GB/T 699-2015 Quality Carbon Structure Steels

2021-12-08
GB/T 699-2015
Quality Carbon Structure Steels
 
 
1 Scope
This standard specifies classification and code, order contents, size, shape and weight,technical requirements, test methods, inspection rules as well as packaging, marking andquality certificate of quality carbon structure steel bars.
 
This standard is applicable to the hot-rolled and forged quality carbon structure steel bars with nominal diameter or thickness not greater than 250mm. The hot-rolled and forged quality carbon structure steelbars with the nominal diameter or thickness greater than 250mm may also be provided basing on the agreement of both the Supplier and the Purchaser.The grade and chemical composition specified in this standard are also applicable to steel ingot, steel billet, steel products with other sections and their products.
 
 
 
 
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only dated editions apply. For undated references, the lastest editions (including any amendments) apply.
GB/T 222 Permissible Deviations 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 223.11 Iron Steel and Alloy - Determination of Chromium Content - Visual Titration or Potentiometric Titration Method
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 223.59 Iron Steel and Alloy - Determination of Phosphorus Content -Bismuth Phosphomolybdate Blue Spectrophotometric Method and Antimony Phosphomolybdate Blue Spectrophotometric Method
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 223.79 Iron and Steel - Determination of Multi-element Contents - X-ray Fluorescence Spectrometry (Routine Method)
GB/T 223.81 Iron Steel and Alloy - Determination of Total Aluminum and Total Boron Contents - Microwave Digestion-Inductively Coupled Plasma Mass Spectrometric Method
GB/T 223.85 Steel and Iron - Determination of Sulfur Content - Infrared Absorption Method after Combustion in an Induction Furnace
GB/T 223.86 Steel and Iron - Determination of Total Carbon Content - Infrared Absorption Method after Combustion in an Induction Furnace
GB/T 224 Determination of Depth of Decarburization of Steel
GB/T 225 Steel - Hardenability Test by End Quenching (Jominy Test)
GB/T 226 Etch Test for Macrostructure and Defect of Steels
GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature
GB/T 229 Metallic Materials - Charpy Pendulum Impact Test Method
GB/T 231.1 Metallic Materials - Brinell Hardness Test - Part 1: Test Method
GB/T 702 Hot-Rolled Round and Square Steel Bars - Dimension, Shape,Weight and Tolerance
GB/T 908 Forged Bars - Dimension, Shape, Weight and Tolerance
GB/T 1979 Standard Diagrams for Macrostructure and Defect of Structural Steels
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 4162 Forged and Rolled Steel Bars - Method for Ultrasonic Testing
GB/T 4336 Standard Test Method for Spark Discharge Atomic Emission
Spectrometric Analysis of Carbon and Low-alloy Steel (Routine
Method)
GB/T 6394 Metal - Methods for Estimating the Average Grain Size
GB/T 6402 Steel Forgings - Method for Ultrasonic Testing
GB/T 7736 Ultrasonic Inspecting Method for Macro-structure and Imperfection of Steel
GB/T 8170-2008 Rules of Rounding Off for Numerical Values & Expression and Judgment of Limiting Values
GB/T 10561 Steel - Determination of Content of Nonmetallic Inclusions -Micrographic Method using Standards Diagrams
GB/T 11261 Steel and Iron - Determination of Oxygen Content - The Pulse Heating Inert Gas Fusion-Infra-red Absorption Method
GB/T 13298 Metal - Inspection Method of Microstructure
GB/T 13299 Steel - Determination of Microstructure
GB/T 15711 Steel Products - Method for Ecth Test of Tower Sample
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 20124 Steel and Iron - Determination of Nitrogen Content - Thermal Conductimetric Method after Fusion in a Current of Inert Gas
(Routine Method)
GB/T 20125 Low-alloy Steel - Determination of Multi-Element Contents -Inductively Coupled Plasma Atomic Emission Spectrometric Method
GB/T 21834 Medium and Low Alloy Steel - Determination of the Distribution of Multi-element Contents - Original Position Statistic Distribution Analysis Method
GB/T 28300 Surface Quality Classes for Hot-rolled Bars and Rods Technical Delivery Conditions
YB/T 4306 Steel and Iron - Determination of Nitrogen Content-Thermal Conductimetric Method after Fusion in a Current of Inert Gas
YB/T 5293 Metallic Materials - Forging Test
 
 
 
3 Classification and Code
3.1 Steel bars are classified into the following two categories in accordance with application and machining method:
a) Steel used for press working       UP;
1) Steel used for hot working       UHP;
2) Steel used for upsetting        UF;
3) Steel used for cold-drawn blank      UCD.
b) Steel used for cut work           UC.
3.2 Steel bars are divided into the following five categories according to surface type:
a) Press working surface       SPP;
b) Acid washing          SA;
c) Shot (sand) blasting       SS;
d) Peeling      SF;
e) Polishing      SP.
 
