Gbt 1591-2008_high Strength Low Alloy Structural Steel 2y2e40

ICS 77.140.10;77.140.50 H 46

National china

standard

of

the

People’s

Republic

of

GB/T 1591—2008

Supersedes GB/T 1591-199

High Strength Low Alloy Structural Steels 点击此处添加标准英文译名 点击此处添加与国际标准一致性程度的标识

     

Issue date: 2008-12-06

Implementation date: 2009-1001

I s s u e d b y G e n e r a l Ad m i n i s t ra t i o n o f Q u a l it y S u p e r v i s i o n , I n s p e c t i o n a n d Q u a ra n t i n e o f t h e P e o p l e ' s R e p u b li c o f C h i n a

GB/T 1591—2008

II

GB/T 1591—2008

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 The superseded editions of this standard are as follows: — GB 1591-1979, GB 1591-1988, GB/T 1591-1994.

I

GB/T 1591—2008

High Strength Low Alloy Structural Steels 1.1 　 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. 1.2 　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-Nphenylhydroxylamine 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 neocuproinechloroform 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 1

GB/T 1591—2008 GB/T 223.40 Iron, steel and alloy - Determination of niobium content - The sulphochlorophenol 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 2282002，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 1.3 　 and definitions 1.3.1 　 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

2

GB/T 1591—2008 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.

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. 1.4 　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. 1.5 　 Dimensions, tolerances on dimensions and shape, mass Dimensions, tolerances on dimensions and shape, mass shall be in accordance with the requirements of relevant documents. 1.6 　 Technical requirements 1.6.1 　 Steel designation and chemical composition The steel designation and chemical composition determined by ladle analysis shall comply with the specified values of Table 1. 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. If the total content of Al is determined, the Al total (Alt) shall be not less than 0.020%. 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. 3

GB/T 1591—2008 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 intentionally, each element shall comply with the specified values of Table 1 or agreement between the purchaser and manufacturer. In order to improve the property of steel, rare earth elements may be added, with 0.02% ～ 0.20% of the steel mass. 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

Qual

-ation

ity

C

Si

Mn

P

S

Nb

V

Ti

Cr

Ni

Cu

N

Mo

B

Als

grad

ma

ma

ma

max

max.

max.

max

max

max

max

max

max.

max.

max

min.

e

x.

x.

x.

.

.

.

.

.

.

0.

0.

1.

0.0

0.03

0.1

0.2

0.3

0.5

0.3

0.01

20

50

70

35

5

5

0

0

0

0

2

0.0

0.03

35

5

0.0

0.03

0.01

30

0

5

0.

0.0

0.02

18

30

5

0.0

0.02

25

0

Q345

A

Chemical composition

B C D E Q390

A

B C D 4

0.3

0.5

0.3

0.01

0

0

0

0

0

5

20

50

70

35

5

0.0

0.03

35

5

0.0

0.03

0.01

30

0

5

0.0

0.02

30

5

0.0

0.02

25

0 0.2

0.2

0.3

0.8

0.3

0.01

0

0

0

0

0

5

0.10

0.20

-

-

0.03

0.07

0.2

-

0.0

E

0.2

0.10

1.

D

A

.

0.

C

0.07

( mass fraction)/%

0.

B

Q420

0.07

a, b

-

-

0.

0.

1.

0.0

0.03

-

20

50

70

35

5

0.0

0.03

35

5

0.0

0.03

0.01

30

0

5

0.0

0.02

GB/T 1591—2008 E Q460

C

20

60

80

30

0

0.0

0.02

30

5

0.0

0.02

25

0

0.

0.

1.

0.0

0.03

18

60

80

30

0

0.0

0.02

30

5

0.0

0.02

25

0

0.

0.

2.

0.0

0.03

18

60

00

30

0

0.0

0.02

30

5

0.0

0.02

25

0

E C

0.

0.

2.

0.0

0.03

18

60

00

30

0

0.0

0.02

30

5

0.0

0.02

25

0

D E Q690

C D E

a

0 0.03

D

Q620

25 0.0

E C

0.02

1.

D

Q550

0.0 0.

