Molybdenum News Center

TZM Alloy Plate Cogging

After sintering molybdenum and TZM alloy due to high melting point, large deformation resistance, small plastic range, so the heating temperature can’t be low, otherwise it can not employ rolling process. When molybdenum plate heating temperature is higher than 1100℃, there has little plasticity, and when the temperature is higher than 1250 ℃ the ductility has significantly improve. Reasonable cogging temperature of molybdenum plate not only can reduce the deformation resistance during cogging process, but also ensure fracture does not occur in a large cogging pressure.

TZM alloy cogging temperature can not too high. High cogging temperature not only makes grains coarse, but also reduces structure properties of the alloy. However, the cogging temperature can’t too low. Low cogging temperature is easy to make alloy blank cracking. To select the appropriate cogging temperature should not only consider the past experience, but also should consider powder metallurgy technology. TZM alloy plate has higher deformation resistance and plastic is poor, so the cogging temperature is generally about 1400 ℃.

The rolling reduction of cogging refers to the total processing rate. The total processing rate refers to the deformation degree, and it can decide the structure and properties of materials. TZM alloy and pure molybdenum has same cogging rolling reduction, which is about 25%~ 35%. Large amount of deformation not only make internal deformation of alloy uniform, but also in the subsequent processing there is delamination and breakage and other defects occur. In addition, a large amount of deformation can crush closed pores and voids.

Molybdenum is easily oxidized in air, resulting in pits showing in the surface during rolling process, affecting the surface quality and subsequent rolling process of alloy. In addition, this will reduce alloy’s friction, thereby undermining the biting conditions and rolling conditions stabilize, showing slip phenomenon. Therefore, before rolling, the alloy plate should fall twice on the tool bench, so that most of the scale cinders were shattered, and then rapidly to roll process. During hearing process, TZM alloy plate blank should protect by hydrogen to prevent molybdenum oxidation.

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