My country's petrochemical industry proposed HG/T50634-2009 "Fasteners for Steel Pipe Flanges". This standard refers to the American ASTM or ASME standard and adds new and unique technical clauses. It is suitable for a class of fastener products 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 8 Heat-resistant Threaded Connections" are suitable for fasteners that can withstand high temperatures and alternating loads, and to a greater extent Be sure to tighten the axial force.
High temperature and high pressure fasteners are divided into commodity fasteners and special fasteners
Common commodity fasteners:
●The type and size of the hexagon head bolts conform to the requirements of GB/T5782, Class A and Class B. Its mechanical properties are based on the performance grades of carbon steel bolts in accordance with the GB/T3098/1 standard: A2-50, A4-50, A2-70, A4-70;
●The nut type conforms to GB/T6170I type nut and special nut (pipe flange nut). Its mechanical properties refer to the performance levels of carbon steel in GB/T3098/2 standards: 6 and 8; GB/T3098/15 stainless steel nuts performance levels A2-50, A4-50, A2-70, A4-70 ；
special fasteners
● In order to apply the conditions of high temperature resistance, low temperature resistance and environmental corrosion resistance, the appropriate special fasteners, such as full-threaded studs for pipe flanges, shall be formulated in accordance with the provisions of GB/T901. The size of hexagon head bolts and nuts are implemented in accordance with national standards.
●The selected materials (grades) are medium carbon alloy steel: 35CrMo (applicable temperature +100-525℃); 25Cr2MoV (applicable temperature >-20--575℃); 42CrMo (applicable temperature +100-525℃). The strength is between 690 and 890Mpa, which means that medium-carbon alloy steel is tempered with high temperature (550℃<=tempering temperature<=600℃) to obtain comprehensive mechanical properties to meet high temperature environment service.
●The selection of stainless steel materials are: 0Cr18Mi9 (applicable temperature -196--800℃); 0Cr17Mi12Mo2 (applicable temperature +196--800℃); the strength of stainless steel materials is between 690~890Mpa after solution treatment, and the performance level is A2- 70A4-50A4-80 grade
●Using American standards, using stainless steel grades and materials: ASTMA193B8CL.2 (temperature applicable +196-525°C); A193B8MCL.2 (temperature applicable +196-525°C); A453660 (temperature applicable +29-525°C); Including A320L7 suitable for low temperature and high pressure environment (applicable temperature -100℃).
●Special grade nut material (grade) can be selected from medium-carbon alloy steel: 30CrMo, 35CrMo; guaranteed load.
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