The surface cleaning of forging blanks, the billet surface quality prepared for heating during precision forging has a great influence on the gear forgings, and it is necessary to remove the defective 淸 from the surface of the bad material, such as leather wallet marks and cracks.
If the forging is required for decarbonization, it should also remove the decarburization layer on the surface of the forging billet. 2, forging blank size to determine the precision forging gears, for the section cone angle in the 28°?62°, and the horizontal direction and height of the maximum profile size of the difference between the small bevel gear, commonly used cylindrical blanks directly in the die in the pre-forging, as shown in the figure. At this time the selected blank diameter should conform to: bevel gear small end of the tooth root circle diameter and tooth top circle diameter.
When the section cone angle is small, it is advisable to take small value. If it is a bevel gear forging with tail column, the selected bad material diameter, also should take into account to the billet put the tail column part of the die off can be easily positioned. Sometimes the upsetting is also used to remove the oxide skin, and the shape of the billet with arc or cone is obtained, so that the billet can be easily placed in the die chamber.
But after the billet is upsetting, the cone of the billet is consistent with the cone angle of the cone gear forgings. For disc bevel gear forgings with larger diameter and smaller height, the billet should be made into precast billet before forging. The design of preform is generally to determine the "equivalent blank" size, which is determined by the gear back cone of any section cone distance, the area of the back cone is equal to the corresponding cone of gear forgings at the back cone area, In this condition the blank size, and on the basis of the appropriate correction (actual forging debugging), to determine the shape and size of the end of the table.