WO2019076048A1

WO2019076048A1 - Weatherable steel plate and manufacturing method therefor

Info

Publication number: WO2019076048A1
Application number: PCT/CN2018/088135
Authority: WO
Inventors: 邓伟; 崔强; 李恒坤
Original assignee: 南京钢铁股份有限公司
Priority date: 2017-10-19
Filing date: 2018-05-24
Publication date: 2019-04-25
Also published as: CN107841689B; CN107841689A

Abstract

A weatherable steel plate and a manufacturing method therefor. The weatherable steel plate comprises the following components by mass percentage: 0.04-0.10% of C, 0.18‑0.35% of Si, 1.00‑1.60% of Mn, 0.008‑0.015% of P, 0.25‑0.45% of Cu, 0.40‑0.60% of Cr, 0.30‑0.50% of Ni, 0.02‑0.05% of Alt, 0.01‑0.05% of Nb, with the balance being iron and unavoidable impurities. The steel sheet can obtain excellent welding performance, and has ultra-high strength, high toughness and high weather resistance at a low P content by means of a reasonable ingredient proportion.

Description

Weathering steel plate and manufacturing method thereof

Technical field

The present invention relates to an alloy steel sheet, and more particularly to a weather resistant steel sheet for a single rail crucible and a method of manufacturing the same.

Background technique

The monorail is a type of railway that features only one track. Similar to urban rail transit systems, monorails are mainly used in urban densely populated areas to carry passengers. The monorail is usually elevated, with the advantages of low cost, low pollution and short construction period. The monorail railway occupies less land and can effectively use the central isolation belt, which is an effective way to improve urban traffic.

However, the weather-resistant steel sheets used for manufacturing single-track rafts mostly improve the corrosion resistance by increasing the P content in the steel sheets, ignoring the toughness and weldability of the steel sheets. Moreover, the content of Cu, Cr, and Ni is relatively small, the weather resistance is insufficient, and the manufacturing process is relatively complicated, and performance and production cost cannot be balanced.

Summary of the invention

OBJECT OF THE INVENTION In order to solve the deficiencies of the prior art, the present invention provides a weather-resistant steel sheet which provides a steel sheet having a low alloy cost, excellent weldability, and ultra-high strength, high toughness and weather resistance for a single rail.

Another object of the present invention is to provide a method for producing a weather-resistant steel sheet which can produce a weather-resistant steel sheet having both cost and performance described above.

Technical Solution: A weather resistant steel sheet according to the present invention contains C: 0.04 - 0.10%, Si: 0.18 - 0.35%, Mn: 1.00 - 1.60%, P: 0.008 - 0.015%, Cu: 0.25 by mass%. -0.45%, Cr: 0.40-0.60%, Ni: 0.30-0.50%, Alt: 0.02-0.05%, Nb: 0.01-0.05%, the balance being iron and unavoidable impurities.

The reasons for limiting the components of the weathering steel sheet according to the present invention are as follows:

C: It adopts low-carbon component design. The high carbon content is very unfavorable to the impact toughness of steel, especially the impact energy of the upper platform, and it obviously impairs the welding performance. At the same time, considering the difficulty of production control, the carbon content can not be too low, so The content is limited to 0.04-0.10%.

Si: Silicon is a deoxidizing element in the steel making process, and an appropriate amount of silicon can inhibit the segregation of manganese and phosphorus, and can increase the strength of the steel by solid solution strengthening, but the silicon content is too high and deteriorates the welding performance and low temperature of the steel. Resilience, therefore limiting its content from 0.18 to 0.35%.

Mn: Manganese is the necessary element for deoxidation in the steel making process. It also increases the strength of the steel by solid solution strengthening. In order to achieve a sufficiently high tensile strength, the manganese content cannot be too low, but the excessive manganese content can also deteriorate the steel. Welding performance and low temperature toughness, so the content is limited to 1.00-1.60%.

