Drawing length is a necessary process in the forging process of large-scale shaft mechanical forgings, and it is also an important process that affects the quality of forging parts. After drawing length, the cross-sectional area of the blank decreases and the length increases, and it also plays a role in breaking coarse crystals, forging loose and holes in the interior, refining the cast structure and so on, so as to obtain homogeneous and dense fine forgings.
When studying the drawing process of flat anvil, people gradually began to realize the importance of the stress and strain state of the inner part of large forgings for the forging inner defects. From the general drawing length of upper and lower flat anvil, to the drawing length of upper and lower V-shaped anvil and the drawing length of upper and lower type anvil, and then to the anvil shape and process conditions after changing the drawing length. WHF forging method, KD forging method, FM forging method, JTS forging method, FML forging method, TER forging method, SUF forging method and new FM forging method are put forward. All these methods have been applied to the production of large mechanical forgings and have achieved good efficiency.
1, WHF forging method: is a wide flat anvil pressing forging method, is developed by Japan steel Research Institute drawing method, was introduced to China in the early 1980s, the forging principle is the use of upper and lower wide flat anvil, and the use of large compression rate, the heart of the forging large deformation is beneficial to remove the internal defects of the ingot is widely used in large hydraulic forging.
2. KD forging method: It was developed by a heavy machinery factory in 1966 on the basis of WHF forging method. Its principle is that steel ingot has enough plasticity under long time high temperature conditions, and can be forged with wide anvil and high compression rate in limited equipment. The use of upper and lower type wide anvil forging is beneficial to increase the metal plasticity on the surface of the forging and increase the three-way compressive stress state of the heart. Then the ingot internal defects are usefully forged.
3. SUF forging method: It is a trowel forging method that reduces the height of the ingot comprehensively during forging by controlling the width ratio of the anvil, and finally forging the cross section into a rectangle. It is a forging method that uses a wide flat anvil to flaten the ingot, and then increases the width of the metal plastic flow range near the axis of the ingot, which is more beneficial to forging the defects of the billet center.
4. New FM forging method: It was put forward by a university professor in the 1990s. According to the relationship between transverse stress and material aspect ratio of the forging heart, the control of material aspect ratio was added on the basis of FM forging method, so as to reduce the transverse tensile stress of the careful part.
After a large number of studies, it is found that the ratio of material to width, the ratio of material to width and the ratio of pressing rate play an important role in the internal void defects of forging mechanical forging. Therefore, it is of great practical significance to further study the size of the ratio of stock to width, the ratio of material to width and the ratio of pressing rate and the matching relationship between them.