The standard refers to the American ASTM or ASME standard with new and unique technical clauses added, which is suitable for a type of petrochemical fasteners used in high temperature and high-pressure environments, including bolts, studs, nuts, etc.
The mechanical properties and materials specified in GB/T3098/8 "Mechanical Properties of Carbon Steel Fasteners Part VIII Heat-resistant Threaded Connections" are suitable for fasteners that can withstand high temperature, alternating loads, and to a greater extent. Be sure to tighten the axial force.
High temperature and high-pressure petrochemical fasteners - commodity fasteners and special fasteners
●The type and size of hexagon head bolts meet the requirements of GB/T5782, A and B grades. The mechanical properties of these petrochemical fasteners refer to the performance grades of carbon steel bolts according to GB/T3098/1 standard: A2-50, A4-50, A2-70, A4-70;
●The nut type conforms to GB/T6170 I-type nut and special nut (pipe flange nut). Its mechanical properties refer to the performance grades of carbon steel according to the GB/T3098/2 standard: grades 6 and 8; the performance grades of stainless steel nuts of GB/T3098/15 are A2-50, A4-50, A2-70, A4-70 ;
●In order to be suitable for the conditions of high-temperature resistance, low-temperature resistance, and environmental corrosion resistance, formulate suitable special fasteners, such as full-threaded studs for pipe flanges, in accordance with the provisions of GB/T901. The dimensions of hexagon head bolts and nuts shall be carried out according to national standards.
●Selected materials (grades) include medium carbon alloy steels: 35CrMo (applicable temperature +100-525℃); 25Cr2MoV (applicable temperature>-20--575℃); 42 CrMo (applicable temperature +100-525℃). The strength is between 690~890Mpa, that is to say, the medium carbon alloy steel is tempered at high temperature (550℃<=tempering temperature<=600℃) to obtain comprehensive mechanical properties to meet the service of high-temperature environment.
●Stainless steel materials selected are: 0Cr18Mi9 (applicable temperature -196--800 ℃); 0Cr17Mi12Mo2 (applicable temperature +196--800 ℃); the strength of stainless steel material obtained by solution treatment is between 690~890Mpa, and the performance level is A2- 70 A4-50 A4-80 grade.
●Using American standards, using stainless steel grades and materials: ASTM A193 B8 CL.2 (for temperature +196-525℃); A193 B8M CL.2 (for temperature +196-525℃); A453660 (for temperature +29- 525℃); also includes A320L7 suitable for low temperature and high-pressure environment (applicable temperature -100℃).
●Special grade nut material (grade) can choose medium carbon alloy steel: 30CrMo, 35CrMo; guaranteed load