Caused by improper heating of the defect

(1) coarse grains

Ferrite stainless steel with prime heterogeneous change when heated grain growth tendency. While the grain is too large will cause brittleness and reduce the impact toughness. Therefore, the heating temperature is not too high, not too long residence time at high temperatures.

(2) δ iron ferrite increased

Austenitic duplex steel and martensitic steel is heated to high temperature, there will be too much of δ ferrite, resulting in lower alloy plasticity of the process, which led to the forging crack. 1Cr12Ni2W2MoV steel forging heating temperature is too high, δ phase precipitation quantity caused by forging crack.

(3) low-melting-point compound formation

Containing a high nickel content stainless steel sulfur gas heating, the formation of low melting point NiS or Ni + Ni3S2 crystal, these sulfide eutectic at the grain boundaries, and easy to produce crystals forging steel and nickel-sulfur penetrate between the cracks.

In addition to the above heating defect, the martensitic stainless steel should also slow uniform heating, due to the martensitic steel, high chromium content of chromium improve the steel of the pearlite transformation temperature, slowing the speed of austenite decomposition and lower steel thermal conductivity, resulting in the large temperature stress stress cause blank cracking.



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