E C

5

0.

D

Q500

30

0.

0.

2.

0.0

0.03

18

60

00

30

0

0.0

0.02

30

5

0.0

0.02

25

0

0.11

0.11

0.11

0.11

0.11

0.2

0.2

0.3

0.8

0.5

0.01

0

0

0

0

5

5

0.1

0.2

0.6

0.8

0.5

0.01

2

0

0

0

5

5

0.1

0.2

0.8

0.8

0.8

0.01

2

0

0

0

0

5

0.1

0.2

1.0

0.8

0.8

0.01

2

0

0

0

0

5

0.1

0.2

1.0

0.8

0.8

0.01

2

0

0

0

0

5

0.20

0.20

0.30

0.30

0.30

0.0

0.01

04

5

0.0

0.01

04

5

0.0

0.01

04

5

0.0

0.01

04

5

0.0

0.01

04

5

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%.

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 (TM) or thermomechanical rolling plus tempering delivery condition, shall comply with the specified values of table 4. For determining the 5

GB/T 1591—2008 carbon equivalent (CEV) based on the ladle analysis, the following formula (1) shall be used. CEV  C 

Mn (Cr  Mo  v ) ( Ni  Cu )   ...................... (1 ) 6 5 15

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

Q420

0.46

0.47

0.47

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

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. 6

GB/T 1591—2008 Si Mn Cu Ni Cr Mo V Pcm  C         5B 30 20 20 60 20 15 10

.................. (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

The permissible tolerances for the product analysis shall comply with the specifications given in GB/T 222. 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. 1.6.2 　 Steel making process The steel shall be manufactured using the electric process or an oxygen process. If necessary, the secondary refining shall be used. 1.6.3 　 Delivery condition The delivery condition can be as-rolled, controlled rolling, normalizing, normalizing rolling, normalizing plus tempering, thermomechanical rolling or thermomechanical rolling plus tempering. 1.6.4 　 Mechanical properties 1.6.4.1 　 Tensile test The tensile properties of steels shall comply with the specified values of table 6. Table6 　 Mechanical properties of steels Design

