Grain refinement of cast steel

For all kinds of cast alloys, grain refinement is an important measure to improve the metallurgical quality. If the grain size of the cast alloy is small, the area of the grain boundary will increase, and the concentration of various impurities on the grain boundary will decrease accordingly. Therefore, the cast alloy has the following advantages:

(1) The yield strength and tensile strength of the alloy were improved.

(2) Improve the plasticity and toughness of the alloy.

(3) The tendency of hot cracking is small during solidification.

(4) Reduce the scattering of ultrasonic or X-ray, so as to improve the effect of NDT.

(5) For steel castings, it can also reduce the tendency of hot cracking when cutting the pouring and riser.

Of course, the alloy has the advantages of large grain size and good high temperature creep resistance. For example, some blades at the inlet end of high-performance gas turbine, due to their direct contact with high temperature gas, not only need to be made of heat-resistant alloy, but also need to be made of single crystal blades, which is only a special case.

In order to refine the grains of cast alloys, there are many ways, such as increasing the cooling rate in the solidification process, applying vibration or electromagnetic field in the solidification process and adding grain refiners. For casting production, the easiest way is to add grain refiner, which is usually called “inoculation treatment” or “modification treatment” when it is used for cast iron and non-ferrous alloy.

It is an important means to ensure the mechanical properties of cast iron that all kinds of cast iron with graphite in its structure are fine by inoculation. In fact, the fine eutectic is the grain refinement.

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