 

4 Order Contents
The order contract or order according to this standard shall include the following contents:
a) Standard number;
b) Product name;
c) Designation or uniform numeric code;
d) Delivery weight (or quantity);
e) Size, shape and their permissible deviation (see Chapter 5);
f) Application and machining method (according to steel used for cut work if not indicated);
g) Delivery in heat treatment state or special surface state (see 6.3.2 and 6.3.3 if required);
h) Impact test (see 6.4.2 if required);
i) Upset (see 6.5 if required);
j) Decarburized layer (see 6.7 if required);
k) Special requirements (see 6.9 if required)
 
 
 
5 Size, Shape and Weight
5.1 The size, shape, weight and permissible deviation of hot rolled steel bars shall meet those specified in GB/T 702 and the specific requirements shall be noted in the Contract.
5.2 The size, shape, weight and permissible deviation of forged steel bars shall meet those specified in GB/T 908 and the specific requirements shall be noted in the Contract.
 
 
 
6 Technical Requirements
6.1 Designation and chemical composition
6.1.1 The designation, uniform numeric code and chemical composition (smelting analysis) of steel shall be in accordance with those specified in Table 1.
 
Table 1 Designation, Uniform Numeric Code and Chemical Composition of Steel
 
No. Uniform
numeric
code		 Designation Chemical composition (mass fraction)/%
C
 		 Si
 		 Mn
 		 P S Cr Ni Cu a
≤    
1 U20082 08 b 0.05~0.11 0.17~0.37 0.35~0.65 0.035 0.035 0.10 0.30 0.25
2 U20102 10 0.07~0.1 3 0.17~0.37 0.35~0.65 0.035 0.035 0.15 0.30 0.25
3 U20152 15 0.12~0.18 0.17~0.37 0.35~0.65 0.035 0.035 0.25 0.30 0.25
4 U20202 20 0.17~0.23 0.17~0.37 0.35~0.65 0.035 0.035 0.25 0.30 0.25
5 U20252 25 0.22~0.29 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
6 U20302 30 0.27~0.34 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
7 U20352 35 0.32~0.39 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
8 U20402 40 0.37~0.44 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
9 U20452 45 0.42~0.50 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
10 U20502 50 0.4 7~0.55 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
11 U20552 55 0.52~0.60 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
12 U20602 60 0.57~0.65 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
13 U20652 65 0.62~0.70 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
14 U20702 70 0.67~0.75 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
15 U20702 75 0.72~0.80 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
16 U20802 80 0.77~0.85 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
17 U20852 85 0.82~0.90 0.17~0.37 0.50~0.80 0.035 0.035 0.25 0.30 0.25
18 U21152 15Mn 0.12~0.18 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
19 U21202 20Mn 0.17~0.23 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
20 U21252 25Mn 0.22~0.29 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
21 U21302 30Mn 0.27~0.34 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
22 U21352 35Mn 0.32~0.39 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
23 U21402 40Mn 0.37~0.44 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
24 U21452 45Mn 0.42~0.50 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
25 U21502 50Mn 0.48~0.56 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
26 U21602 60Mn 0.57~0.65 0.17~0.37 0.70~1.00 0.035 0.035 0.25 0.30 0.25
27 U21652 65Mn 0.62~0.70 0.17~0.37 0.90~1.20 0.035 0.035 0.25 0.30 0.25
28 U21702 70Mn 0.67~0.75 0.17~0.37 0.90~1.20 0.035 0.035 0.25 0.30 0.25
Any element not specified in this table shall not be added without agreement of the users. Measures shall be taken to prevent steel scrap or other materials from bringing in element which influences performance of steels.
a  Copper content for steel used for hot press working shall not be greater than 0.20%;
b  For aluminium-deoxidized killed steel, there is no lower limit for carbon and manganese content, upper limit of manganese content is 0.45%, the silicon content is not greater than 0.03% and total aluminium content is 0.020%~0.070%, the designation is 08Al in such condition.
 
