Smelting method for improving cutting performance of round steel for machinery

Abstract

The invention relates to a low-cost smelting method of round steel, in particular to a low-cost smelting method for improving cutting performance of round steel for machinery. The method comprises a converter smelting procedure, an LF furnace external refining procedure and a bloom continuous casting procedure; the converter lime and limestone consumption is properly reduced to reasonably reduce the basicity of furnace slag to increase the converter terminal sulfur content; the converter tapping carbon content is properly increased; the reasonable tapping temperature is selected; and the furnace external refining process is optimized. The round steel for machinery, produced by the method, is simple in operation, low in cost, high in purity, excellent in cutting performance and excellent in casting property. Compared with a traditional process, the smelting method guarantees the sulfur content in a finished product, satisfies the cutting requirement of customers, reduces the production cost, and solves such technical difficulties as weak continuous casting performance, easy generation of nodules, low purity and unstable quality in traditionally produced easy-cut round steel for machinery.

Description

technical field [0001] The invention relates to a production method of steel, in particular to a low-cost smelting method for improving the cutting performance of round steel for machinery. Background technique [0002] Mechanical steel is one of the most widely used steel series in the steel consumption market, and is widely used in construction machinery, automobiles and home appliances and other industries. Steel for construction machinery refers to the structural steel used to manufacture mechanical parts that bear load or transmit work and force, also known as machine structural steel. The requirements for this type of steel are high strength, proper toughness and good manufacturing processability, such as forgeability and machinability. Such steels are generally used after proper heat treatment. Steel for machinery manufacturing can be divided into quenched and tempered steel, case hardened steel (including carburizing steel and nitrided steel), spring steel and roll...

AI Technical Summary

Problems solved by technology

[0008] In the process of steelmaking, the content of phosphorus, oxygen and other elements in molten steel must be strictly controlled. Phosphorus is completely dissolved in ferrite in steel, which can improve the strength and hardness of ferrite, but it makes The plasticity and impact toughness of steel decrease sharply at low temperature, making the steel brittle. This phenomenon is called "cold brittleness". Adverse effects; if the oxygen content in molten steel is too high, defects such as subcutaneous bubbles and looseness will occur, and a large number of inclusions will be generated and remain in molten steel, which will greatly reduce the mechanical properties of steel such as plasticity and impact toughness

Therefore, the slag must ensure a certain high alkalinity during smelting and refining. Blindly lowering the alkalinity of the slag will cause difficulty in dephosphorization of molten steel, high oxygen content, high content of inclusions, and defects such as pores on the surface are prone to occur, resulting in rolling. The obvious decline in material quality cannot meet the usability requirements of users

[0009] At present, most domestic related production enterprises use high-basicity slag desulfurization. Taking 40Cr as an example, the basicity of refining slag is controlled at about 4.2%. The sulfur ions formed can easily form stable sulfides with cations in the steel such as calcium ions, which are absorbed by the slag and removed. Therefore, the sulfur content in molten steel will be relatively low (generally, the sulfur content is only 0.001 %~0.005%), so in order to meet the requirements of users, the enterprise adopts the process of feeding sulfur iron wire to increase sulfur during subsequent soft blowing, which will cause difficulties in continuous casting. Increased production costs, but also seriously affected product quality, while reducing production efficiency

How to choose the production process can not only meet the machinability requirements of users, but also reduce production costs. These technical problems have greatly troubled the manufacturers of mechanical steel

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