Selection of forging grade

Refer to HGT 20581

Everyone, please discuss actively; I don’t understand: lol

There are many regulations, and one should gradually accumulate knowledge on them. First, take a look at your company’s rules to determine what level should be used in different situations; the standards are often specified in certain places

For use on pressure vessels, the minimum requirement is Grade II

Giving a specific example should allow for a concrete answer: (

GB150.2-2011 \"Pressure Vessels – Part 2: Materials\" 6.1 Carbon and low-alloy steel forgings 6.1.3 The grade of steel forgings is specified by the design and indicated on the drawings (by adding a grade symbol after the steel grade, such as 16Mn Ⅱ, 09MnNiD Ⅲ). The following steel forgings should be selected from grade III or IV: a) cylindrical, annular, and bowl-shaped forgings used as vessel shells and heads ； b) Low-alloy steel forgings with a nominal thickness greater than 300 mm ； c) Low-alloy steel forgings with a minimum standard tensile strength of 540 MPa or higher and a nominal thickness of more than 200 mm ； d) Low-temperature steel forgings with a service temperature below -20°C and a nominal thickness greater than 200 mm. 6.2 High-alloy steel forgings 6.2.3 The grade of the steel forgings is specified by the design and indicated on the drawing (the grade symbol is appended after the steel grade, such as S30408 Ⅱ). Cylindrical, annular, and bowl-shaped forgings used for container shells and heads should be of grade III or IV. HG/T 20592-2009 “Steel pipe flanges”. 4.0.2 The grades and technical requirements of forgings (including rolled forgings) used for pipe flanges shall comply with the provisions of the following two items. 1 Those that meet one of the following conditions shall comply with the requirements for grade III or higher forged parts: 1) Those with a nominal pressure greater than or equal to PN100 ； 2) Chromium-molybdenum steel forgings with a nominal pressure greater than PN40 ； 3) Ferritic steel forgings with a nominal pressure greater than PN16 and an operating temperature of less than or equal to -20°C. 2 Except as specified above, forgings with a nominal pressure not exceeding PN63 shall meet the requirements for grade II or higher forgings. Of course, the American system also has corresponding regulations regarding flanges. HG/T 20581-2011 “Regulations on the Selection of Materials for Steel Chemical Containers”. 6.4.2 Forgings whose dimensions and mass meet one of the following conditions are considered small- and medium-sized forgings; those exceeding these conditions are regarded as large-sized forgings. 1 Manway flanges with a flange size not exceeding PN2.5, DN600, or other ring forgings equivalent to such sizes. 2. Cake-shaped, cylindrical, and special-shaped forgings with a mass of no more than 800 kg (such as tees, valve bodies, etc.). 3 Bar or shaft forgings with a diameter not exceeding 200 mm and a mass not exceeding 1500 kg. 6.4.3 For forgings used in pressure vessels, the appropriate forging grade shall be selected based on their operating conditions as well as size and mass. 1 Flanges with a design pressure of less than 10.0 MPa, as well as forgings with similar geometric dimensions, shall meet the requirements of Grade II or above. 2 For forgings with a design pressure of 1.6 MPa or higher, they shall meet the requirements of Grade II or above. 3 Small and medium-sized forgings with a design pressure of 10.0 MPa or higher shall meet Class III requirements, while large forgings shall meet Class III or Class IV requirements. 4 For forgings with extremely or highly hazardous media toxicity, as well as forgings with a nominal thickness greater than 300 mm, Class III or Class IV requirements shall apply. HG/T20585-2011 \"Technical Specifications for Steel Cryogenic Pressure Vessels\" 6.0.8 For forgings used in cryogenic pressure vessels, the requirements specified in \"Low-Alloy Steel Forgings for Cryogenic Pressure Equipment\" NB/T 47009 and \"Stainless Steel and Heat-Resistant Steel Forgings for Pressure Equipment\" NB/T 47010 shall be met; these requirements shall be at least at level II. When the design pressure is 1.60 Mpa or higher, the required standard shall be at least level III. The above are the most commonly used choices for forging grades

Hey, make sure to design things properly; if you don’t understand something, ask for help. Don’t create difficulties for the procurement team, haha

The forging grade of the flange can be determined by referring to the corresponding flange standards, such as HG/T20592-20634