H13 (4Cr5MoSiV1) wear-resistant plate hot work die steel is widely used in hot forging die, die casting die, hot extrusion die and other aspects, is the most widely used hot work die steel. Carbide has an important effect on hardness, hardness, wear resistance and fatigue life of hot work die steel. H13 wear-resistant plate alloy content is high, in the electroslag remelting process will form coarse eutectic carbide and nitride at the solidification end, due to high generation temperature, good thermal stability, in the forging and heat treatment process is difficult to remove, will be retained to the tempered state, significantly reduce the strength of steel, toughness and fatigue properties, how to fine or reduce these coarse carbide, Become the focus of research.
The researchers analyzed the formation of carbide and nitride in electroslag remelting H13 wear-resistant plate from the perspective of thermodynamics, and the conclusions are as follows:
(1) In the process of electroslag remelting production of H13 wear-resistant plate, due to element segregation, the element content in the residual liquid phase gradually increases, TiN is formed when the solid phase ratio reaches 0.82, VC0.88 is formed near the solidification end point, and finally grows into coarse nitides and carbides, which are limited by heat treatment temperature and will be retained in the final product. Adversely affect the properties of steel. The purpose of refining carbide can be achieved by increasing the cooling rate to reduce segregation.
(2) Although the segregation content of V and C elements in the residual liquid phase is already high at the end of solidification, carbides cannot be formed assuming that VC0.88 activity is 1. Due to the high content of Cr, Mo, Fe and other elements in solid solution of carbides, when the activity of carbides is assumed to be 0.3, the theoretical calculation is consistent with the test results, so the activity of carbides in solid solution of various alloying elements cannot be assumed to be 1. While the content of other alloying elements in TiN is small, its activity can be considered as 1;
(3) eutectic carbides formed during solidification, as well as changes in element content and phase transition temperature at different cooling rates, affect the formation temperature of carbides.
