Service HotlineWhen the countersunk head screws and hexagon socket head bolts are produced by the cold heading process, the original structure of the steel will directly affect the forming ability of the cold heading process. In the process of cold heading, the plastic deformation of the local area can reach 60%-80%, so the steel must have good plasticity. When the chemical composition of the steel is constant, the metallographic structure is the key factor to determine the plasticity. It is generally believed that the coarse flaky pearlite is not conducive to cold heading forming, while the fine spherical pearlite can significantly improve the plastic deformation ability of the steel. For medium carbon steel and medium carbon alloy steel with a large amount of high-strength bolts, spheroidizing (softening) annealing is performed before cold heading, so as to obtain uniform and fine spheroidized pearlite to better meet the actual production needs. For the softening annealing of medium carbon steel wire rods, the heating temperature should be kept above and below the critical point of the steel, and the heating temperature should not be too high, otherwise tertiary cementite will precipitate along the grain boundary, resulting in cold heading cracking. The wire rod of medium carbon alloy steel is annealed by isothermal spheroidization. After heating at AC1+ (20-30%), the furnace is cooled to slightly lower than Ar1, the temperature is about 700 degrees Celsius for an isothermal period, and then the furnace is cooled to about 500 degrees Celsius and air-cooled. The metallographic structure of the steel changes from coarse to fine, from flake to spherical, and the cracking rate of cold heading will be greatly reduced. The general area of softening annealing temperature for 35\45\ML35\SWRCH35K steel is 715-735 degrees Celsius; while the general heating temperature for spheroidizing annealing of SCM435\40Cr\SCR435 steel is 740-770 degrees Celsius, and the isothermal temperature is 680-700 degrees Celsius.
1. Material strain hardening When the material is cyclically loaded, the phenomenon of cyclic strain hardening or cyclic strain softening will occur, that is, under the condition of constant cyclic strain, the stress amplitude will increase or decrease with the increase of the number of cycles. . After several cycles, the stress amplitude enters a cyclic steady state. The low-cycle fatigue of the lock nut is carried out under the condition that the strain is constant, and the strain hardening or softening of the threaded piece will affect the size of its maximum unscrewing torque. The alloy steel used to make the lock nut is a cyclic strain hardening material, and the hardening of the material will increase the elastic restoring force FN of the threaded sheet and increase the unscrewing torque.
Moisture-proof measures Iron screws are easy to rust in a humid environment. In order to prevent the screws from rusting, the screws need to be moisture-proof and moisture-proof. The moisture-proof and moisture-proof methods of screws are as follows: (1) Vibration machinery, try to use solvent-free paint. (2) It is best to use impregnating paints that do not contain oxidative components, such as epoxy-urethane (Epoxy-urethane)-based or unmodified epoxy-based (Epoxy-)-based impregnating paints. (3) When using melamine alkyd impregnating paint, the curing temperature and curing time should be adjusted. The curing temperature should be slightly higher than 130 °C (such as 135 °C) and the curing time should be longer than 180min, and the process must be strictly implemented, especially In the hot and humid season, the drying (curing) time of the paint specified in the paint factory's samples is not necessarily sufficient from the perspective of rust prevention, and the motor has a specific inner shape. (4), use paint without volatile acid. (5) Choose paint with good hydrolysis resistance.
In the field of mechanical design, there are a large number of connector connection structures that need to be fastened and positioned. As shown in Figure 1, the more common positioning and fastening connection methods at present are that pins 5 and fasteners are used for positioning and fastening, respectively. That is, cylindrical pins or taper pins are used for positioning, and fasteners such as screws or double-ended studs are used for fastening.
During the tightening process of the screw, do not use excessive force, otherwise the product will be damaged. The traditional bolt locking adopts manual operation, which is inefficient and insufficient force. In the existing screw locking device, before locking the screw, the locking force of the screw is tested, but the test equipment is set separately, resulting in a complicated structure. In addition, in the existing screw locking device, when the screw is locked, the position of the screw hole is not corrected, so that the screw often causes damage to the product during the tightening process.
We have many years of experience in the production and sales of screws, nuts, flat washers, etc. The main products are: blackened bolts, connecting rod top posts, 304 cylindrical pins, round head Phillips screws and other products, we can provide you with fastening suitable for you piece solution.
