1 Scope
This standard specifies the scope, terms and definitions, ordering information, dimensions, shape, weight and tolerances, technical requirements, test methods, inspection rules, packing, marking and quality certificate of free-cutting structural steels.
This standard is applicable to such steels as bar steels, wire rods, steel wires, steel plates and steel strips used for mechanical machining and their chemical compositions are also applicable to ingots and billets as well as their products.
2 Normative References
The following normative documents contain provisions which, through reference in this text, constitute provisions of this national standard. For dated references, subsequent amendments to (excluding amending error in the text), or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest edition of the normative document is applicable. 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 223.3 Methods for Chemical Analysis of Iron, Steel and Alloy-The Diantipyrylmethane Phosphomolybdate Gravimetric Method for the Determination of Phosphorus Content
GB/T 223.11 Methods for Chemical Analysis of Iron, Steel and Alloy--The Ammonium Persulfate Oxidation Volumetric Method for the Determination of Chromium Content
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 223.19 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 223.29 Methods for Chemical Analysis of Iron, Steel and Alloy-The Xylenol Orange Photometric Method for Determination of Lead Content after Carrier Precipitation
GB/T 223.50 Methods for Chemical Analysis of Iron, Steel and Alloy-The Phenylfuorone-CTMAB Direct Photometric Method for the Determination of Tin Content
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 Methods for Chemical Analysis of Iron, Steel and Alloy; The Reduced Molybdoantimonyl Phosphoric Acid Photometric Method for the Determination of Phosphorus Content
GB/T 223.60 Methods for Chemical Analysis of Iron, Steel and Alloy The Perchloric Acid Dehydration Gravimetric Method for the Determination of Silicon Content
GB/T 223.61 Methods for Chemical Analysis of Iron, Steel and Alloy; The Ammonium Phosphomolybdate Volumetric Method for the Determination of Phosphorus Content
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 223.64 Methods for Chemical Analysis of Iron, Steel and Alloy; The Flame Atomic Absorption Spectrometric Method for the Determination of Manganese Content
GB/T 223.67 Iron Steel and Alloy-Determination of Sulfur Content-Methylene Blue Spectrophotometric 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 223.71 Methods for Chemical Analysis of Iron, Steel and Alloy; The Gravimetric Method after Combustion in the Pipe Furnace for the Determination of Carbon Content
GB/T 223.72 Iron Steel and Alloy-Determination of Sulfur Content-Gravimetric Method
GB/T 223.74 Methods for Chemical Analysis of Iron, Steel and Alloy - The Combustion Gravimetric/Gas-volumetric Method for the Determination of Combined Carbon Content
GB/T 223.77 Methods for Chemical Analysis of Iron, Steel and Alloy The Flame Atomic Absorption Spectrometric Method for the Determination of Calcium Content
GB/T 224 Determination of Depth of Decarburization of Steel
GB/T 226 Etch Test for Macrostructure and Defect of Steels
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 247 General Rule of Acceptance, Package, Mark and Certification for Steel Plates (Sheets) and Strips
GB/T 342 Dimension Shape Mass and Tolerance for Cold-drawn Round Square and Hexagonal Steel Wires
GB/T 702 Hot-rolled Steel Bars – Dimensions, Shape, Weight and Tolerances
GB/T 708 Dimension Shape Weight and Tolerance for Cold-rolled Steel Plates and Sheets
GB/T 709 Dimension Shape Weight and Tolerances for Hot-rolled Steel Plates and Sheets
GB/T 905 Dimension, Shape, Weight and Tolerance for Cold-drawn Round, Square and Hexagonal Steels
GB/T 908 Forged Bars - Dimensions Shape Weight and Tolerances
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 2103 General Provisions for Checking, Packing, Marking and Quality Certification of Steel Wire
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 3207 Bright Steel
GB/T 4336 Standard Test Method for Spark Discharge Atomic Emission Spectrometric Analysis of Carbon and Low-alloy Steel (Routine Method)
GB/T 10561 Steel Determination of Content of Nonmetallic Inclusions Micrographic Method Using Standards Diagrams
GB/T 14981 Dimensions, Shape, Mass and Tolerances for Hot-rolled Wire Rods
GB/T 15711 Steel Products-Method for Ecth Test of Tower Sample (GB/T 15711-1995, neq ISO 3673: 1976)
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 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
3 Terms and Definitions
The following term and definition is applicable to this standard.
3.1
Free-cutting structural steel
The structural steel of favorable machining performance by adding higher content of sulfur, lead, calcium and other free-cutting elements.
4 Classification
Steels shall be classified into the following two classes according to the different application and processing methods. The application and processing method for steel bars shall be noted in the contract and the unnoted one shall be supplied as steels for machining.
a) Steels for press working UP
b) Steel for machining UC
Contents
Foreword I
Introduction III
1 Scope
2 Normative References
3 Terms and Definitions
4 Classification
5 Ordering Information
6 Dimension, Shape, Weight and Tolerance
7 Technical Requirements
8 Test Methods
9 Inspection Rules
10 Packing, Marking and Quality Certificate
Appendix A (Informative) Reference Values for Mechanical Properties of Bar Steels and Wire Rods Made from Free-cutting Structural Steel
Appendix B (Informative) Comparison Table of Designations in this Standard with Foreign Designations
1 Scope
This standard specifies the scope, terms and definitions, ordering information, dimensions, shape, weight and tolerances, technical requirements, test methods, inspection rules, packing, marking and quality certificate of free-cutting structural steels.
