Hairpin Bender is main equipment for fin tubing coil fabrication, the funciton of this machine is to make hairpin from 200mm to 4000mm.
We have three different construction hairpin bender machine, First is Automatic hairpin bender( Servo Hairpin Bender ), Second is Semi-automatic hairpin bender(Semi-auto Hairpin Bender) or Hand feeding Hairpin Bender and the last is Manual Hairpin Bender. Three Hairpin Benders has differenct application due to prduction Hairpin Bender Hairpin Bender, Automatic hairpin bender, Hand feeding Hairpin Bender, Manual Hairpin Bender,Servo Hairpin Bender, Semi-auto Hairpin Bender Satis Products Co., Ltd. , http://www.satismachinery.com
Since the gear fracture has a distinct radial pattern, the crack source can be found in the reverse direction at the change in the diameter of the upper edge of the oil hole (2 regions). The crack source is located at the oil hole diameter change (M14 ~ 510), and there is a sharp angle here. This part is prone to stress concentration during quenching treatment, especially for large-size alloy steel parts. The microscopic morphology of the fracture surface of the gear was observed by scanning electron microscope. It was found that: (1) the color of the carburized layer was gray, flat and fine, and there were no defects such as cracks and inclusions, which was the boundary of the junction between the carburized layer and the crack source. (2) The source region of the crack is a sugar-like fracture surface with reflective facets, which is a typical grain-like fracture morphology. An oxide film is present at the edge of the crack source region.
By observing the presence of multiple secondary cracks in the visible section, it is indicated that there is a large internal stress when the gear is cracked. This aspect is caused by the nature of the alloy material. On the other hand, the amount of quenching deformation is large, and the internal stress is not completely eliminated in time when tempering. It can be seen that the hardness of the gear fracture surface is not blocked by the gear oil hole before the carburizing and quenching, and the inner wall of the gear oil hole is carburized and quenched.
Measuring point number abcdefg measuring point position oil hole wall oil hole wall tooth root spline groove core core spoke surface Vickers hardness (HB) Luo gear fracture process analysis gear oil hole upper section processing thread, the upper and lower transition zone has a sharp angle These structures are prone to stress concentration; at the same time, the inner wall of the oil hole is hardened by carburizing during heat treatment of the gear, and after carburizing of 18CrMnTi steel, the austenite stability of each part of the carburized layer is different due to different carbon concentration, such as improper heat treatment process, It is prone to cracks. Through the macroscopic and microscopic morphology analysis of the above-mentioned gear section, it has been confirmed that quenching cracks and a large number of secondary cracks occur at the boundary between the carburized layer and the core at the inner wall of the oil hole after heat treatment of the gear, and they are mostly distributed perpendicular to the inner wall of the oil hole. Structure, materials and heat treatment processes are caused by many reasons.
When the gear transmission is carried, the quenching crack tip of the inner wall of the oil hole is under the complex stress state where the tensile stress and the shear stress work together. At this time, the quenching microcrack first expands, which will mainly depend on the crack size, the bearing capacity in the expansion direction and the stress state. Whether it is conducive to crack propagation. The crack source near the root of the spline groove is in the composite state of tensile stress and shear stress, and the tensile stress is dominant, which is favorable for crack propagation; at the same time, the bearing area in the expansion direction is small; in the stress concentration, the crack tip stress increases significantly along the maximum normal stress. Instantaneous brittle fracture occurs in the direction.
Gear fracture is a low-stress brittle fracture with a flat section. Gear failure fracture is related to improper gear heat treatment process. The gear oil hole is not blocked before carburizing and quenching, and the structure is prone to stress concentration. Failure to completely eliminate residual thermal stress in time. Under the joint action of the two, quenching cracks occur at the interface between the carburized layer and the core at the inner wall of the gear oil hole, resulting in brittle fracture. In the future gear production, before the carburizing and quenching of the gear, the asbestos rope should be used to block the gear oil hole, to avoid the oil hole being carburized and quenched, and to strictly control the heat treatment process.