GB/T 21237-2018 (English Version)

Standard No.: GB/T 21237-2018
Language: Chinese, Available in English version
Release Date: 2018
Published By: General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Latest: GB/T 21237-2018
Replace: GB/T 21237-2007

Scope: This standard specifies the classification and designation method, size, shape, weight, technical requirements, test methods, inspection rules, packaging, marks and quality certificates of wide and thick steel plates for oil and natural gas pipelines. This standard applies to wide and thick steel plates (hereinafter referred to as steel plates) with a thickness of 6 mm to 50 mm for oil and natural gas pipelines produced in accordance with ISO 3183, GB/T 9711 and API Spec 5L. Wide and thick steel plates for other fluid transport welded pipes can also be used. Refer to this standard.

Introduction

Key points of standard core changes

Technical dimension	2007 edition	2018 edition
Thickness range	Unspecified upper limit	6-50mm
Quality grade	Single grade	PSL1/PSL2 dual system
Grade system	Classification by strength	Strength + delivery status composite identification
High-strength steel grades	X80 is the highest	Newly added X90M/X120M

Key technological innovations

1. Dual-track quality grade system

PSL2 grade steel plates have added 6 new control indicators, including grain size and non-metallic inclusions:

Grain size of steel for gas transmission pipes must reach No.10 grade (X70 and above)
Non-metallic inclusions, fine/coarse, are both ≤2.0
Banded structure ≤3 grade (X80 and below)

2. New rules for carbon equivalent calculation

Different formulas are used for different carbon contents:

Carbon content	Calculation formula	Control index
≤0.12%	CE_pcm=C+Si/30+(Mn+Cu+Cr)/20+Ni/60+Mo/15+V/10+5B	≤0.25%
＞0.12%	CE_IIW=C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15	≤0.43%

Typical case: class=instrument>X120M adopts ultra-low carbon design (C≤0.10%), and achieves CE_pcm≤0.25

through TMCP process

Implementation suggestions

Material selection guidance

High-voltage trunk line: PSL2 grade X80M/X90M is preferred, and DWTT shear area ≥85%
Low temperature environment: Charpy impact must meet the average value of ≥180J at -20℃ (X100M)
Acidic medium: Add Cu≤0.3% and control HV10≤240

Key points of process control

Process	Key parameters	Monitoring method
Smelting	Vacuum degassing (X70+)	Oxygen and nitrogen analyzer
Rolling	Final rolling temperature ±15℃	Infrared temperature measurement
Heat treatment	Q&T process tempering temperature control	Thermocouple calibration

GB/T 21237-2018 Referenced Document

GB/T 10561 Standard grading chart microscopic examination method for determination of non-metallic inclusion content in steel*， 2023-05-23 Update
GB/T 13299 Determination of free cementite, pearlite and Widmanstaten structure in steel*， 2022-07-11 Update
GB/T 14977 General requirement for surface condition of hot-rolled steel plates
GB/T 17505 Steel and steel products.General technical delivery requirements
GB/T 20066 Steel and iron.Sampling and preparation of samples for the determination of chemical composition
GB/T 20123 Steel and iron - Determination of total carbon and sulfur content Infrared absorption method after combustion in an induction furnace (routine method)
GB/T 20125 Low-alloy steel.Determination of multi-element contents.Inductively coupled plasma atomic emission spectrometric method
GB/T 223.12 Methods for chemical analysis of iron,steel and alloy--The sodium carbonate separation-diphenyl carbazide photometric method for the determination of chromium content
GB/T 223.16 Methods for chemical analysis of iron,steel and alloy--The chromotropic acid photometric method for the determination of titanium content
GB/T 223.19 Methods for chemical analysis of iron,steel and alloy--The neocuproine-chloroform extraction photometric method for the determination of copper content
GB/T 223.26 Iron,steel and alloy.Determination of molybdenum content.The thiocyanate spectrophotometric method
GB/T 223.40 Iron, steel and alloy Determination of niobium content by the sulphochlorophenol S spectrophotometric method
GB/T 223.5 Steel and iron.Determination of acid-soluble silicon and total silicon content.Reduced molybdosilicate spectrophotometric method
GB/T 223.54 Iron, steel and alloy—Determination of nickel content—Flame atomic absorption spectrometric method*， 2022-07-11 Update
GB/T 223.58 Methods for chemical analysis of iron,steel and alloy--The sodium arsenite-sodium nitrite titrimetric method for the determination of manganese content
GB/T 223.59 Iron,steel and alloy.Determination of phosphorus content.Bismuth phosphomolybdate blue spectrophotometic method and antimony phosphomolybdate blue spectruophotometric method
GB/T 223.68 Methods for chemical analysis of iron, steel and alloy. The potassium iodate titration method after combustion in the pipe furnace for the determination of sulfur content
GB/T 223.69 Iron,steel and alloy.Determination of carbon contents.Gas-volumetric method after combustion in the pipe furnace
GB/T 223.76 Methods for chemical analysis iron,steel and alloy.The flame atomic absorption spertrometric method for the determination of vanadium content
GB/T 223.78 Methods for chemical analysis of iron,steel and alloy-Curcumin spectrophotometric method for the determination of boron content
GB/T 228.1 Metallic materials—Tensile testing—Part 1: Method of test at room temperature*， 2021-12-31 Update
GB/T 229 Metallic materials—Charpy pendulum impact test method*， 2020-09-29 Update
GB/T 232 Metallic materials - Bend test methods*， 2024-03-15 Update
GB/T 247 General rule of package,mark and certification for steel plates(sheets)and strips
GB/T 2975 Steel and steel products - Location and preparation of samples and test pieces for mechanical testing
GB/T 4336 Determination of multi-element content in carbon steel and medium and low alloy steel Spark discharge atomic emission spectrometry (conventional method) Amendment No. 1
GB/T 4340.1 Vickers hardness test for metallic materials Part 1: Test method*， 2024-05-28 Update
GB/T 6394 Determination of estimating the average grain size of metal
GB/T 709 "Dimension,shape,weight and tolerance for hot rolled steel strip,plate and sheet"*， 2019-03-25 Update
GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values
GB/T 8363 Steel—Drop-weight tear tests method

GB/T 21237-2018 history

2018 GB/T 21237-2018 Wide and heavy plates for line pipe of petroleum and natural gas
2007 GB/T 21237-2007 Wide and heavy plates for line pipe of petroleum and natural gas