What are the blanking methods before forging?

Forging before cutting several methods. Forgings before heating and forging, raw materials should be cut into a reasonable size and length, called blanking. Usually free forging method is used to open the billet, and then the raw materials (steel ingot, billet) two forging cut, and according to a certain size of the billet will be separated for heating. The usual blanking methods are shear, cold folding, sawing, turning, grinding wheel cutting, cutting and other blanking methods have their own characteristics, according to the nature of the material, size, batch and the requirements of blanking quality. Their blank quality, material utilization rate processing efficiency is different. So according to the above conditions to choose forging products suitable blanking method.

There are mainly sawing off the material method, shear off the material method, grinding wheel slice cutting method, electric spark cutting, broken hair (also called cold folding). Other blanking methods include friction sawing, electromechanical sawing, anodic mechanical cutting, electric spark cutting, precision blanking methods, etc.

Sawing cutting method

The raw materials should be blanked before production and processing. Sawing can cut off the billet with large cross section, although the productivity is low, the saw mouth loss is large, only because of the cutting precision, smooth incision, especially in the fine forging process, is a main blanking method. Commonly used cutting saws are disc, band saw and bow saw.

Shear blanking method

Shear blanking is characterized by high production efficiency, simple operation, fracture without metal consumption, simple tools, low mold costs. But the face quality punch and cutting method of blanking poor. Suitable for batch mass production, is widely used. The shearing process is through the action of the upper and lower blades to the billet with a certain pressure (F), bending and tensile deformation in the billet production, when the stress exceeds the shear strength of the forging raw material fracture.

Grinding wheel cutting method

Suitable for cutting small section bar material, pipe material of special section material, as well as other material cutting method difficult to cut metal, such as high temperature alloy GH33, GH37, etc.. The advantages are simple equipment, convenient operation, accurate feeding length, good end quality, productivity is higher than the saw blade small material and lower than the shear cold folding feeding, load grinding wheel consumption, and fragile, large noise.

Spark cutting

Its working principle is: dc motor through resistance R and capacitance C, so that the blank is connected with the positive pole saw blade connected with the negative pole, cutting in the electrolyte, the pulse current intensity of the production of electric spark is very large, up to hundreds or thousands of amperes; The pulse power reaches tens of thousands of watts. The contact area at the cutting point is small, so the current density may be as high as hundreds of thousands of A/mm2. Therefore, the local temperature on the blank is very high, about 10,000 °C, which promotes metal melting to achieve the purpose of blanking.

Broken hair (also called cold folding)

The original work is to break a small gap, under the pressure F, the stress concentration in the gap to break the billet. The reason is that when the average stress in the blank reaches the yield limit, the local stress in the gap has already exceeded the strength limit, so the blank has broken too late to shape the deformation.