GB/T 38682-2020 in English

Interpretation of the core content of the standard

Details of key technical requirements

Material characteristics

The standard covers three alloys: NS1101, NS1102, and NS1104, with chromium content of 19.0-23.0%, nickel content of 30.0-35.0%, and corrosion resistance is enhanced by elements such as molybdenum and titanium. In particular, the Al+Ti content of NS1104 must be controlled at 0.85-1.20%.

Manufacturing process

The welded pipe needs to be solution treated at 1040-1150℃ and quickly cooled. HNS3106 welding wire is recommended. The weld reinforcement is strictly controlled. When the nominal outer diameter is <219mm, the inner weld reinforcement is ≤10% of the wall thickness and ≤1.5mm.

Testing and certification system

• Non-destructive testing:Outer diameter＞168.3mm requires 100% radiographic testing (AB grade/Ⅱ grade)
• Compactness test:Hydraulic test or eddy current testing (E4H/E4 grade)
• Special testing:High-temperature tensile test, hardness test and other items can be added through negotiation

Implementation suggestions

Selection guide

In high temperature environment (＞590℃), NS1102/NS1104 is preferred; in complex corrosive media working conditions, the excellent anti-intergranular corrosion ability of NS1104 should be considered.

Main points for quality control

1. Strictly monitor the temperature curve of post-weld heat treatment
2. 100% penetration test should be conducted on the weld area
3. Batch acceptance should be graded and grouped according to outer diameter (maximum 400 pieces/batch)