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Except for large and medium-sized parts of open die forging that use steel ingots as blanks, heat forges generally use various metal bars as blanks. Before forging, the bar is generally cut into pieces according to the required size on a special blanking equipment. Common blanking methods are as follows:
1. Sawing
Heat forge sawing and cutting and blanking are often carried out on circular saws, bow saws and high-speed band saws.
(1) The circular saw is driven by the motor to rotate and move the toothed saw disc to cut the bar. The maximum diameter of the saw disc can reach 2m, and the diameter of the forging material that can be sawed is less than 750mm.
(2) The bow saw is driven by the motor to drive the toothed saw blade to move back and forth to cut the bar. The diameter of the bar that can be sawed is less than 100mm. For forging materials with extremely small diameters, they can also be sawed off in bundles and then go through heat forge.
The characteristics of heat forge sawing are that the cut section is flat and the size is accurate; but the productivity is low, there is loss of saw edge, and the loss of saw blade and saw disk is also relatively large. The high-speed band saw is a relatively advanced blanking equipment with high production efficiency and regular blank shapes.
2. Shearing
Shearing for heat forges, which is divided into cold shearing and hot shearing.
Blanking is generally carried out on a shearing machine, which can cut billets with a diameter of less than 200mm.
(1) When a steel billet is cold cut, a great stress will be generated at the sheared part and cracks will appear. Therefore, high carbon steel, alloy steel and steel billets with larger cross-sectional dimensions need to be preheated to 350 to 700℃ before shearing; For low-carbon steel, medium-carbon steel and other steel billets with smaller cross-sectional dimensions, cold shear can be used.
(2) The feature of the shearing machine for heat forge and blanking is that it can be equipped with an automatic feeding and discharging mechanism. The working conditions for the workers are better, the production efficiency is high, the metal is saved, and the utilization rate of the material is improved. However, the shearing end face is not flat and slightly skewed, especially when shearing billets with large diameters under hot conditions. Shearing machines are commonly used in the die forging process of mass production.
Shearing and heat forge blanking can also be carried out on edge-trimming punches, friction press machine and other equipment.
3. The facture blanking in the blanking method of heat forge
(1) Breaking and blanking are carried out on a hydraulic press or a crank press. The pressure is transmitted to the forging material through the punch, so that the material is broken along the pre-cut. Before breaking, the pre-cut is generally made by sawing or gas cutting. The purpose is to cause a large stress concentration at the cut to ensure that when the forging material is broken at a certain position, it does not produce large plastic deformation and affect the quality of the section.
(2) Breaking is suitable for forging materials with higher hardness (high carbon steel and high alloy steel) such as GCr15, GCr15SiMn, GSiMnMo, GSiMnV and other bearing steels, and the heating temperature is 300 to 400℃.
4. The abrasive cutting in the blanking method of heat forge
(1) The abrasive cutting is carried out on the abrasive wheel cutting machine. The abrasive wheel cutting machine is driven by a motor to rotate a thin sheet grinding wheel (generally less than 3mm in thickness) at high speed, and manually or motorized to make it move up and down to cut the billet. The abrasive wheel cutting machine can cut forging materials such as metal blanks with any hardness below 40mm.
(2) The characteristics of abrasive wheel cutting are high productivity and smooth cutting section; however, the loss of thin sheet grinding wheel is large, the working conditions of workers are poor, and good ventilation equipment is required.
5. Flame cutting in the blanking method of heat forge
Flame cutting is also called gas cutting. The principle is to use a gas cutter or an ordinary welding gun to locally heat the steel to the melting temperature with an oxygen gas flow, so as to gradually fuse it. It is mainly used for large section cutting of large billets and forged steel parts (the thickness of the cutting section can reach more than 1500mm), and it can also be used for trimming of large forged steel parts produced in small batches.
6. Anode cutting in the blanking method of heat forge
The principle is to use electric corrosion and electrochemical corrosion to cut metal materials. The size of the forging material to be cut is 30 to 300mm. Anode cutting is characterized by high productivity, less waste, which can cut any hardness of metal materials, and has a smooth section.