P: Phosphorus is a beneficial element for weather resistance. If the phosphorus content is too low, the weather resistance is difficult to guarantee, but the phosphorus content is too high, which will deteriorate the low temperature toughness of the base metal and the welded joint. Especially in the welding process, the phosphorus in the base metal will be Excessive into the weld, forming a eutectic, resulting in a decrease in the impact energy of the welded joint, so the content is limited to 0.008-0.015%.

Cu: Copper can promote the formation of a stable and dense rust layer on the surface of the steel sheet, and can also improve the weather resistance of the steel sheet. However, if the copper content is too high, it will cause hot brittleness during the processing of the steel sheet and deteriorate the surface properties of the steel sheet, so the content is limited to 0.25-0.45%. .

Cr: Chromium can also effectively improve the weather resistance of steel, and it can also produce solid solution strengthening. However, if the chromium is too high, the toughness and weldability of the steel will be lowered, so the content is limited to 0.40-0.60%.

Ni: Nickel is also one of the elements for improving the weather resistance of steel, and it can promote the formation of a stable rust layer, and can also improve the welding performance, but excessive addition of nickel element can significantly increase the cost, and therefore, the content thereof is limited to 0.30 to 0.50%.

Al: aluminum is a deoxidizing element in the steel making process, which can also reduce the amount of solid solution N atoms, thereby improving the toughness and time effect resistance, and the formed AlN can also refine the grains, thereby further reducing the ductile-brittle transition temperature, however, Excessive addition forms large-sized Al ₂ O ₃ and AlN and impairs toughness, so the control Alt is 0.02-0.05%.

Nb: niobium can increase the strength of steel. At the same time, niobium can also increase the austenite recrystallization temperature, and can achieve non-recrystallization zone rolling at higher temperatures, but the strengthening effect on steel after the increase of niobium content is limited. Therefore, its content is limited to 0.01 to 0.05%.

Wherein, the composition of the steel plate satisfies Cu+Cr+Ni≤1.35% by mass%; Cu, Cr, and Ni are all key elements affecting the weather resistance of the steel sheet, and the more general content, the more excellent the weather resistance, but Cu, Cr and Ni are also the forming elements of the MA island component, and the MA island is easily formed during the cooling process of the weld heat affected zone, resulting in deterioration of toughness. Therefore, under the premise of ensuring that the weather resistance is not lowered, Cu + Cr + Ni ≤ 1.35%.

The carbon equivalent CEV of the steel plate is ≤0.46%; and the carbon content of the steel plate is combined with 0.04-0.10%, so that the steel plate is in the easy-welding region, ensuring good weldability, and the weldability of the carbon equivalent is higher than 0.46%.

The welding cold crack sensitivity index of the steel plate is Pcm≤0.21%, so that the crack is not easy to occur during welding, and the preheating can be avoided. The heat treatment can be omitted after welding. When the Pcm is higher than 0.21%, the welding is prone to cracking, and heat treatment is needed after welding. Stress and weldability deteriorate.

The weather resistance index of the steel plate is ≥ 6.5, which can ensure good weather resistance and can be protected from anti-corrosion coating.

Further, the carbon equivalent CEV of the steel sheet is 0.36-0.46%, the weld cold crack sensitivity index Pcm of the steel sheet is 0.15-0.21%, and the weather resistance index I of the steel sheet is 6.5-7.0. When the carbon equivalent is less than 0.36%, the yield strength and weather resistance index of the steel sheet are difficult to ensure. Similarly, when the Pcm is less than 0.15%, the yield strength and weather resistance index of the steel sheet are difficult to ensure, and when I is greater than 7.0, it is necessary to add. A large amount of alloying elements, the cost is inevitably increased, and the weldability is also deteriorated.

