H 46
N ation al stand ar d o f t h e Pe op le ’s R epu b li c o f ch in a
GB/T 1591—2008
Supersedes GB/T 1591-1994High Strength Low Alloy Structural
Steels
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Foreword
This standard has been prepared by revising GB/T 1591-1994 High strength low alloy structuaral steels and referring to EN10025:2004 Hot rolled products of structural steels.
This standard supersedes GB/T 1591-1994 High strength low alloy structuaral steels. Compared with the previous version, changes are made as follows:
— Expanded applicable scope;
— Added strength grade Q500, Q620, Q690 and cancelled strength grade Q295;
— Modified the requirements for chemical composition of steel products, requiring some serious control to some harmful elements such as P and S.
— Added the requirements for CEV and Pcm and their corresponding calculation formulas of CEV and Pcm.
— Modified the delivery condition of steel products and cancelled the requirements for quenched and tempered steel products.
— Modified the requirements for the values of mechanical properties and thickness range, making clear that the yield strength in text refer to the lower yield strength.
— Increased the specified impact absorbed energy value.
— Added the requirements for through-thickness characteristics of steel products. This standard was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of National Standardization Technical Committee of Steel.
This standard was drafted by Angang Steel Co., Ltd, China Metallurgical Information and Standardization Institute, Jigang Group Co., Ltd, Shougang Group, Shagang Group Co.,Ltd, Hualing Lianyuan Iron and Steel CO.,Ltd.
The main drafters of this standard: Liu Xuyuan, Piao Zhimin, Wang Xiaohu, Gao Ling, Wang Liping, Huang Zhengyu, Zhou Jian, Ma Yupu, Chen Shouqing.
The superseded editions of this standard are as follows: — GB 1591-1979, GB 1591-1988, GB/T 1591-1994.
High Strength Low Alloy Structural Steels
1 Scope
This standard specifies the designation, dimensions, tolerances on dimensions and shape, mass, technical requirements, test methods, inspection, packaging, marking and certification of high strength low alloy steels.
This standard applies to the steel sheet, steel strip, sections and bars of high strength low alloy steels for general structure and engineering services.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this national standard are encouraged to investigate the possibility of applying the most recent editions of the standard indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 222 Permissible tolerances for chemical composition of steel products
GB/T 223.5 Steel and iron - Determination of acid-soluble silicon and total silicon content-Reduced molybdosilicate spectrophotometric method
GB/T 223.9 Iron, steel and alloy-Determination of aluminium content - Chrome azurol S photometric 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 223.14 Methods for chemical analysis of iron, steel and alloy - The
N-benzoy-N-phenylhydroxylamine extraction photometric method for the determination of vanadium 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 223.23 Iron, steel and alloy - Determination of nickel content – The dimethylglyoxime spectrophotometric method
GB/T 223.26 Iron, steel and alloy - Determination of molybdenum content – The thiocyanate spectrophotometric method
GB/T 223.37 Methods for chemical analysis of iron, steel and alloy – The indophenol blue photometric method for the determination of nitrogen content after distillation separation GB/T 223.40 Iron, steel and alloy - Determination of niobium content - The sulphochlorophenol
GB/T 1591—2008
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S spectrophotometric method
GB/T 223.62 Methods for chemical analysis of iron, steel and alloy - The butyl acetate extraction photometric method for the determination of phosphorus content
GB/T 223.63 Methods for chemical analysis of iron, steel and alloy - The sodium (potassium) periodate photometric method for the determination of manganese content
GB/T 223.67 Iron, steel and alloy – Determination of sulfur content – Methylene blue spectrophotometric metrod
GB/T 223.69 Iron, steel and alloy - Determination of carbon contents - Gas-volumetric method after combustion in the pipe furnace
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 Metallic materials - Tensile testing at ambient temperature(GB/T 228-2002，eqv ISO 6892:1998)
GB/T 229 Metallic materials - Charpy pendulum impact test method（GB/T 229-2007, ISO 148-1:2006, MOD）
GB/T 232 Metallic materials - Bend test（GB/T 232-1999, eqv ISO 7438:1985）
GB/T 247 General rule of package, mark and certification for steel plates(sheets) and strips GB/T 2101 General requirement of acceptance, packaging, marking, and certification for section steel
GB/T 2975 Steel and steel products - Location and preparation of test pieces for mechanical testing（GB/T 2975-1998, eqv ISO 377:1997）
GB/T 4336 Standard test method for spark discharge atomic emission - Spectrometric analysis of carbon and low alloy steel (routine method )
GB/T 5313 Steel plate with through-thickness characteristics
GB/T 17505 Steel and steel products - General technical delivery requirements（GB/T 17505-1998, eqv ISO 404:1992）
GB/T 20066 Steel and iron - Sampling and preparation of samples for the determination of chemical composition（GB/T 20066-2006，ISO 14284：1996,IDT）
GB/T 20125 Low-alloy steel - Determination of multi-element contents – Inductively coupled plasma atomic emission spectrometric method
YB/T 081 Rule for rounding off of numberical values and judgement of testing values for technical standards of metallurgy
3 Terms and definitions
3.1
thermomechanical rolling
rolling process in which the final deformation is carried out in a certain temperature range leading to a material condition with certain properties which cannot be achieved or repeated by heat treatment alone
NOTE1：Subsequent heating above 580 C may lower the strength values. If temperatures above 580 C are needed reference should be made to the supplier.
