| Low-Carbon steel and Low-Alloy steel are widely used because of their character of good weldability and nice mechanical properties. But the welded joint will have the influence on the security of the whole welded structures. It is necessary to get the joint with good properties among practice. Therefore, it is significant to deeply study microstructure and properties of weld and HAZ (heated affected zone) and to develop the relation between them and welding materials, procedure. Numerical simulation technology is of economic and convenient feature. In this paper, microstructures and properties of low-carbon and low-alloy weld are mainly numerically simulated. Firstly, a 3D numerical model of weld temperature field of low-carbon and low- alloy steel is established and solved by the element difference method, including the factors of thermally physical parameters changing with temperature. Heat transferred among solid is only considered, and one convected among liquid is ignored. Therefore, a mathematical model of welding pool is set up. And then a numerical model is established at the basis of heat transfer equation to make the calculation of the percentage of microstructures and properties of low-carbon and low-alloy steel weld, combining the cooling curve and phase-transformation kinetics. Simultaneously, a mathematical model is established to evaluate the properties of welds. Through quantitative morphology, impact test, tensile test, and hardness test for Q23SD and Q345B steel weld, experimental results indicate that the calculated results have a good coincidence with the measured results. VB6.O is applied to program based on the WINDOWS98. The program can easily calculate the percentage of the final weld microstructures and make the prediction of properties on condition that different welding process and procedure. This program can predict the percentage and properties of weld microstructures adjust the welding procedures on a computer to reach the specific property requirement. |
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