufacturing. It has a good application prospect. .

Claims (5)

1. The weather-resistant and fire-resistant structural steel for the south-sea marine environment is characterized by comprising the following chemical components in percentage by mass: c: less than or equal to 0.12 percent; si: 0.1-0.3%; mn: 0.5-1.7%; p: less than or equal to 0.06 percent; s: less than or equal to 0.003 percent; nb: 0.01-0.04%; ti: less than or equal to 0.03 percent; mo: less than or equal to 0.4 percent; cr: 0.1-0.5%; ni: 0.2-0.5%; cu: 0.2-0.5%; b: 0 to 0.003%; less than 0.02% of Als and the balance of Fe.

2. The weather-resistant and fire-resistant structural steel for the south sea marine environment as claimed in claim 1, comprising the following chemical components in percentage by mass: c: 0.05-0.07%; si: 0.15-0.30%; mn: 0.9-1.1%; p: 0.015-0.025%; s: less than or equal to 0.002 percent; nb: 0.01 to 0.025%; ti: 0.01-0.02%; mo: 0.2-0.4%; cr: 0.2-0.5%; ni: 0.3-0.5%; cu: 0.2-0.35%; b: 0.001 to 0.003%; less than 0.01 percent of Als and the balance of Fe.

3. The weather-resistant and fire-resistant structural steel for the marine environment in the south China sea according to claim 1 or 2, wherein the corrosion rate of the weather-resistant and fire-resistant structural steel is reduced by 5% to 15% compared to that of ordinary Q460MPa grade steel.

4. The weather-resistant and fire-resistant structural steel for the south-sea marine environment according to claim 1 or 2, wherein the weather-resistant and fire-resistant structural steel is applied to the fields of buildings, bridge construction or vehicle manufacturing, and is used in a naked state or coated state in hot and humid areas.

5. The weather-resistant and fire-resistant structural steel for the south-sea marine environment as claimed in claim 1 or 2, wherein the strength of the weather-resistant and fire-resistant structural steel reaches 460MPa, the high-temperature strength is higher than that of ordinary Q460 steel, the tensile strength after 2 hours at 600 ℃ is not less than 327MPa, and is higher than 2/3 of the normal-temperature strength, and the tensile strength is more than 3 times of that of ordinary Q460 steel after 2 hours at 600 ℃.

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