NOTE2：Thermomechanical rolling can include processes with an increasing cooling rate with or without tempering including self-tempering but excluding direct quenching and quenching and tempering.
3.2
normalizing rolling
rolling process in which the final deformation is carried out in a certain temperature range leading to a material condition equivalent to that obtained after normalizing so that the specified values of the mechanical properties are retained even after normalizing.
4 Designation
The designation shall consist of bopomofo for yield strength, value of yield strength and symbol for quality grade, such as Q345D. Thereinto:
Q — first bopomofo for chinese for yield strength; 345 — value of yield strength,MPa;
D — quality grade D.
If the purchaser requires through-thickness characteristics of a steel product, the additional symbol Z for the suitability for through-thickness characteristics shall be added, such as Q345DZ15.
5 Dimensions, tolerances on dimensions and shape, mass
Dimensions, tolerances on dimensions and shape, mass shall be in accordance with the requirements of relevant documents.
6 Technical requirements
6.1 Steel designation and chemical composition
6.1.1 The steel designation and chemical composition determined by ladle analysis shall comply with the specified values of Table 1.
6.1.2 If the grain-refining elements are required, the steels contain at least one of these elements such as Al, Nb, V and Ti. If the grain-refining elements are added, they shall be reported in the inspection document.
6.1.3 If the total content of Al is determined, the Al total (Alt) shall be not less than
0.020%.
6.1.4 The nitrogen content of steels shall comply with the specified values of Table 1. If the manufacturer can make sure that the nitrogen content is suitable, the nitrogen content may no longer be determined.The maximum value for nitrogen does not apply if the N binding elements including Al, Nb, V or Ti are added. In this case the N binding elements shall be reported in the inspection document.
6.1.5 If Cr, Ni or Cu in steel is added as the remaining elements, the content of each element shall be no more than 0.30%. If the manufacturer can make sure that content of each of these elements is suitable, each content may no longer be determined. If Cr, Ni or Cu is added
GB/T 1591—2008
4
intentionally, each element shall comply with the specified values of Table 1 or agreement between the purchaser and manufacturer.
6.1.6 In order to improve the property of steel, rare earth elements may be added, with 0.02%～0.20% of the steel mass.
6.1.7 If the mechanical properties of steel products can be in accordance with the requirements of this document, the content of C, Si and Mn of quality grade A of all steels may be not required.