The present invention also provides a method of manufacturing the above weather resistant steel sheet as follows:

The process includes smelting, refining, continuous casting, heating and rolling; wherein the heating process is to heat the slab to a complete austenitizing temperature; the rolling process adopts an austenite recrystallization zone and an austenite non-recrystallization zone. a stage rolling process; wherein the austenite recrystallization zone is rolled into a rough rolling stage, the rough rolling refines austenite grains by repeated austenite recrystallization, and the austenite non-recrystallization zone is rolled into a finishing stage , obtaining a hardened austenite structure after finish rolling;

The rolling temperature in the finishing rolling stage is 850-970 ° C, the finishing rolling temperature is 780-860 ° C, the residence time after finishing rolling is 10-30 seconds, and then cooled to 450-600 ° C by ultra-rapid cooling technology, followed by air cooling to room temperature; After deformation, the austenite stays for 10-30 s, that is, relaxes for a period of time and then accelerates the cooling. The dislocation density is reduced during the relaxation process, the dislocation structure changes and the volume fraction of the precipitated phase increase, and the medium temperature transition is refined. In addition, the precipitation of the relaxation process promotes the nucleation, and the nano-sized precipitated particles are not only harmless to the performance of the steel, but also exert a precipitation strengthening effect.

[Advantageous Effects] The weather-resistant steel sheet according to the present invention obtains a steel sheet excellent in weldability and high in super high strength, high toughness and high weather resistance at a low P content by adopting a reasonable alloy distribution ratio. The mechanical properties are: yield strength Rp0.2≥485MPa, tensile strength Rm≥585MPa, elongation A≥20%, yield ratio YR≤0.85, -60°C impact energy KV2≥200J, ductile-brittle transition temperature is lower than- 80 ° C. The welding performance characteristics are: the steel plate with a thickness of 60mm or less does not need to be preheated before welding, no heat treatment after welding, good weldability, high welding efficiency, and can well meet the application of single track boring. The method for manufacturing the weathering steel plate adopts a two-stage rolling process of austenite recrystallization zone and austenite non-recrystallization zone, repeatedly refining the austenite grain structure, improving the strength of the steel plate, and eliminating quenching during the production process. Tempering reduces production costs and shortens production cycles.

DRAWINGS

Figure 1 is a metallographic photograph of the microstructure of a weather resistant steel sheet.

Detailed ways

The present invention will be further described below in conjunction with the embodiments.

According to the method for producing a weather-resistant steel sheet according to the present invention, the weather-resistant steel sheet according to the present invention is obtained through processes such as smelting, refining, continuous casting, heating, and rolling; wherein the slab is heated to a complete austenitizing temperature during the heating process The rolling process adopts a two-stage rolling process of austenite recrystallization zone and austenite non-recrystallization zone, and can also be two-stage rolling of rough rolling and finishing rolling, and the rolling rolling temperature of the finishing rolling stage is 850-970 ° C. Finish rolling temperature 780-860 ° C, after rolling for 10-30 seconds, and then cooled to 450-600 ° C by ultra-rapid cooling technology, then air cooled to room temperature, as shown in Figure 1, metallographic photograph shows the microstructure of the weathering steel The structure is fine ferrite + bainite + pearlite grain structure.

Among them, the calculation formula between the value of carbon equivalent and each chemical component is:

CEV (%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15.

The formula for calculating the cold crack sensitivity index and the chemical composition of the weld is:

Pcm (%) = C + Si / 30 + (Mn + Cu + Cr) / 20 + Ni / 60 + Mo / 15 + V / 10 + 5B.

The formula for calculating the weathering index and each chemical composition is:

I=26.01*Cu+3.88*Ni+1.2*Cr+1.49*Si+17.28*P-7.29*

Cu*Ni-9.1*Ni*P-33.39*Cu*Cu.

Six sets of weathering steel sheets were produced by the above manufacturing method, and the components of the six sets of weathering steel sheets were measured by mass% as follows:

S1: C: 0.04%, Si: 0.35%, Mn: 1.20%, P: 0.012%, Cu: 0.30%, Cr: 0.40%, Ni: 0.30%, Alt: 0.02%, Nb: 0.035%, CEV: 0.36 %, Pcm: 0.15%, I: 6.50, Cu + Cr + Ni = 1.0%.

S2: C: 0.06%, Si: 0.18%, Mn: 1.40%, P: 0.015%, Cu: 0.25%, Cr: 0.60%, Ni: 0.45%, Alt: 0.04%, Nb: 0.015%, CEV: 0.46 %, Pcm: 0.19%, I: 6.50, Cu + Cr + Ni = 1.3%.

