CB/T 773-1998 in English

Technical requirements for structure steel forging

1 Scope

This standard specifies the requirements of structure steel forgings for ships (hereinafter referred to as “forgings”), test methods, inspection rules, marks and quality certificates.

This standard is applicable to the manufacture and acceptance of carbon structural steel, carbon manganese structural steel, alloy structural steel, stainless acid-resistant steel, heat-resistant non-scaling steel and other forgings forged freely on marine hammers (including swage forgings).

2 Normative references

The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. At the time of publication, all editions listed were valid. All normative references used are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the latest editions of the normative standards indicated below.

GB 222-84 Method of sampling steel for determination of chemical composition and permissible variations for product analysis
GB 223.5-88 Methods for chemical analysis of iron, steel and alloy - oxalic acid - Oxalic acid - ferrous sulfate silicon and molybdenum blue photometric method for the determination of silicon
GB/T 223.12-91 Methods for chemical analysis of iron, steel and alloy - The sodium carbonate separation-diphenyl carbazide photometric method for the determination of chromium content
GB 223.26-89 Methods for chemical analysis of iron, steel and alloy - The thiocyanate direct photometric method for the determination of molybdenum content
GB 223.53-87 Methods for chemical analysis of iron, steel and alloy - The flame atomic absorption spectrophotometric method for the determination of copper content
GB 223.54-87 Methods for chemical analysis of iron, steel and alloy - The flame atomic absorption spectrophotometric method for the determination of nickel content
GB 223.59-87 Methods for chemical analysis of iron, steel and alloy- The reduced molybdoantimonyl phosphoric acid photometric method for the determination of phosphorus content

GB 223.63-88 Methods for chemical analysis of iron, steel and alloy - The sodium (potassium) periodate photometric method for the determination of manganese content
GB 223.68-89 Methods for chemical analysis of iron, steel and alloy - The combustion potassium iodate volumetric method for the determination of sulfur content
GB 223.69-89 Methods for chemical analysis of iron, steel and alloy - The gas- volumetric method after combustion for the determination of carbon content
GB 228-87 Metallic materials - Tensile testing
GB/T 229-1994 Metallic Materials - Charpy Notch Impact Test
GB 231-84 Metallic materials - Brinell hardness test
GB 699-88 Quality carbon structure steel - Technical requirements
GB 1220-92 Stainless steel bars
GB 1221-92 Heat-resisting steel bars
GB 3077-88 Alloy structure steel - Technical requirements

3 Requirements

3.1 Manufacture

3.1.1 Steel for forging shall be made of killed steel.

3.1.2 Steel ingots and rolled products used in forging shall have smelting furnace numbers and qualified chemical composition. The purchased billet shall also be accompanied by a certificate of mechanical properties. Other relevant billet acceptance requirements beyond those specified in this standard shall be negotiated by the supplier and the purchaser.

3.1.3 Ingots or billets shall have no slag inclusion, gas hole, scab, crack, fold, overburning and other defects before forging. All defects shall be cleaned before forging, and inspected for qualification by the inspection department before putting into use.

3.1.4 The ingot casting head and bottom shall be cut off.

3.1.5 The forging process shall be determined by the supplier.

3.2 Chemical composition

3.2.1 The chemical composition of forgings for hull structures shall be in accordance with those specified in Table 1.

Foreword i
1 Scope
2 Normative references
3 Requirements
4 Test methods
5 Inspection rules
6 Marking and quality certificate
Annex A (Normative) Strength grade of carbon steel and carbon manganese steel forgings
Annex B (Normative) Strength grade of alloy steel forgings