Table1 Chemical composition of the ladle analysis
Design -ation Quality grade Chemical composition a, b ( mass fraction)/% C max. Si max. Mn max. P max. S max. Nb max. V max. Ti max. Cr max. Ni max. Cu max. N max. Mo max. B max. Als min. Q345 A 0.20 0.50 1.70 0.035 0.035 0.07 0.15 0.20 0.30 0.50 0.30 0.012 0.10 - - B 0.035 0.035 C 0.030 0.030 0.015 D 0.18 0.030 0.025 E 0.025 0.020 Q390 A 0.20 0.50 1.70 0.035 0.035 0.07 0.20 0.20 0.30 0.50 0.30 0.015 0.10 - - B 0.035 0.035 C 0.030 0.030 0.015 D 0.030 0.025 E 0.025 0.020 Q420 A 0.20 0.50 1.70 0.035 0.035 0.07 0.20 0.20 0.30 0.80 0.30 0.015 0.20 - - B 0.035 0.035 C 0.030 0.030 0.015 D 0.030 0.025 E 0.025 0.020 Q460 C 0.20 0.60 1.80 0.030 0.030 0.11 0.20 0.20 0.30 0.80 0.55 0.015 0.20 0.004 0.015 D 0.030 0.025 E 0.025 0.020 Q500 C 0.18 0.60 1.80 0.030 0.030 0.11 0.12 0.20 0.60 0.80 0.55 0.015 0.20 0.004 0.015 D 0.030 0.025 E 0.025 0.020 Q550 C 0.18 0.60 2.00 0.030 0.030 0.11 0.12 0.20 0.80 0.80 0.80 0.015 0.30 0.004 0.015 D 0.030 0.025 E 0.025 0.020 Q620 C 0.18 0.60 2.00 0.030 0.030 0.11 0.12 0.20 1.00 0.80 0.80 0.015 0.30 0.004 0.015 D 0.030 0.025 E 0.025 0.020 Q690 C 0.18 0.60 2.00 0.030 0.030 0.11 0.12 0.20 1.00 0.80 0.80 0.015 0.30 0.004 0.015 D 0.030 0.025
E 0.025 0.020 a
For sections and bars, the P and S content can be 0.005% higher. For quality grade A of steels, the maximum S and P content can be 0.045%.
b
If the grain-refining elements such as Nb, V, Ti are used in combination: the sum of Nb, V and Ti concentrations shall be no more than 0.22%, the sum of Mo and Cr concentrations shall be no more than 0.30%.
6.1.8 The maximum carbon equivalent values of the steels other than quality grade A shall comply with the specified values of table 2 for as-rolled or controlled rolling delivery condition; for normalizing, normalizing rolling or normalizing plus tempering delivery condition, shall comply with the specified values of table 3; for thermomechanical rolling (TMCP) or thermomechanical rolling plus tempering delivery condition, shall comply with the specified values of table 4. For determining the carbon equivalent (CEV) based on the ladle analysis, the following formula (1) shall be used.
15 ) ( 5 ) ( 6 Cu Ni v Mo Cr Mn C CEV ... (1)
Table2 Maximum CEV for as-rolled or controlled rolled steel
Designation Maximum CEV in % for nominal product thickness in mm
≤63 ＞63～250 ＞250
Q345 0.44 0.47 0.47
Q390 0.45 0.48 0.48
Q420 0.45 0.48 0.48
Q460 0.46 0.49 —
Table3 Maximum CEV for normalized 、normalized rolled or normalized rolled ＋tempered steel
Designation Maximum CEV in % for nominal product thickness in mm
≤63 ＞63～120 ＞120～250
Q345 0.45 0.48 0.48
Q390 0.46 0.48 0.49
Q420 0.48 0.50 0.52
Q460 0.53 0.54 0.55
Table4 Maximum CEV for thermomechanical rolled or thermomechanical rolled ＋ tempered steel
Designation Maximum CEV in % for nominal product thickness in mm
≤63 ＞63～120 ＞120～150
Q345 0.44 0.45 0.45
Q390 0.46 0.47 0.47
GB/T 1591—2008 6 Q460 0.47 0.48 0.48 Q500 0.47 0.48 0.48 Q550 0.47 0.48 0.48 Q620 0.48 0.49 0.49 Q690 0.49 0.49 0.49
6.1.9 For the thermomechanical rolling or thermomechanical rolling plus tempering delivery condition, the carbon equivalent, CEV of steels with a ladle analysis carbon mass fraction equal to or less than 0.12% can be superseded by welding crack susceptibility index, Pcm. The Pcm shall comply with the specified values of table 5. For determining the Pcm based on the ladle analysis, the following formula (2) shall be used.
B V Mo Cr Ni Cu Mn Si C Pcm 5 10 15 20 60 20 20 30 ... (2)
It shall be as agreed that whether CEV or Pcm is used .If unspecified at the time of the order, it is left to the discretion of the manufacturer to use whether CEV or Pcm.
Table5 Maximum Pcm for thermomechanical rolled or thermomechanical rolled ＋ tempered steel
Designation Pcm/% Q345 0.20 Q390 0.20 Q420 0.20 Q460 0.20 Q500 0.25 Q550 0.25 Q620 0.25 Q690 0.25
6.1.10 The permissible tolerances for the product analysis shall comply with the specifications given in GB/T 222.
6.1.11 If the purchaser requires the steel products with through-thickness characteristics, the chemical composition of these steel products shall comply with the specified values given in GB/T 5313.
6.2 Steel making process
The steel shall be manufactured using the electric process or an oxygen process. If necessary, the secondary refining shall be used.
