Stainless steel can be divided into five categories according to its organizational form: ferrite, martensite, austenite, duplex (ferrite + austenite) and precipitation hardening type.
Ferrite wear-resistant plate has a body-centered cubic crystal structure and is low in price because it does not contain precious metals, so it is also called economic stainless steel. Due to its good processing properties, it is widely used in kitchens, household appliances, decoration, and automobile fields. The annual consumption of ferrite wear-resistant plates in the world's stainless steel production is 30-40%.
Its main performance shortcomings are:
The pitting corrosion resistance equivalent of ferrite wear-resistant plate is generally 18-24. Compared with other stainless steels (such as austenitic stainless steel, the pitting corrosion resistance equivalent is greater than 26, and the pitting corrosion resistance equivalent of duplex stainless steel is 30-40). The low pitting corrosion resistance equivalent indicates poor corrosion resistance. The main disadvantages of ferrite wear-resistant plates are room temperature brittleness and high susceptibility to intergranular corrosion caused by various reasons. Among them, the solid solution degree of [C] and [N] in the ferrite wear-resistant plate is low ([N] solid solution degree=927℃, w[N]=230×10-6; [N] solid solution degree=593℃ , w[N]=60×10-6) The formation and precipitation of carbonitrides is very fast, resulting in the rapid formation of chromium-depleted areas at the grain boundaries. Therefore, the manufacturing of ferrite wear-resistant plates should mainly focus on how to reduce the [N] content, improve the purity of the steel and add trace elements niobium and titanium, so that [N] in the steel strongly forms carbonitrides to prevent the formation of grain boundary chromium deficiency. area, refine the grains and prevent intergranular corrosion.
Main ways to improve:
Therefore, to improve the performance of ferrite wear-resistant plates, the [N] content should be controlled as low as possible. Currently, high-purity steel w[N] is less than 230×10-6. Generally, the main technology for producing ultra-low [N] ferrite wear-resistant plates under non-vacuum conditions is to weaken the dissociation of N2 during arc melting, reduce the violent stirring of refining, and reduce the contact time between molten steel and N2 in the air; production under vacuum conditions The main technology for manufacturing ultra-low [N] ferrite wear-resistant plates is to control the increase of [N] during the heating process of the alloy, and then reduce part of the [N] content when removing [C] under vacuum.
