When inner hexagonal cylindrical head bolts are manufactured by cold heading process, the original structure of steel will directly affect the forming ability of cold heading process. The plastic deformation of local area in cold heading process can reach 60%-80%. Therefore, steel must have good plasticity. When the chemical composition of steel is constant, metallographic structure is the key factor to determine the plasticity. It is generally considered that large flake pearlite is not conducive to cold upsetting, while fine spherical pearlite can significantly improve the plastic deformation ability of steel. In order to obtain uniform and fine spheroidized pearlite, spheroidizing (softening) annealing was carried out before cold heading for medium carbon steel and medium carbon alloy steel with more high strength bolts, so as to better meet the actual production needs. For softening annealing of medium carbon steel wire rod, the heating temperature mostly chooses to keep warm at the critical point of the steel. The heating temperature can not be too high. Otherwise, three cementite precipitates along the grain boundary, resulting in cold heading cracking. For medium carbon alloy steel wire rod, isothermal spheroidizing annealing is adopted. After heating with AC1+ (20-30%), the furnace is cooled to a little lower than Ar1 and the temperature is about 700 degrees Celsius. After a period of time, the furnace is cooled to about 500 degrees Celsius and the air is cooled out. The metallographic structure of steel changes from coarse to fine, from flake to spherical, and the cracking rate of cold heading will be greatly reduced. The softening annealing temperature of 35 45 ML35 SWRCH35K steel is 715-735 degrees Celsius, while the spheroidizing annealing temperature of SCM435 Cr SCR435 steel is 740-770 degrees Celsius and the isothermal temperature is 680-700 degrees Celsius.

Metric Bolts ASTM

Metric Bolts ASTM

Metric Bolts ASTM DIN933 DIN934 ASTM A193M Standard: DIN,UNC,BSW,UNF,ASTM, DIN,UNC,BSW,UNF Product name: Metric Bolts ASTM A193M ASTM A325M Grade: 4,8/ 8.8/ 10.9/ 12.9 Ect Color: Oxidation blackening,Zinc plating, Surface treatment: HDG, PTFE coated, plain, black, galvanized, yellow zinc plated Packing: 25kg carton then pallet or according to the customer’s need. Application: Machinery industry Length: 15-200mm,customized […]


Galvanized Heavy Hex Bolt

Galvanized Heavy Hex Bolt A325M

Hexagonal Cylindrical Head Bolts, Galvanized Heavy Hex Bolt A325M detail information: Material: Stainless Steel: SS201, SS303, SS304, SS316, SS410, SS420 Carbon Steel: 4.8, 6.8, 8.8, 10.9, 12.9 Titanium: GR1-GR5, Aluminum, Brass,etc. Size: M1.6-M39 Length: Up to 300mm Head Type: Flat, JIS pan, Oval, Round, Binding, I.HD, Brazier, PF. HD, Button, Fillister, Ansi.Pan, Pan washer,Indented Hex etc. Standard: ISO,GB, DIN, […]