Q

-ation

u

　 Tensile test Minimum yield strength Rel/MPa

a, b, c

Tensile strength Rm/MPa

Minimum percentage

a

elongation after

l

fracture/%

i

Nominal thickness/mm

Nominal thickness/mm

Nominal thickness/mm

7

GB/T 1591—2008 t

≤

＞

＞

＞

＞

＞

＞

＞

＞

≤

＞

＞

＞

＞

＞

＞

≤＞

＞

＞

＞

＞

y

1

1

40

63

8

10

150

2

2

40

40

6

80

100

1

250

4

4

63

10

15

25

6

6

～

～

0

0

～

0

5

～

3

～

～

5

～

0 0

～

0

0

0

g

～

63

80

～

～

200

0

0

63

～

10

150

0

400

～

10

～

～

～

r

4

1

15

～

～

8

0

～

6

0

15

25

40

a

0

0

0

2

4

0

2

3

0

0

0

5

0

5

0

0

0

2

-

-

d

0

e Q345

A

3

3

32

31

5

5

B

4

3

C

5

5

3

28

0

5

275

5

47

47

3

35

33

3

31

B

9

7

0

0

3

0

C

0

0

-

4

-

2

1

1

1

1

0

0

7

0

～

5

0 9

9

8

7

～

～

0

～

600

0

2

2

2

1

1

2

63

63

～

63

～

450

1 0

0

9

8

17

6

0

0

6

0

6

～

3

0

600

0

0 2

1

1

1

-

-

0 9

9

8

-

-

-

-

-

-

5 3

450

5

E

A

47

6

D

Q390

4

-

-

49

49

4

49

470

0

0

9

0

～

～

～

0

～

620

D

65

65

～

65

E

0

0

6

0

0

-

-

5 0 Q420

A

4

4

38

36

3

34

B

2

0

0

0

6

0

C

0

0

-

-

-

52

52

5

52

500

0

0

2

0

～

～

～

0

～

650

D

68

68

～

68

E

0

0

6

0

0

-

-

1

1

1

1

9 8

8

8

1

1

1

1

7 6

6

6

1

1

1

-

7 7

7

8 0 Q460

C

4

4

42

40

4

38

D

6

4

0

0

0

0

E

0

0

-

-

-

0

55

55

5

55

530

0

0

5

0

～

～

～

0

～

700

72

72

～

72

0

0

7

0

-

-

2 0 Q500

C

5

4

47

45

4

D

0

8

0

0

E

0

0

-

-

-

-

61

60

5

54

4

0

0

9

0

0

～

～

0

～

77

76

～

73

0

0

7

0

5 0 8

-

-

-

GB/T 1591—2008 Q550

C

5

5

52

50

4

D

5

3

0

0

E

0

0

-

-

-

-

67

62

6

59

9

0

0

0

0

0

～

～

0

～

83

81

～

78

0

0

7

0

-

-

-

1

1

1

6 6

6

1

1

1

5 5

5

1

1

1

4 4

4

-

-

-

-

-

-

-

-

9 0 Q620

C

6

6

59

57

0

0

D

2

0

E

0

0

-

-

-

-

-

71

69

6

0

0

7

～

～

0

88

88

～

0

0

8

-

-

-

-

6 0 Q690

C

6

6

66

64

D

9

7

0

0

E

0

0

-

-

-

-

-

77

75

7

0

0

3

～

～

0

94

92

～

0

0

9

-

-

-

-

0 0 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.

1.6.4.2 　 Charpy V-notch impact test The test temperature and absorbed energy values of Charpy V-notch impact test of steels shall comply with the specified values of table 7. 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. 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

9

GB/T 1591—2008 may be lower than the minimum average value specified and not more than one may be lower than 70 % of this value. 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

Test temperature/℃

grade

Q345

20

C

0

D

-20

E

-40

B

20

C

0

D

-20

E

-40

B

20

C

0

D

-20

E

-40

C

0

D

-20

E

-40

Q500 、 Q550

C

、 Q620 、 Q69 0

Q420

Q460

a

a

KV2 /J

Nominal thickness( diameter, border)/mm

B

Q390

Minimum absorbed energy

12～ 150

＞ 150 ～ 250

＞ 250 ～ 400

34

27

-

27

34

-

-

34

-

-

34

-

-

0

55

-

-

D

-20

47

E

-40

31

The impact test pieces shall be in the longitudinal direction.

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

10

＞ 16～ 100

GB/T 1591—2008 Q345

For flat steel products with their

Q390

widths not less than 600mm, the bend

Q420

test pieces shall be in the

Q460

transverse direction. For sections,

2a

3a

bars and flat steel products with their widths less than 600mm, the bend test pieces shall be in the longitudinal direction

Surface properties The surface condition of steel products shall be in accordance with the requirements specified in relevant documents. 1.6.5 　 Specific requirement 1.6.5.1 　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. 1.6.5.2 　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. 1.6.5.3 　According to the agreement between the purchaser and the manufacturer, other tests may be carried out. 1.7 　 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.

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

1/furnace

GB/T 20066

GB/T 223 、 GB/T 4336 、 GB/T 20125

( ladle analysis ) 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

3/lot

GB/T 5313

GB/T 5313

Each sheet or

Relevant document for

By agreement

piece

non-destructive

reduction of area 6

Non-destructive testing

testing 11

GB/T 1591—2008 7

Surface condition

Each sheet or

-

piece

By visual inspection or measuring equipment

8

Dimensions, shape

Each sheet or piece

-

By applicable measuring equipment

1.8 　 Inspection 1.8.1 　 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. 1.8.2 　 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. 1.8.3 　 Retest and acceptance criteria 1.8.3.1 　 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. 1.8.3.2 　 Retest and acceptance criteria for other test

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_________________________________ GB/T 1591—2008 The retest and acceptance criteria for other test of steel products shall be in accordance with GB/T 17505. 1.8.4 　 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. 1.9 　 Packaging, marking, certification The packaging,marking and certification for steel procucts ahall be in accordance with GB/T 247 or GB/T 2101.

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