This standard is applicable to such steels as bar steels, wire rods, steel wires, steel plates and steel strips used for mechanical machining and their chemical compositions are also applicable to ingots and billets as well as their products.
2 Normative References
The following normative documents contain provisions which, through reference in this text, constitute provisions of this national standard. For dated references, subsequent amendments to (excluding amending error in the text), or revisions of, any of these publications do not apply. However, all parties coming to an agreement according to this standard are encouraged to study whether the latest edition of the normative document is applicable. 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 223.3 Methods for Chemical Analysis of Iron, Steel and Alloy-The Diantipyrylmethane Phosphomolybdate Gravimetric Method for the Determination of Phosphorus Content
GB/T 223.11 Methods for Chemical Analysis of Iron, Steel and Alloy--The Ammonium Persulfate Oxidation Volumetric Method for the Determination of Chromium Content
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 223.19 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 223.29 Methods for Chemical Analysis of Iron, Steel and Alloy-The Xylenol Orange Photometric Method for Determination of Lead Content after Carrier Precipitation
GB/T 223.50 Methods for Chemical Analysis of Iron, Steel and Alloy-The Phenylfuorone-CTMAB Direct Photometric Method for the Determination of Tin Content
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 Methods for Chemical Analysis of Iron, Steel and Alloy; The Reduced Molybdoantimonyl Phosphoric Acid Photometric Method for the Determination of Phosphorus Content
GB/T 223.60 Methods for Chemical Analysis of Iron, Steel and Alloy The Perchloric Acid Dehydration Gravimetric Method for the Determination of Silicon Content
GB/T 223.61 Methods for Chemical Analysis of Iron, Steel and Alloy; The Ammonium Phosphomolybdate Volumetric Method for the Determination of Phosphorus Content
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 223.64 Methods for Chemical Analysis of Iron, Steel and Alloy; The Flame Atomic Absorption Spectrometric Method for the Determination of Manganese Content
GB/T 223.67 Iron Steel and Alloy-Determination of Sulfur Content-Methylene Blue Spectrophotometric 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 223.71 Methods for Chemical Analysis of Iron, Steel and Alloy; The Gravimetric Method after Combustion in the Pipe Furnace for the Determination of Carbon Content
GB/T 223.72 Iron Steel and Alloy-Determination of Sulfur Content-Gravimetric Method
GB/T 223.74 Methods for Chemical Analysis of Iron, Steel and Alloy - The Combustion Gravimetric/Gas-volumetric Method for the Determination of Combined Carbon Content
GB/T 223.77 Methods for Chemical Analysis of Iron, Steel and Alloy The Flame Atomic Absorption Spectrometric Method for the Determination of Calcium Content
GB/T 224 Determination of Depth of Decarburization of Steel
GB/T 226 Etch Test for Macrostructure and Defect of Steels
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 247 General Rule of Acceptance, Package, Mark and Certification for Steel Plates (Sheets) and Strips
GB/T 342 Dimension Shape Mass and Tolerance for Cold-drawn Round Square and Hexagonal Steel Wires
GB/T 702 Hot-rolled Steel Bars – Dimensions, Shape, Weight and Tolerances
GB/T 708 Dimension Shape Weight and Tolerance for Cold-rolled Steel Plates and Sheets
GB/T 709 Dimension Shape Weight and Tolerances for Hot-rolled Steel Plates and Sheets
GB/T 905 Dimension, Shape, Weight and Tolerance for Cold-drawn Round, Square and Hexagonal Steels
GB/T 908 Forged Bars - Dimensions Shape Weight and Tolerances
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 2103 General Provisions for Checking, Packing, Marking and Quality Certification of Steel Wire
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 3207 Bright Steel
GB/T 4336 Standard Test Method for Spark Discharge Atomic Emission Spectrometric Analysis of Carbon and Low-alloy Steel (Routine Method)
GB/T 10561 Steel Determination of Content of Nonmetallic Inclusions Micrographic Method Using Standards Diagrams
GB/T 14981 Dimensions, Shape, Mass and Tolerances for Hot-rolled Wire Rods
GB/T 15711 Steel Products-Method for Ecth Test of Tower Sample (GB/T 15711-1995, neq ISO 3673: 1976)
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 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
3 Terms and Definitions
The following term and definition is applicable to this standard.
3.1
Free-cutting structural steel
The structural steel of favorable machining performance by adding higher content of sulfur, lead, calcium and other free-cutting elements.
4 Classification
Steels shall be classified into the following two classes according to the different application and processing methods. The application and processing method for steel bars shall be noted in the contract and the unnoted one shall be supplied as steels for machining.
a) Steels for press working UP
b) Steel for machining UC
Contents of GB/T 8731-2008
Contents
Foreword I
Introduction III
1 Scope
2 Normative References
3 Terms and Definitions
4 Classification
5 Ordering Information
6 Dimension, Shape, Weight and Tolerance
7 Technical Requirements
8 Test Methods
9 Inspection Rules
10 Packing, Marking and Quality Certificate
Appendix A (Informative) Reference Values for Mechanical Properties of Bar Steels and Wire Rods Made from Free-cutting Structural Steel
Appendix B (Informative) Comparison Table of Designations in this Standard with Foreign Designations