 
6.1.2 As for the steel smelted by the oxygen converter, the nitrogen content shall not be greater than 0.008%. The steel may not be analyzed when the Supplier can ensure it is qualified.
6.1.3 For 35~85 steels used for patenting steel wire, manganese content is 0.30%~0.60%,manganese content of 65Mn and 70 Mn is 0.70%~1.00%, chromium content is not greater than 0.10%, nickel content is not greater than 0.15% and copper content is not greater than 0.20%; the sulfur and phosphorus content shall also meet the standard requirements for the steel wire.
6.1.4 Permissible deviation for the chemical composition of steel bar (or blank) shall meet those specified in GB/T 222.
6.2 Smelting method
Unless it is specified in contract, the smelting method shall be selected by the manufacturer voluntarily.
 
6.3 Delivery state
6.3.1 Generally, steel bars are delivered in hot-rolled or forged state.
6.3.2 The delivery also may be in heat treatment (annealing, normalizing or high temperature tempering) state if required by the Purchaser and indicated in the Contract.
6.3.3 The delivery also may be in special surface state (acid washing, shot blasting, peeling or polishing) if required by the Purchaser and indicated in the Contract.
6.4 Mechanical performance
6.4.1 Determination of longitudinal tensile performance by sample blank made of normalized blank shall meet those specified in Table 2. The steel products may not be tested when the Supplier can guarantee the mechanical performance is qualified.
6.4.2 As required by the Purchaser, the determination of longitudinal impact absorbing energy of 25~50, 25Mn~50Mn steel bar by the sample made of the heat-treated (quenched +tempered) blank shall meet those specified in Table 2. The round steel with nominal diameter less than 16mm and the square steel with nominal thickness not greater than 12mm shall be not subjected to the impact test.
6.4.3 The hardness of steel bars used for cut work or blank for cold-drawing at delivery condition shall meet those specified in Table 2. The hardness of steels not subjected to heat treatment may not be tested if the Supplier is able to guarantee the quality. The hardness value of steel bars after high temperature tempering or normalizing, it may be determined through negotiation between the Supplier and the Purchaser.
6.4.4 As required by the Purchaser, tensile strength of 25~60 steel bars is permitted to be 20MPa lower than value specified in Table 2, but its percentage elongation after fracture is improved by 2% (absolute value) at the same time.
 
 
Table 2 Mechanical Performance
 
Designation Blank
sample
size a
mm		 Recommended heat treatment
system 		 Mechanical performance     Delivery
hardness HBW 
Normalizing Quenching Tempering Tensile
strength
R m
MPa		 Lower
yield
strength
R eL d
MPa		 Percentage
elongation
after
fracture A
%		 Impact
absorbed
energy
KU 2
J		 Impact
absorbed
energy
KU 2
J		 Non
heat
treated
steel		 Annealed
steel
Heating temperature/℃   ≥ ≥
08 25 930 — — 325 195 33 60 — 131 —
10 25 930 — — 335 205 31 55 — 137 —
15 25 920 — — 375 225 27 55 — 143 —
20 25 910 — — 410 245 25 55 — 156 —
25 25 900 870 600 450 275 23 50 71 i70 —
30 25 880 860 600 490 295 21 50 63 179 —
35 25 870 850 600 530 315 20 45 55 197 —
40 25 860 840 600 570 335 19 45 47 217 187
45 25 850 840 600 600 355 16 40 39 229 197
50 25 830 830 600 630 375 14 40 31 241 207
55 25 820 — — 645 380 13 35 — 255 217
60 25 810 — — 675 400 12 35 — 255 229
65 25 810 — — 695 410 10 30 — 255 229
70 25 790 — — 715 420 9 30 — 269 229
75 Sample — 820 480 1 080 880 7 30 — 285 241
80 Sample — 820 480 1 080 930 6 30 — 285 241
85 Sample — 820 480 1130 980 6 30 — 302 255
15Mn 25 920 — — 410 245 26 55 — 163 —
20Mn 25 910 — — 450 275 24 50 — 197 —
25Mn 25 900 870 600 490 295 22 50 71 207 —
30Mn 25 880 860 600 540 315 20 45 63 217 187
35Mn 25 870 850 600 560 335 18 45 55 229 197
40Mn 25 860 840 600 590 355 17 45 47 229 207
45Mn 25 850 840 600 620 375 15 40 39 241 217
50Mn 25 830 830 600 645 390 13 40 31 255 217
60Mn 25 810 — — 690 410 11 35 — 269 229
65Mn 25 830 — — 735 430 9 30 — 285 229
70Mn 25 790 — — 785 450 8 30 — 285 229
Mechanical performance in the table is applicable to steel bars with nominal diameter or thickness not greater than 80mm.
As for steel bars with nominal diameter or thickness greater than 80mm~250mm, the percentage elongation after fracture and percentage reduction of area are permitted to be 2% (absolute value) and 5% (absolute value) lower than those specified in this table respectively.
Steel bars with nominal diameter or thickness greater than 120mm~250mm are permitted to be forged (rolled) into 70mm~80mm samples and subjected to sampling inspection, the result shall meet those specified in this table.
a  Where the size of steel bar is less than that of sample blank, steel bar in original size are subjected to heat treatment.
b  As for sample with working allowance, the performance is that in quenching + tempering state.
c Permissible adjustment range of heat treatment temperature: ±30℃ for normalizing, ±20℃ for quenching and ±50℃ for tempering; recommended holding time: at least 30min for normalizing, air cooling; at least 30min for quenching, oil cooling for 75, 80 and 85 steels and water cooling for other steel bars; at least 1h for 600℃ tempering.
d  In case of inapparent yield phenomenon, it may be replaced by specified plastic elongation strength R p0.2 .
 
