Hot-Rolled Round Steel and Square Steel GB 702-86
Hot-rolled round steel and square steel produced according to GB 702-86 is a kind of commodity bearing the features of high strength and good weld ability, low carbon content, and good toughness and superior machinability, making it suitable for a lot of fabrication and manufacturing processes with enhanced fatigue resistance and good stability in dynamic loading conditions. It is widely used in various engineering structures, such as automobile components, machinery parts, agricultural machinery, and construction equipment, etc.
GB 702-86 refers to a set of national standard regarding hot-rolled round steel and square steel. According to the standard, hot-rolled round steel and square steel must have a uniform distribution of cross-sectional area profile, their sectional dimension should meet the specific ranges, and their surface quality should also be in accordance to the standard, with no more than four allowed defects.
Hot-rolled round steel and square steel all have different range of size and shape requirements. According to the standard’s size range requirements, hot-rolled round steel and square steel should have a diameter of 10 to 50 mm, and the wall thickness should range from 3 to 10 mm, with maximum edge deviation of 0.15 mm allowed. The size range for hot-rolled square steel is not specifically designated in the standard, but its size should be within the range allowed by the standard for hot-rolled round steel.
In terms of its chemical composition, hot-rolled round steel and square steel should mainly be composed of carbon, manganese, phosphorus, sulfur, copper, copper, and phosphorus. The amount of carbon should not exceed 0.25%, and the amount of manganese should be between 0.60 and 0.90%. Moreover, the content of phosphorus and sulfur should be less than 0.035%.
When it comes to the mechanical properties of hot-rolled round steel and square steel, the requirements of GB 702-86 are that they should have a yield strength range of not lower than 245 MPa, an elongation percentage range of not lower than 24%, and a tensile strength range of not lower than 320 MPa.
In terms of its production process and methods, according to the national standard, hot-rolled round steel and square steel should be produced with a hot rolling process, which involves heating the steel at an appropriate temperature and then rolling it into shape through a number of sequenced steps. As for the finishing process, it should include surface cleaning, oiling, the testing of the microstructure of the material, and surface finishing by phosphating or other processes.
In conclusion, hot-rolled round steel and square steel produced according to GB 702-86 standard have a uniform cross-sectional area profile and meet certain dimensional, chemical and mechanical requirements. The production process and method of the hot-rolled round steel and square steel should be hot rolling with a finishing process including surface cleaning, oiling, and microstructure testing, etc. Therefore, the use of hot-rolled round steel and square steel produced in accordance with the national standard can ensure the engineering structure’s quality, stability and durability.
