GB/T 35741-2017 in English

GB/T 35741—2017 Technical conditions for stainless steel forgings for industrial valves

Standard overview

This standard specifies the structural form, technical requirements, test methods, inspection rules, marking and quality certificates, as well as protection, packaging, storage and transportation of stainless steel forgings for industrial valves. It is applicable to pressure-bearing stainless steel forgings for industrial valves.

Structural forms

This standard specifies a variety of structural forms, including: cylindrical forgings, ring forgings, pancake forgings, bowl forgings, long-neck flange forgings, strip forgings and valve body forgings, which are suitable for valve components in different parts.

Technical requirements

Chemical composition and mechanical properties

The chemical composition of stainless steel forgings is shown in Table 1, and the mechanical properties are shown in Table 2. Key indicators include:

• Tensile strength: ≥159 MPa
• Yield strength: ≥120 MPa
• Impact absorption energy: ≥78 J
• Grain size requirements: not less than Grade 7 specified in Table 6 of GB/T6394-2017

Forging and heat treatment

Forgings should be forged on a forging press with sufficient capacity, and the internal structure should be uniform and dense. The forging ratio of the main section should not be less than 3 (billet) or 2 (rolled material). The heat treatment state is recommended in Table 2.

Non-destructive testing

Liquid penetrant testing and ultrasonic testing are carried out in accordance with the provisions of JB/T6902-2008 and JB/T6903-2008 respectively to ensure that there are no defects such as cracks and interlayers on the surface of the forgings.

Implementation Recommendations

Material Selection and Processing

Select appropriate stainless steel grades (such as 06Cr19Ni10, 022Cr17Ni12Mo2, etc.) according to the working conditions of the valve. During the processing, attention should be paid to the control of forging ratio and heat treatment temperature to ensure that the mechanical properties meet the standards.

Inspection and Acceptance

Factory inspection should include dimensional inspection, chemical composition analysis and mechanical properties testing. Process evaluation inspection should be carried out when new products are trial-formed or production conditions are changed.

Quality Control

It is recommended that enterprises establish a complete quality control system to ensure that the surface quality and internal structure of forgings meet the standard requirements. Pay special attention to key indicators such as grain size, ferrite content and intergranular corrosion.