A method for producing steel plates for welded structures with excellent z-direction performance by using continuous casting slabs under the condition of small compression ratio

Abstract

The invention discloses a method of using continuous casting slabs to produce steel plates for welded structures with excellent Z-direction performance under the condition of small compression ratio. S, As, Sn and S content at the end point; converter smelting: control oxygen blowing lance position, oxygen pressure, oxygen flow rate, oxygen supply time and fluorite addition amount, 0.05%≤C≤0.07% before tapping, P≤0.003%; Refining treatment time outside the furnace is 45-55 minutes, outbound S ≤ 0.003%, nitrogen increment ≤ 0.002%; vacuum treatment molten steel temperature ≥ 1580 ℃, vacuum degree ≤ 0.13kPa, treatment time 15-25 minutes; the whole process is used to protect pouring, nitrogen Increment ≤ 0.001%, degree of superheat 15-20°C, casting speed 0.75m / min, slab fully closed and slow cooling for more than 72h; heat the slab to 1260-1280°C, stay in the furnace for 420-450min, soaking time 70 ~80min; controlled rolling, cooling, and heat treatment; the cast slab thickness of the present invention is 300mm, 2.30≤compression ratio≤2.75, and the finished steel plate has excellent Z-direction performance and welding performance.

Description

technical field [0001] The invention relates to the technical field of low-alloy high-strength steel manufacturing, in particular to a method for producing steel plates for welded structures with excellent Z-direction performance by using continuous casting slabs under the condition of small compression ratio. Background technique [0002] Low-alloy high-strength structural steel is one of the most important engineering structural materials in my country, and is widely used in building structures, offshore platforms, pressure vessels, boiler manufacturing, water / nuclear power plants, shipbuilding industry, oil and gas pipelines, bridge structures, and heavy machinery manufacturing The construction of various engineering fields of the national economy such as transportation and transportation. With the increasing scale and weight of engineering construction, the requirements for steel materials are getting higher and higher, especially for extra-thick steel plates, which requi...

AI Technical Summary

Problems solved by technology

For a long time, the lack of production technology and technical equipment in our country has caused the mechanical properties of such high-strength thick steel plates in my country to fail to meet the technical requirements of large-scale construction projects, especially the lack of Z-direction performance and welding performance has seriously restricted my country's special The development of thick steel plates, even relying on forging or direct imports from abroad to meet domestic demand

[0003] Domestic extra-thick steel plates are often produced with continuous casting slabs with a thickness of 300mm or more. Due to the large temperature difference between the inside and outside of the slab, the content of carbon, phosphorus, sulfur, manganese and other elements in the center of the slab is likely to be higher than that on the surface of the slab, thus Severe center segregation is caused. During the cooling process of rolled products, hard martensite or bainite structure will be formed in the center of the steel plate, which seriously affects the lamellar tear resistance of the steel plate.

[0004] Before the present invention, Japanese Patent Application No. 6-198394 and No. 6-158222 can produce thick steel plates for building structures with excellent Z-direction performance. The disadvantage is that alloy elements such as Cu, Ni, and Mo are added to the design of the steel plate. , the production cost is high, and the compression ratio is above 3.0, and the maximum thickness of the steel plate is only 75mm

[0005] The Chinese patent No. 2009100481369.2 discloses a special thick steel plate for construction with excellent Z-direction performance and its production method. Lamellar tear performance, the disadvantage is that the steel plate products involved do not have the guarantee of impact toughness, and the compression ratio is ≥ 3.0, and the industrial production technology is not difficult

[0006] The Chinese patent No. 200810141457.9 obtains an ultra-thick steel plate with a thickness of 100-114 mm through quenching + tempering, but the patent contains a lot of precious elements Mo and Cr, which not only has high process costs, but also high alloy costs; the patent No. is The Chinese invention patents of 200810141500.1 and 201010113835.X also obtained ultra-thick steel plates by adding a large amount of precious alloys Mo and Cr, followed by normalizing + tempering or secondary quenching + tempering, but the two patented processes and alloy costs are relatively high. High, not conducive to promotion

[0007] The patent No. 201010159178.2 uses 260mm thick continuous casting slabs to produce Q390E steel plates with a thickness of 100mm and a compression ratio of only 2.6, but the finished steel plates involved cannot guarantee lamellar tear resistance; patent No. 201110302954. The thickness of the Q345EZ35 steel plate produced by the 300mm thick continuous casting slab is 140mm, and the compression ratio is only 2.14. Although the lamellar tear resistance of the finished steel plate involved meets the Z35% requirement, its yield strength and impact energy are at a relatively low level

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