阅读说明：本技术 660MPa级高耐蚀耐候钢及其制备方法 (660 MPa-grade high-corrosion-resistance weathering steel and preparation method thereof ) 是由 崔凯禹 李正荣 靳阳 汪创伟 张开华 姚永国 于 2020-07-29 设计创作，主要内容包括：本发明属于钢铁冶金技术领域,具体涉及660MPa级高耐蚀耐候钢及其制备方法。本发明所要解决的技术问题在于提供具有良好耐腐蚀作用的高耐蚀耐候钢。其化学成分为：C≤0.12％,Si：2.20～3.00％,Mn≤1.50％,P：0.060～0.150％,S≤0.015％,Cr：2.90～3.70％,Ni：0.10～0.40％,Cu：0.20～0.60％,Als≥0.010％,余量为Fe及不可避免的杂质。本发明高耐蚀耐候钢耐大气腐蚀性指数I达到14.10～15.51,显著高于6.0,实现了产品优良的耐大气腐蚀性能,可在炎热潮湿地区裸露使用,广泛用于建筑、桥梁施工或车辆制作领域,具有良好的应用价值。(The invention belongs to the technical field of ferrous metallurgy, and particularly relates to 660MPa grade high-corrosion-resistance weathering steel and a preparation method thereof. The invention aims to provide high-corrosion-resistance weather-resistant steel with good corrosion resistance. The chemical components are as follows: c is less than or equal to 0.12%, Si: 2.20-3.00%, Mn is less than or equal to 1.50%, P: 0.060-0.150%, S is less than or equal to 0.015%, Cr: 2.90-3.70%, Ni: 0.10-0.40%, Cu: 0.20-0.60%, Als is more than or equal to 0.010%, and the balance is Fe and inevitable impurities. The weather-resistant steel with high corrosion resistance has the atmospheric corrosion resistance index I of 14.10-15.51 which is obviously higher than 6.0, realizes excellent atmospheric corrosion resistance of the product, can be used in hot and humid areas in a naked mode, is widely applied to the fields of buildings, bridge construction or vehicle manufacturing, and has good application value.)

1.660MPa grade high corrosion resistant weathering steel, its characteristic is: the chemical components by weight percentage are as follows: c is less than or equal to 0.12%, Si: 2.20-3.00%, Mn is less than or equal to 1.50%, P: 0.060-0.150%, S is less than or equal to 0.015%, Cr: 2.90-3.70%, Ni: 0.10-0.40%, Cu: 0.20-0.60%, Als is more than or equal to 0.010%, and the balance is Fe and inevitable impurities.

2. The 660MPa grade high corrosion and weathering steel of claim 1, wherein: the chemical components by weight percentage are as follows: c: 0.06-0.08%, Si: 2.60-2.80%, Mn: 0.85-1.00%, P: 0.080-0.120%, S is less than or equal to 0.007%, Cr: 3.30-3.50%, Ni: 0.20-0.30%, Cu: 0.28-0.38%, Als: 0.015 to 0.050% and the balance of Fe and inevitable impurities.

3. The 660MPa grade high corrosion and weathering steel of claim 1 or 2, characterized by: the atmospheric corrosion resistance index I of the 660MPa grade high-corrosion-resistance weathering steel is 14.10-15.51.

4. The 660MPa grade high corrosion and weather resistant steel according to any one of claims 1 to 3, characterized in that: the yield strength of the 660MPa grade high-corrosion-resistance weathering steel is 660-740 MPa, the tensile strength is 940-1040 MPa, the elongation A is more than or equal to 18%, and the impact value at minus 40 ℃ is more than or equal to 27J.

5. The method for preparing 660MPa grade high corrosion and weather resistant steel according to any one of claims 1 to 4, characterized in that: the method comprises the following steps: molten iron desulfurization → converter smelting → LF → RH → LF → slab continuous casting → hot rolling → laminar cooling → coiling.

6. Use of the 660MPa grade high corrosion and weather resistant steel according to any one of claims 1 to 4, characterized in that: the coating is used in the fields of buildings, bridge construction or vehicle manufacturing, and is exposed in hot and humid areas.

Technical Field

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to 660MPa grade high-corrosion-resistance weathering steel and a preparation method thereof.

Background

The damage of steel corrosion to various fields of national economy and national defense construction is a common and serious problem. According to statistics, in some industrially developed countries, the economic loss caused by corrosion accounts for 2% -4% of the total value of national economic production, wherein atmospheric corrosion is the main form of steel structure corrosion and accounts for about half of the total corrosion loss. Therefore, the method has great significance for the development of weathering steel.