S3: C: 0.1%, Si: 0.35%, Mn: 1.10%, P: 0.014%, Cu: 0.25%, Cr: 0.55%, Ni: 0.45%, Alt: 0.04%, Nb: 0.01%, CEV: 0.44 %, Pcm: 0.21%, I: 6.70, Cu + Cr + Ni = 1.25%.

S4: C: 0.04%, Si: 0.35%, Mn: 1.00%, P: 0.008%, Cu: 0.45%, Cr: 0.6%, Ni: 0.30%, Alt: 0.02%, Nb: 0.01%, CEV: 0.38 %, Pcm: 0.16%, I: 6.50, Cu + Cr + Ni = 1.3%.

S5: C: 0.08%, Si: 0.34%, Mn: 1.00%, P: 0.015%, Cu: 0.30%, Cr: 0.55%, Ni: 0.5%, Alt: 0.05%, Nb: 0.05%, CEV: 0.41 %, Pcm: 0.19%, I: 7.00, Cu + Cr + Ni = 1.35%.

S6: C: 0.04%, Si: 0.35%, Mn: 1.60%, P: 0.08%, Cu: 0.30%, Cr: 0.5%, Ni: 0.4%, Alt: 0.03%, Nb: 0.02%, CEV: 0.45 %, Pcm: 0.18%, I: 6.70, Cu + Cr + Ni = 1.2%.

For the above-mentioned 6-component steel plates, two sets of different thickness samples were rolled in each group, and each component was rolled out with a 60 mm-thickness sample. The manufacturing process parameters are shown in Table 1:

Table 1 Process parameters for the production of weather-resistant steel sheets for each single track

The mechanical properties of 6 sets of steel plates were tested. The experimental results are shown in Table 2:

Table 2 Mechanical properties of weather-resistant steel sheets for each single track

The welding performance test was carried out on 6 samples of 60 mm thick. The results are shown in Table 3:

Table 3 Welding performance of weather-resistant steel sheets for each single track

The above experimental data fully demonstrates that the weather resistant steel sheet of the present invention has good weather resistance and weldability.

Claims

A weather-resistant steel sheet characterized by containing C: 0.04 - 0.10%, Si: 0.18 - 0.35%, Mn: 1.00 - 1.60%, P: 0.008 - 0.015%, Cu: 0.25 by mass%. -0.45%, Cr: 0.40-0.60%, Ni: 0.30-0.50%, Alt: 0.02-0.05%, Nb: 0.01-0.05%, the balance being iron and unavoidable impurities.
The weather-resistant steel sheet according to claim 1, wherein the composition of the steel sheet further satisfies Cu + Cr + Ni ≤ 1.35% by mass%.
The weather-resistant steel sheet according to claim 1, wherein the steel sheet has a carbon equivalent CEV ≤ 0.46%, a weld cold crack sensitivity index Pcm ≤ 0.21%, and a weather resistance index I ≥ 6.5.
The weather-resistant steel sheet according to claim 3, wherein the steel sheet has a carbon equivalent CEV of 0.36 to 0.46%, a weld cold crack sensitivity index Pcm of 0.15 to 0.21%, and a weather resistance index of 6.5 to 7.0.
The method for producing a weather-resistant steel sheet according to any one of claims 1 to 4, wherein the step comprises smelting, refining, continuous casting, heating, and rolling; wherein the heating step is heating the slab to complete austenite The temperature is controlled; the rolling process adopts a two-stage rolling process of austenite recrystallization zone and austenite non-recrystallization zone.
The method for producing a weather-resistant steel sheet according to claim 5, wherein in the rolling step, the rolling temperature of the austenite non-recrystallization zone is 850-970 ° C in the rolling stage, and the finishing temperature is 780-860 ° C. After the system is kept for 10-30 seconds, it is cooled to 450-600 ° C by ultra-rapid cooling technology, and then air cooled to room temperature.