6.3 Delivery condition
The delivery condition can be as-rolled, controlled rolling, normalizing, normalizing rolling, normalizing plus tempering, thermomechanical rolling or thermomechanical rolling plus tempering.
6.4 Mechanical properties 6.4.1 Tensile test
The tensile properties of steels shall comply with the specified values of table 6. Table6 Mechanical properties of steels
Design -ation
Quality grade
Tensile test a, b, c
Minimum yield strength Rel/MPa Tensile strength Rm/MPa
Minimum percentage elongation after fracture/%
Nominal thickness/mm Nominal thickness/mm Nominal thickness/mm
≤16 ＞16 ～40 ＞40 ～63 ＞63 ～80 ＞80 ～100 ＞100 ～150 ＞150 ～200 ＞200 ～250 ＞250 ～400 ≤40 ＞40 ～63 ＞63 ～80 ＞80 ～100 ＞100 ～150 ＞150 ～250 ＞250 ～400 ≤40 ＞40 ～63 ＞63 ～100 ＞100 ～150 ＞150 ～250 ＞250 ～400 Q345 A 345 335 325 315 305 285 275 265 - 470～ 630 470～ 630 470～ 630 470～ 630 450～ 600 450～ 600 - 20 19 19 18 17 - B C 21 20 20 19 18 D 265 450～ 600 17 E Q390 A 390 370 350 330 330 310 - - - 490～ 650 490～ 650 490～ 650 490～ 650 470～ 620 - - 20 19 19 18 - - B C D E Q420 A 420 400 380 360 360 340 - - - 520～ 680 520～ 680 520～ 680 520～ 680 500～ 650 - - 19 18 18 18 - - B C D E Q460 C 460 440 420 400 400 380 - - - 550～ 720 550～ 720 550～ 720 550～ 720 530～ 700 - - 17 16 16 16 - - D E Q500 C 500 480 470 450 440 - - - - 610～ 770 600～ 760 590～ 750 540～ 730 - - - 17 17 17 - - - D E Q550 C 550 530 520 500 490 - - - - 670～ 830 620～ 810 600～ 790 590～ 780 - - - 16 16 16 - - - D E Q620 C 620 600 590 570 - - - 710～ 880 690～ 880 670～ 860 - - - - 15 15 15 - - - D E Q690 C 690 670 660 640 - - - 770～ 940 750～ 920 730～ 900 - - - - 14 14 14 - - D
GB/T 1591—2008
8 E a
If a definite yield phenomenon is not present, the lower yield strength can be measured by 0.2% offset Rp0.2.
b
For flat steel products with their widths not less than 600mm, the tensile test pieces shall be in the transverse direction. For sections, bars and flat steel products with their widths less than 600mm, the tensile test pieces shall be in the longitudinal direction, and the minimum percentage elongation after fracture shall be increased accordingly 1% (absolute value). c
The value for steels with thickness ＞250mm～400mm applies to flat steel products.
6.4.2 Charpy V-notch impact test
6.4.2.1 The test temperature and absorbed energy values of Charpy V-notch impact test of steels shall comply with the specified values of table 7.
6.4.2.2 The steel products with nominal thickness not less than 6mm or diameter not less than 12mm shall carry out the impact test. The standard 10mm×10mm×55mm test pieces shall be used. If the standard test pieces can not be obtained, the subsize test piece 10mm×7.5mm ×55mm or 10mm×5mm×55mm shall be used. If so, their minimum absorbed energy values shall comply respectively with 75% or 50% of the specified values of table 7. The bigger subsize test piece shall prevail.
6.4.2.3 The average value of the three test results shall meet the specified requirement. One individual value may be below the minimum average value specified, provided that it is not less than 70 % of that value. Otherwise three additional test pieces shall be taken from the same sample and tested. The average value of the six tests shall be not less than the minimum average value specified. Not more than two of the individual values may be lower than the minimum average value specified and not more than one may be lower than 70 % of this value. 6.4.3 The percentage reduction of area of steels with through-thickness characteristics shall comply with the specified values given in GB/T 5313.
Table7 Test temperature and absorbed energy for impact test (V-notch)
Designation Quality grade Test temperature/℃
Minimum absorbed energy a
KV2 /J Nominal thickness( diameter, border)/mm
12～150 ＞150～250 ＞250～400 Q345 B 20 34 27 - C 0 D -20 27 E -40 Q390 B 20 34 - - C 0 D -20 E -40 Q420 B 20 34 - - C 0 D -20 E -40 Q460 C 0 34 - - D -20
E -40 Q500、Q550、 Q620、Q690 C 0 55 - - D -20 47 E -40 31 a
The impact test pieces shall be in the longitudinal direction.
