A kind of thin gauge 30crmo hot-rolled steel plate/band and production method thereof

Abstract

A thin-gauge 30CrMo hot-rolled steel plate / strip and its production method, using elements such as residual Sn and Cu in scrap steel to carry out molten steel smelting, and selectively adding microalloying elements such as Mo and Cr and elements B and N; during the smelting process By controlling the basicity of slag, the type and melting point of inclusions in steel, the content of free oxygen in molten steel, and the content of acid-soluble aluminum Als; In a lower airtight chamber with a non-oxidizing atmosphere, it enters into an online rolling mill for hot rolling in an airtight condition. After rolling, the strip steel is cooled by gas atomization cooling. The thin specification 30CrMo hot-rolled steel plate / strip of the present invention has uniform structure and performance, no shrinkage porosity / shrinkage cavity inside, less decarburization layer, good hardenability, good machinability and machinability; It can be widely used in industries such as machinery manufacturing, petrochemical industry, boiler manufacturing industry, saw blade and die cutting industry.

Description

technical field [0001] The invention belongs to a continuous casting process and products in the metallurgical industry, in particular to a thin-gauge 30CrMo hot-rolled steel sheet / strip and a production method thereof. Background technique [0002] In the traditional steel production process, tin (Sn) and copper (Cu) are typical residual elements or harmful elements in steel. It is very difficult and expensive to fully remove Sn and Cu during the steelmaking process. Once the steel contains Sn , Cu, basically can not be completely eliminated, only by diluting molten steel to reduce the content of Sn, Cu, which all lead to the increase of the smelting cost of iron and steel products. [0003] In recent years, due to the continuous recycling of scrap steel, there are more and more scrap steel resources, and electricity prices have continued to decrease. Sn and Cu in steel are easy-to-segregate elements, which are easily enriched at the grain boundary to cause defects such as...

AI Technical Summary

Problems solved by technology

[0012] (1) Composition segregation and internal porosity: Due to the high alloy content in steel, the casting speed of thick slab continuous casting is low, and the molten steel solidifies slowly, which easily causes serious composition segregation and internal porosity inside the slab, which eventually leads to product quality. uneven performance;

[0013] (2) Surface decarburization: Due to the high carbon content in the steel, a walking heating furnace is used to heat the slab. The heating time is long and the temperature is high, which will lead to serious decarburization on the surface of the slab, which directly affects the surface hardness and durability of the product. abrasiveness and thermal stability;

[0014] (3) Severe cracks on the surface and edge of the slab: the liquidus temperature of 30CrMo is low, and the continuous casting speed of the thick slab is slow, resulting in low temperature of the slab. After entering the high temperature brittle zone, cracks are easy to occur on the surface and edge of the slab , which directly affects product quality

At the same time, the contact of high-temperature strip steel with cooling water will cause many problems: first, water spots (rust spots) will be formed on the surface of the strip steel, which will affect the surface quality; second, the cooling water used for laminar flow cooling or spray cooling It is easy to cause uneven local cooling on the surface of the strip, resulting in uneven microstructure inside the strip, resulting in uneven properties of the strip and affecting product quality; third, uneven local cooling on the surface of the strip will cause deterioration of the shape of the strip , affecting the shape quality

[0017] Indeed, due to its own rapid solidification process characteristics, the products produced by thin strip continuous casting generally have problems such as uneven structure, low elongation, and uneven performance. This is because the austenite grains inside the cast strip have The obvious inhomogeneity will lead to the inhomogeneous structure of the final product obtained after the austenite transformation, which will lead to the instability of the performance of the product, especially the elongation and formability; at the same time, thin strip continuous casting is producing higher carbon When the content of the steel is low, due to the solidification shrinkage, the molten steel has no time to feed, and the problem of internal shrinkage porosity / shrinkage cavity is likely to occur near the central area of ​​the casting belt

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