Support rolls refer to the rolls that can increase the rigidity of the work rolls and directly or indirectly bear the rolling load, which is an important part to prevent the work rolls from flexural deformation and affect the quality of plate shape. Support roll body to withstand a lot of bending stress and friction, roll surface due to long time wear, impact, contact stress and heat and cold caused by indentation, cracks, spalling. A good support roll should have the following properties:
1)Sufficient strength and toughness, roll body, roll neck to withstand the work stress without transverse fracture.
2) Wear resistance, refers to the support roll roll body working parts in rolling to resist weight loss and size reduction ability. Support rollers in the hot state of wear resistance and cold state of wear resistance is not necessarily the same!
3) Spalling resistance, refers to the support roll in the contact stress for a long time without producing the roll body falling block phenomenon.
4) Resistance to thermal cracking, the rolling material and cooling water of the radical cold and heat on the support rolls, does not produce reticulate cracking
Traditional support roll material used more is 9Cr2Mo, carbon content of 0.9% or so, chromium content of 2%, and a small amount of molybdenum, the material is a typical cold roll material, after heating and intense cooling can obtain a high surface hardness and a certain degree of wear resistance. Previously, the production of forged steel rolls due to the lack of special support roll material, so more often used the material after quenching and tempering to medium-low hardness as a support roll use. With the improvement of mill design requirements and changes in rolling conditions, often require the work roll requires wear resistance, anti-accident, anti-roll stamping, high uniformity, the work of the rollers on one side of the depth of 25mm or more, 9Cr2Mo due to high carbon content, there are more carbides in the substrate, these carbides, if not properly handled, the distribution of the state of the unsatisfactory, will reduce the substrate's fatigue strength; in addition to the material in the Cr / C than Decide the carbide of the material, the hardness is low (about 900HV), the roll wear resistance contribution is not enough.
Now 70Cr3Mo series become the first choice of support roll material, some high-speed heavy-duty mill support roll material using 50Cr4MoV and 45Cr5MoV series material.