6.4.4 If specified at the time of the order the bend test shall be carried out. The bend properties of steels shall comply with the specified values of table 8. If the manufacturer can make sure that the bend properties of steel products is suitable, the bend test may be cancelled.
Table8 Bend test
Designation Piece direction
180°bend test
[d=bend diameter, a＝piece thickness (diameter)] Nominal thickness( diameter、border)/ mm
≤16 ＞16～100
Q345 Q390 Q420 Q460
For flat steel products with their widths not less than 600mm, the bend test pieces shall be in the transverse direction. For sections, bars and flat steel products with their widths less than 600mm, the bend test pieces shall
be in the longitudinal direction
2a 3a
6.5 Surface properties
The surface condition of steel products shall be in accordance with the requirements specified in relevant documents.
6.6 Specific requirement
6.6.1 According to the agreement between the purchaser and the manufacturer, the non-destructive testing may be carried out. The acceptance criteria and level shall be specified in the order or agreement.
6.6.2 According to the agreement between the purchaser and the manufacturer, the purchaser may require the steel products with through-thickness characteristics according to this document.
6.6.3 According to the agreement between the purchaser and the manufacturer, other tests may be carried out.
7 Test methods
The test item,test piece number,method for preparing test piece and test methods of steel products shall comply with the specified requirement of table 9.
GB/T 1591—2008
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Table9 Test item, sampling number and preparing method of test piece and test method
NO. Test item Test piece number Preparing methods Test methods
1 Chemical composition
( ladle analysis ) 1/furnace GB/T 20066
GB/T 223、GB/T 4336、 GB/T 20125
2 Tensile test 1/lot GB/T 2975 GB/T 228
3 Bend test 1/lot GB/T 2975 GB/T 232
4 Impact test 3/lot GB/T 2975 GB/T 229
5 through-thickness percentage
reduction of area 3/lot GB/T 5313 GB/T 5313
6 Non-destructive testing Each sheet or piece Relevant document for
non-destructive testing By agreement
7 Surface condition Each sheet or piece -
By visual inspection or
measuring equipment
8 Dimensions, shape Each sheet or piece -
By applicable measuring equipment
8 Inspection
8.1 Inspection and acceptance
The manufacturer shall be in charge of inspection and acceptance for steel products.The purchaser has the right to carry out inspection and acceptance tests specified in this document or the order.
8.2 Test units
The steel products shall be inspected and accepted by lot. Each lot shall contain products of the same designation,quality grade,furnace number,dimension,rolling condition or heat treatment condition. The mass of each lot of the steel product shall be not more than 60t.The mass of each lot of the steel strip shall be in accordance with specifications given in relenant document.
Each lot of steel products with quality grade A or B may contain steels of the same designation, quality grade, steelmaking process, cast method and different heat number, provided that different heats are not more than 6 and the difference of C and Mn content among the 6 heats shall be respectively not more than 0.22% and 0.15%.
For steels with through-thickness characteristics, each lot shall be in accordance with GB/T 5313.
8.3 Retest and acceptance criteria 8.3.1 Mechanical properties
If a set of charpy test pieces fail to meet the acceptance criteria specified in 6.4.2.3, the manufacturer may take respectively three additional test pieces from two more products from the same lot. If both of the new tests meet the acceptance criteria, then all products in that lot, with the exception of the original selected products, shall be considered to meet the requirement. Otherwise the steel products in that lot shall be rejected.
The retest and acceptance criteria for the tensile test of steel products shall be in accordance with GB/T 17505.
8.3.2 Retest and acceptance criteria for other test
The retest and acceptance criteria for other test of steel products shall be in accordance with GB/T 17505.
8.4 Rounding for test results of chemical composition and mechanical properties
Unless otherwise specified at the time of order or by agreement, to determine conformance with the specified requirements, observed or calculated values shall be rounded to the same number of digits as the specified value. The rules of rounding off for values shall be in accordance with YB/T 081. For the carbon equivalent, its vlaue shall be calculated acorrding to relevant formula and then shall be rounded off.
9 Packaging, marking, certification
The packaging,marking and certification for steel procucts ahall be in accordance with GB/T 247 or GB/T 2101.