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GB/T 11251-2009 (GB/T11251-2009)

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GB/T 11251-2009: PDF in English (GBT 11251-2009)
GB/T 11251-2009
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.50
H 46
Replacing GB/T 11251-1989
Hot-rolled alloy structural steel plates
ISSUED ON. OCTOBER 30, 2009
IMPLEMENTED ON. MAY 01, 2010
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Order content ... 7 
4 Size, shape and allowable deviation ... 8 
5 Technical requirements ... 8 
6 Test methods ... 11 
7 Inspection rules ... 12 
8 Packaging, marking and quality certificate ... 13 
Hot-rolled alloy structural steel plates
1 Scope
This standard specifies the order content, size, shape and allowable deviation,
technical requirements, test methods, inspection rules, packaging, marking and
quality certificate of hot-rolled alloy structural steel plates.
This standard is applicable to hot-rolled alloy structural steel plates with a
thickness greater than 4 mm ~ 30 mm.
2 Normative references
The provisions in following documents become the provisions of this standard
through reference in this standard. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this standard;
however, parties who reach an agreement based on this standard are
encouraged to study if the latest versions of these documents are applicable.
For undated references, the latest edition of the referenced document applies.
GB/T 222 Permissible tolerances for chemical composition of steel products
GB/T 223.3 Methods for chemical analysis of steels and alloys -
Determination of phosphorus content by diantipyryl methane
phosphomolybdate gravimetric method
GB/T 223.4 Alloyed steel - Determination of manganese content -
Potentiometric or visual titration method
GB/T 223.5 Steel and iron - Determination of acid-soluble silicon and total
silicon content - Reduced molybdosilicate spectrophotometric method
GB/T 223.8 Methods for chemical analysis of iron, steel and alloy - The
sodium fluoride separation-EDTA titration method for the determination of
aluminium content
GB/T 223.9 Iron steel and alloy - Determination of aluminum content - Chrom
azurol S photometric method
GB/T 223.11 Iron, steel and alloy - Determination of chromium content -
Visual titration or potentiometric titration 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 223.13 Methods for chemical analysis of iron, steel and alloy - The
ammonium ferrous sulfate titration method for the determination of vanadium
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 223.17 Methods for chemical analysis of steels and alloy - The
diantipyrylmethane photometric method for the determination of titanium
content
GB/T 223.18 Methods for chemical analysis of iron, steel and alloy - The
sodium thiosulfate separation iodimetric method for the determination of
copper content
GB/T 223.19 Methods for chemical analysis of steels and alloys - The 2,9-
dimethyl-1,10-phenanthroline-trichloromethane extraction
spectrophotometric 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 223.25 Methods for chemical analysis of iron, steel and alloy - The
dimethylglyoxime gravimetric method for the determination of nickel content
GB/T 223.26 Iron, steel and alloy - Determination of molybdenum content -
The thiocyanate spectrophotometric method
GB/T 223.43 Iron steel and alloy - Determination of tungsten content -
Gravimetryc method and spectrophotometric method
GB/T 223.49 Methods for chemical analysis of iron, steel and alloy -
Extraction separation-chlorophosphonazo mA spectrophotometric method
for the determination of the total rare earth content
GB/T 223.54 Methods for chemical analysis of iron, steel and alloy - The
flame atomic absorption spectrophotometry for the determination of nickel
content
GB/T 223.58 Methods for chemical analysis of iron, steel and alloy - The
distillation-curcumin photometric method
GB/T 223.76 Methods for chemical analysis of iron, steel and alloy - The
flame atomic absorption spectrometric method for the determination of
vanadium content
GB/T 224 Determination of depth of decarburization of steels
GB/T 226 Test method for macrostructure and defect of steel by etching
(GB/T 226-1991, neq ISO 4969.1980)
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 231.1 Metallic materials - Brinell hardness test - Part 1. Test method
(GB/T 231.1-2002, eqv ISO 6506-1.1999)
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 709-2006 Dimension, shape, weight and tolerances for hot rolled
sheets and strips
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 3077 Alloy structure steels
GB/T 13298 Metal - Inspection method of microstructure
GB/T 13299 Steel - Determination of microstructure
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)
3 Order content
Contracts or orders placed in accordance with this standard shall include the
25CrMnSiA and 30CrMnSiA may be subjected to the determination of
specimen’s mechanical properties at the quenching and tempering status. The
heat treatment system and test results of the specimen shall comply with the
requirements of Table 2. Steel plates with a thickness of not more than 12 mm
can be sampled and inspected on the plate blank.