The weathering steel is also named as atmospheric corrosion resistant steel, and is a low alloy steel with good corrosion resistance in the atmosphere. Through a large amount of research at home and abroad, at present, it is generally believed that after long-time exposure to the atmosphere, a layer of compact and good-adhesion oxidation product is generated on the surface of the weathering steel, so that a steel matrix is isolated from external corrosive substances, and the corrosion resistance of the weathering steel is obviously improved.

The domestic weathering steel is mainly used for railway vehicles, containers and the like, and in developed countries such as the United states, Japan and the like, the weathering steel is more widely used in the fields of steel structure buildings and municipal facilities in a naked state. In the united states, the largest use of weathering steel is to construct bridges and expand the use of bare forms, with buildings using bare weathering steel reaching over 500. In japan, from 1965, exterior members such as building roofs, blinds, steel ribs, exterior panel lights, and the like have been exposed to weathering steel. In order to meet the market demand, it is necessary to develop weathering steel having good corrosion resistance.

Disclosure of Invention

The invention aims to solve the technical problem of providing 660MPa grade high-corrosion-resistance weathering steel with good corrosion resistance.

The invention solves the technical problems by adopting the technical scheme that 660MPa grade high-corrosion-resistance weathering steel is provided. The 660MPa grade high-corrosion-resistance weathering steel comprises the following chemical components in percentage by weight: c is less than or equal to 0.12%, Si: 2.20-3.00%, Mn is less than or equal to 1.50%, P: 0.060-0.150%, S is less than or equal to 0.015%, Cr: 2.90-3.70%, Ni: 0.10-0.40%, Cu: 0.20-0.60%, Als is more than or equal to 0.010%, and the balance is Fe and inevitable impurities.

Preferably, the 660MPa grade high-corrosion-resistance weathering steel comprises the following chemical components in percentage by weight: c: 0.06-0.08%, Si: 2.60-2.80%, Mn: 0.85-1.00%, P: 0.080-0.120%, S is less than or equal to 0.007%, Cr: 3.30-3.50%, Ni: 0.20-0.30%, Cu: 0.28-0.38%, Als: 0.015 to 0.050% and the balance of Fe and inevitable impurities.

Further, the atmospheric corrosion resistance index I of the 660MPa grade high-corrosion-resistance weathering steel is 14.10-15.51.

Furthermore, the yield strength of the 660MPa grade high-corrosion-resistance weathering steel is 660-740 MPa, the tensile strength is 940-1040 MPa, the elongation A is more than or equal to 18%, and the impact value at minus 40 ℃ is more than or equal to 27J.

The invention also provides a preparation method of the 660MPa grade high-corrosion-resistance weathering steel, which comprises the following steps:

molten iron desulfurization → converter smelting → LF → RH → LF → slab continuous casting → hot rolling → laminar cooling → coiling.

The invention also provides application of the 660MPa grade high-corrosion-resistance weathering steel in the fields of buildings, bridge construction or vehicle manufacturing, and exposed use in hot and humid areas.

The invention has the beneficial effects that:

the invention provides 660MPa grade high-corrosion-resistance weathering steel with brand new components, which has the yield strength of 660-740 MPa, the tensile strength of 940-1040 MPa, the elongation A of more than or equal to 18 percent and the impact value of more than or equal to 27J at minus 40 ℃. The atmospheric corrosion resistance index I can reach 14.10-15.51, the value is more than twice of 6.0, the relative Q355B corrosion rate is less than or equal to 20%, the atmospheric corrosion resistance is good, the later maintenance cost is low, the service life of the product is long, and the full-period use cost is reduced; meanwhile, the environmental pollution is reduced, and the accident risk of corrosion failure is reduced. The 660MPa grade high-corrosion-resistance weathering steel can be used in hot and humid areas in an exposed manner, can be widely applied to the fields of buildings, bridge construction or vehicle manufacturing, and has wide application prospects.

Detailed Description

The invention provides 660MPa grade high-corrosion-resistance weathering steel, which comprises the following chemical components in percentage by weight: c is less than or equal to 0.12%, Si: 2.20-3.00%, Mn is less than or equal to 1.50%, P: 0.060-0.150%, S is less than or equal to 0.015%, Cr: 2.90-3.70%, Ni: 0.10-0.40%, Cu: 0.20-0.60%, Als is more than or equal to 0.010%, and the balance is Fe and inevitable impurities.