 
 
 
6.5 Upsetting
6.5.1 For steel used for upsetting, hot upsetting or cold upsetting shall be noted in the Contract. The height of sample after hot upsetting and cold upsetting test shall be respectively 1/3 and 1/2 of the height of former sample. Sample surface after upsetting shall be free from visible crack.
6.5.2 The hot upsetting steel with nominal diameter greater than 80mm or the cold upsetting steel with nominal diameter greater than 30mm may not be tested if the Supplier is able to guarantee the upset test is qualified.
6.6 Macrostructure
6.6.1 The acid leaching macrostructure test plate of steel bar cross section shall be free from visible shrinkage cavity, bubble, crack, inclusion, skull patch or flake. As for steel bar for cut work, imperfections such as subsurface inclusion or subsurface bubble with a depth less than or equal to those specified in Table 6 is allowed.
6.6.2 The acid leaching macrostructure of steel bar shall meet those specified in Table 3.
 
Table 3 Qualification Grade of Macrostructure
 
 
General looseness Central looseness Ingot shape segregation Center segregation a
Grade, ≤   
 
2.5 2.5 2.5 2.5
a Only for continuously cast steel bar.   
 
 
6.6.3 If the supplier could guarantee that the macroscopic test is qualified, ultrasonic testing method specified in GB/T 7736 or other nondestructive inspection methods may be used to replace acid leaching macroscopic test.
6.7 Decarburized layer
The group shall be indicated in the Contract as required by the Purchaser; in case of inspection of decarburized layer of steel bar with nominal carbon content lower limit greater than 0.30%, total decarburized layer depth (ferrite + transition layer) of each edge shall meet those specified in Table 4.
 
Table 4 Permissible Depth of Total Decarburized Layer In: mm
 
Group Permissible total decarburized layer depth, ≤
Group I 1.0%D
Group II 1.5%D
Note: D is the nominal diameter or thickness of steel bars. 
 
 
6.8 Surface quality
6.8.1 The surface of steel bars for press working shall be free from visible cracks, scars,folds and inclusions. The above-mentioned defects must be cleaned up if they exist, the cleaned depth shall be calculated from the actual dimension of steels and shall be in accordance with those specified in Table 5, the cleaned width shall not be less than 5 times of depth. For steels with nominal diameter or side length greater than 140mm, the maximum cleaned depth at the same section shall not be more than two positions. The individual tiny
scratches, impressions and pockmarks not exceeding the half of the dimensional tolerance calculated from the actual dimension and the crackles with depth not exceeding 0.2mm are allowed to exist.
 
 
 
Table 5 Permissible Defect of Steel for Pressure Work Bar      In: mm
 
Nominal diameter or thickness Allowable defect removal depth
<80 1/2 of the nominal dimensional tolerance of steels
≥80~140 Nominal size tolerance of steel bar
>140~200 5% of steel bar nominal size
>200 6% of steel bar nominal dimension
 
 
6.8.2 As for the steel bar for cut work, the local defects not exceeding those specified in Table 6 calculated according to the steel nominal dimension are allowed to exist on surface.
 