Table 2
Designation
Heat treatment system of specimen Mechanical properties
Quenching Tempering Tensile strength, Rm/(N/mm2)
Elongation at
fracture, A/%
Energy
absorption at
impact, KU2/J
Temperature
/ °C Coolant
Temperature
/ °C Coolant Not less than
25CrMnSiA 850 ~ 890 Oil 450 ~ 550 Water, oil 980 10 39
30CrMnSiA 860 ~ 900 Oil 470 ~ 570 Oil 1080 10 39
5.4 For steel plates used for stamping (specified in the contract) with a thickness
of not more than 10 mm, it shall be subjected to the bending test in a cold status.
The specimen is bent to 180°, the bend diameter is d = 2α (α is the thickness
of the specimen). The outer surface of the specimen at the bend shall be free
of cracks or delamination.
5.5 Macrostructure
Acid-leached macrostructures of steel plates or billets shall not have visible
shrinkage cavities, cracks and inclusions.
5.6 Decarbonization
5.6.1 According to the requirements of the purchaser, it may inspect the depth
of the decarburization layer of the steel plate. For the steel plate with a thickness
of not more than 20 mm, the depth of the full decarburization layer (ferrite) at
each side shall not exceed 2.5% of the nominal thickness of the steel plate, the
sum of the two sides shall not exceed 4.0%; for the steel plate with a thickness
greater than 20 mm, it shall not exceed 2.0% of nominal thickness of the steel
plate at each side.
5.6.2 After consultation between the supplier and the purchaser, and indicated
in the contract, it may supply the steel plate with a total thickness of
decarburization layer (ferrite + transition layer) at each side of not more than
5.0% of the nominal thickness.
5.7 Microstructure
According to the requirements of the purchaser, the steel plates 25CrMnSiA
and 30CrMnSiA can be subjected to inspection of band structure, the results
shall not exceed grade 3. After consultation between the supplier and the
Table 4 (continued)
No. Inspection item Sampling quantity/piece Sampling location Test methods
4 Impact 2 GB/T 2975 7.3.2, 7.3.3 GB/T 229
5 Bending 1 Any one steel plate or roll GB/T 232
6 Macrostructure 2
Different steel plates or
7.3.2, 7.3.3 or on the
steel ingot close to the
box-hat end
GB/T 226
7 Decarburization 2 7.3.2, 7.3.3 GB/T 224
8 Microstructure 2 7.3.2, 7.3.3 GB/T 13298 GB/T 13299
9 Size Piece by piece Whole steel plate Micrometer, template
10 Surface Piece by piece Whole steel plate Visual inspection
7 Inspection rules
7.1 Inspection and acceptance
7.1.1 The exit-factory inspection and acceptance of the steel plate shall be
carried out by the supplier’s quality technical supervision department.
7.1.2 The supplier must ensure that the steel plate delivered meets the
requirements of this standard or contract. If necessary, the purchaser has the
right to inspect and accept any inspection items as specified in this standard or
contract.
7.2 Group-batch rules
The steel plates shall be inspected and accepted by batches. Each batch shall
consist of steel plates of the same furnace number, the same thickness, the
same group, the same heat treatment furnace (the same heat treatment system
for the continuous furnace).
7.3 Sampling quantity and sampling locations
7.3.1 The sampling quantity and sampling locations of each batch of steel plates
shall comply with the requirements of Table 4.
7.3.2 For the steel plate heat-treated in palletization, take one piece of steel
plate for inspection purposes from the upper part and lower part, respectively,
of each pallet from each batch; for the steel plates heat-treated in continuous
furnace, take one piece of steel plate for inspection purposes from the starting
and tail, respectively, of each heat treatment. Take 1 specimen from each piece
......
 
(Above excerpt was released on 2018-10-27, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT11251-2009