Preferably, the 660MPa grade high-corrosion-resistance weathering steel comprises the following chemical components in percentage by weight: c: 0.06-0.08%, Si: 2.60-2.80%, Mn: 0.85-1.00%, P: 0.080-0.120%, S is less than or equal to 0.007%, Cr: 3.30-3.50%, Ni: 0.20-0.30%, Cu: 0.28-0.38%, Als: 0.015 to 0.050% and the balance of Fe and inevitable impurities.

C is an effective strengthening element in steel, improves the carbon content and is beneficial to improving the strength, but too high carbon content can form more large and thick brittle carbide particles in the steel, is unfavorable for plasticity and toughness, can form a segregation zone in the center of a steel plate, is unfavorable for bending performance and formability, and meanwhile, too high carbon content increases the welding carbon equivalent and is unfavorable for welding processing. Therefore, the invention designs that C is less than or equal to 0.12 percent, and the preferable C is: 0.06-0.08%.

Mn has a strong solid solution strengthening effect, can obviously reduce the phase transition temperature of steel, refines the microstructure of the steel, is an important toughening element, but easily produces casting blank cracks in the continuous casting process when the content of Mn is excessive, and simultaneously can reduce the welding performance of the steel. Therefore, the invention designs that Mn is less than or equal to 1.50 percent, and the preferable Mn: 0.85 to 1.00 percent.

S can form sulfide inclusions to deteriorate the performance of steel, and meanwhile, pitting corrosion expansion is easy to form in the corrosion process, and the corrosion performance is adversely affected. Therefore, the invention designs that S is less than or equal to 0.015 percent, and the preferable S is less than or equal to 0.007 percent.

Al plays a role in deoxidation when added into steel, but the content of Al is too high, and nitrogen oxides are easy to precipitate at austenite grain boundaries to cause casting blank cracks to be generated. Therefore, the invention designs Als more than or equal to 0.010 percent, and the preferred Als: 0.015-0.050%.

In order to improve the atmospheric corrosion resistance of the weathering steel, after the contents of the elements C, Mn, S and Al are determined, the formula I is 26.01 (% Cu) +3.88 (% Ni) +1.20 (% Cr) +1.49 (% Si) +17.28 (% P) -7.29 (% Cu) (% Ni) -9.10 (% Ni) (% P) -33.39 (% Cu) based on the atmospheric corrosion resistance index in appendix D of weather structural steel (GB/T4171-2008)²The contents of Si, P, Cu, Cr and Ni in the steel are determined.

The addition of Cu into steel is favorable for forming a compact amorphous oxide (hydrocarbyl oxide) protective layer with good adhesion on the surface of the steel, and the corrosion resistance is obvious. In addition, Cu forms insoluble sulfides with S, thereby counteracting the deleterious effects of S on steel corrosion resistance. However, when the Cu content is too high, the melting point of Cu is low and is lower than the heating temperature of the slab, and the precipitated Cu is accumulated in the austenite grain boundary in a liquid state, and when the precipitated Cu content reaches a certain level, cracks are easily generated during heating or hot rolling. In addition, according to the calculation formula of the atmospheric corrosion resistance index I, the calculated value of the atmospheric corrosion resistance index I is reduced when the Cu content is too small or too large. Therefore, the present invention designs Cu: 0.20-0.60%, preferably Cu: 0.28 to 0.38 percent.

The Ni is added into the steel, so that the corrosion resistance of the steel is obviously improved, meanwhile, a Ni-containing Cu-rich phase is formed by the Ni and Cu elements and is retained in an external oxidation layer in a solid state, the enrichment amount of Cu in a matrix is reduced, the formation opportunity of a liquid Cu-rich phase is reduced, and the hot brittleness defect is avoided, so that the Ni/Cu content in the steel is generally controlled to be more than or equal to 1/2. However, too high Ni increases the adhesion of scale, hot rolling defects are formed on the surface by pressing into steel, Ni is a precious metal, and too high Ni content significantly increases the cost of steel alloy. Therefore, the present invention designs Ni: 0.10-0.40%, preferably Ni: 0.20 to 0.30 percent.

P can effectively improve the atmospheric corrosion resistance of steel, and when P and Cu are jointly added into the steel, a better composite effect can be displayed, but the plasticity and the low-temperature toughness of the steel are obviously reduced when the content of P is too high. The present invention therefore designs P: 0.060 to 0.150%, preferably P: 0.080-0.120%.