Table 6 Permissible Depth of Partial Imperfection for Steel for Cutting Work            In: m
 
Nominal diameter or thickness Permissible depth of partial imperfection
<100 Negative deviation of the nominal size of steel bar
≥100 Nominal size tolerance of steel bar
 
 
6.8.3 The surface of steel bars delivered in shot blasting or peeling state shall be free from cracks, wrinkles, scars, inclusion and iron scale. The above-mentioned defects may be cleaned up if they exist, but the greatest cleaned depth shall ensure the minimum dimension of steel bars.
6.8.4 As required by the Purchaser, surface quality of hot rolled steel bars may meet those specified in GB/T 28300, specific quality level and acceptance quality limit AQL (maximum magnitude of defect) and inspection method is determined through negotiation between the Supplier and Purchaser.
 
 
 
6.9 Specific requirements
The steel bars with the following special requirements may be supplied through agreement between the Supplier and the Demander and indicated in the contract:
a) Reduce or broaden the chemical composition range for designations in Table 1;
b) Control sulfur content within the range of 0.015%~0.035%;
c) Analyze oxygen content or other residual elements;
d) Provide small size impact test value or V-notch impact test value;
e) Provide steel bar with requirement of hardenability characteristic;
f) Inspect grain size;
g) Inspect nonmetallic inclusion;
h) Inspect tower-shaped hair crack;
i) Inspect microstructure;
j) Ultrasonic testing;
k) Other.
 
 
 
 
7 Test Methods
See Table 7 for the inspection items and test methods of steel bars.

Table 7 Inspection Items, Sampling Quantity, Sampling Position and Test Methods of Steel Bars
 
No Inspection items  Sampling
quantity		 Sampling position Test methods
1 Chemical composition  1/furnace GB/T 20066 GB/T 223(see Chapter 2), GB/T
4336, GB/T 11261, GB/T
20123, GB/T 20124, GB/T
20125, GB/T 21834 and YB/T
4306
2 Tensile  2/batch Different steel bars, GB/T 2975 GB/T 228.1
3 Impact  1 group a /batch Different steel bars, GB/T 2975 GB/T 229
4 Brinell hardness  3/batch Different steel bars GB/T 231.1
5 Upsetting  2/batch Different steel bars YB/T 5293
6 Macrostructure Acid
etching test		 2/batch Die casting: different steel billets or steel bars
equivalent to ingot head
Continuous casting: different steel bars		 GB/T 226 and GB/T 1979
    Ultrasonic
testing		     GB/T 7736
7 Tower-shaped hair crack  2/batch Different steel bars GB/T 15711
8 Decarburized layer  2/batch Different steel bars GB/T 224 (Metallurgical
method)
9 Grain size  1/batch Any steel bar GB/T 6394
10 Nonmetallic inclusion  2/batch Different steel bars GB/T 10561
11 Microstructure  1/batch Different steel bars GB/T 13298 and GB/T 13299
12 End quench hardenability  1/batch Any steel bar, GB/T 225 GB/T 225
13 Ultrasonic testing  One by one Entire steel bar GB/T 4162 and GB/T 6402
14 Surface quality  One by one Entire steel bar Visual inspection or GB/T
28300
15 Size and shape  One by one Entire steel bar Caliper, micrometer, etc.
a A group: 2 for U-notch and 3 for V-notch.
 
 
 
 
8 Inspection Rules
8.1 Inspection and acceptance
8.1.1 The ex-factory inspection and acceptance of steel bars shall be carried out by the quality and technology supervision department of the Supplier.
8.1.2 The Supplier shall guarantee that the delivered steel bars meet those specified in this standard or the Contract, and if necessary, the Purchaser is entitled to carry out inspection and acceptance for any inspection item specified in this standard or the Contract.
8.2 Batching (grouping) rules
Steel bars shall be inspected and accepted according to batches and each batch is composed of steel bars of same designation, furnace No., processing method, size, delivery state and heat treatment system (heat No.).
8.3 Sampling quantity and sampling position
Sampling quantity and sampling position of each batch of steel bars shall meet those specified in Table 7.
8.4 Reinspection and judgement rules
8.4.1 The reinspection and judgment rules of steel bars shall be in accordance with those specified in GB/T 17505.
8.4.2 If the Supplier is able to guarantee that the steel bars are qualified, as for the inspection results on macrostructure, mechanical performance and nonmetallic inclusions of steel bars or steel billets of the same furnace No., it is allowed to use blank as materials and use the large as the small.
8.4.3 The test result of steel bars shall be rounded off to the number with digits consistent with that of specified value by rounding-off value comparison method, and the rounding off rules shall meet those specified in Chapter 3 of GB/T 8170-2008.
 
 
 
9 Packaging, Marking and Quality Certificate
The packaging, marking and quality certificate of steel bars shall meet those specified in GB/T 2101.
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