No. 45 steel is commonly used medium carbon quenched and tempered structural steel. The cold plasticity of No. 45 steel is generally better than A573 grade 70 carbon steel plate. Annealing and normalizing are better than quenching and tempering. No. 45 steel has higher strength and better machinability than Q345 steel. After proper heat treatment, it can obtain certain toughness, plasticity and wear resistance. No. 45 steel A573 grade 70 carbon steel plate is suitable for hydrogen welding and argon arc welding, but not suitable for gas welding. Preheating is required before welding, and stress relief annealing shall be conducted after welding.
The steel such as A573 grade 70 carbon steel plate delivered in the hot-rolled state has a certain degree of corrosion resistance due to the high temperature, so it can be stored in the open air. However, this layer of oxide scale also makes the hot-rolled steel surface rough and the size fluctuates greatly. Therefore, the steel with smooth surface, accurate size and good mechanical properties is required to be produced by using hot-rolled semi-finished products or finished products as raw materials and then cold rolling.
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TMCP process is an important means to improve the comprehensive properties of steel. It can be used to produce ship plate, vessel plate, boiler plate, bridge steel, etc. Compared with the normalized steel of the same strength grade, TMCP can reduce the alloy content of the A573 grade 70 carbon steel plate steel, reduce the carbon equivalent and improve the welding performance. TMCP is more and more widely used in various types of steel rolling industry.