Cr has an obvious effect of improving the passivation capability of steel, can promote the surface of the steel to carry out a compact passivation film or a protective rust layer, and the enrichment of Cr in the rust layer can effectively improve the selective permeability of the rust layer to corrosive media. However, too high Cr content increases the production cost. Therefore, the invention designs Cr: 2.90-3.70%, preferably Cr: 3.30 to 3.50 percent.

Si has high solid solubility in steel, is beneficial to thinning rust layer tissues and reducing the corrosion rate of the whole steel, and the scale removal is difficult during rolling and the welding performance is reduced due to the over-high content of Si. Therefore, the invention designs Si: 2.20-3.00%, preferably Si: 2.60 to 2.80 percent.

Based on the preferable components, the atmospheric corrosion resistance index I of the 660MPa grade high-corrosion-resistance weathering steel can reach 14.10-15.51, the value of the atmospheric corrosion resistance index I is more than twice of 6.0, and the excellent atmospheric corrosion resistance of the product is realized.

The relative Q355B corrosion rate of the 660MPa grade high-corrosion-resistance weathering steel is less than or equal to 20 percent.

The 660MPa grade high-corrosion-resistance weathering steel has the yield strength of 660-740 MPa, the tensile strength of 940-1040 MPa, the elongation A of more than or equal to 18 percent and the impact value of more than or equal to 27J at minus 40 ℃.

The invention also provides a preparation method of the 660MPa grade high-corrosion-resistance weathering steel, which comprises the following steps:

molten iron desulfurization → converter smelting → LF → RH → LF → slab continuous casting → hot rolling → laminar cooling → coiling.

In the preparation method of the 660MPa grade high-corrosion-resistance weathering steel, parameters are controlled in the steps according to the table 1.

TABLE 1 Main technical measures taken and control objectives in the Steps of the preparation method

In the preparation method of the 660MPa grade high-corrosion-resistance weathering steel, in the smelting process, the addition amount of alloy is large, the temperature drop in the process is large, so that the alloy carburization and heating carburization are large, and the ferrochrome is poor in melting effect due to too large temperature drop, so that the RH process insert tube is seriously bonded, so that the production requirement of the steel cannot be met by a common converter smelting → LF → RH → plate blank continuous casting mode.

The smelting process of the 660MPa grade high-corrosion-resistance weathering steel adopts a double LF process, although one LF process is added, the process has more advantages in effective utilization of temperature, component carbon and alloy (alloy loss caused by adhesion of an insert pipe is avoided) and refining sulfur control efficiency, the production risk is reduced to a great extent, and main technical measures and control targets adopted by the processes are shown in the table. The ferrochrome entering the LF procedure for the first time is controlled by reducing the lower limit of the component requirement by 0.15 percent, and because the content of other alloy elements is low and easy to oxidize, the ferrochrome is not prepared when entering the LF for the first time, is primarily prepared after RH decarburization and deoxidation, and is finely adjusted after entering the LF for the second time.

According to the hot rolling and layer cooling process of the 660MPa grade high-corrosion-resistance weathering steel, a casting blank is hot-charged by hot delivery or immediately stacked and slowly cooled and is charged in 24 hours, the discharging temperature is 1240-1280 ℃, the rough rolling full-length descaling is realized, the finish rolling initial temperature is less than or equal to 1020 ℃, the final rolling temperature is 810-850 ℃, cooling water between frames is completely closed, the laminar cooling adopts sparse cooling, and the coiling temperature is 580-620 ℃.

For steel with high alloy content, the casting blank is easy to generate edge crack defects when the stacking time is long and the charging temperature is low, so the casting blank is subjected to hot conveying hot charging or is immediately stacked for slow cooling and is charged in 24 hours.

Iron olivine (Fe) is formed between the iron oxide skin and the matrix during long-term heating of the steel containing higher silicon in the furnace₂SiO₄) Its melting point is 1173 ℃. An effective method for eliminating or reducing the difficulty of descaling silicon-containing steel is to increase the tapping temperature so that the surface temperature of the slab is higher than that of Fe during rough descaling₂SiO₄Does not form FeO/Fe when it is in a liquid state₂SiO₄Easy to remove. Cooling water between the racks is completely closed, so that the rolling speed can be reduced, and the cooling rate is reduced; simultaneous laminar cooling with sparsenessCooling, also to reduce the cooling rate. Because high Cr steel has high hardenability and a large cooling rate, a martensite structure is easy to appear, and therefore, the toughness and the plasticity of a product are adversely affected.

The following examples and comparative examples further illustrate specific embodiments of the present invention.