GB/T 33084-2016Heavy alloy structural steel forgings - Technical specification (English PDF)

1 Scope

China's national technical specification for heavy alloy structural steel forgings - the companion to GB/T 33083 and the more demanding of the pair, covering the large forgings made from alloy rather than plain carbon steel: the turbine and generator rotors, the heavy shafts, the press columns, the mill rolls and the pressure-retaining pieces where the section is too great, or the duty too severe, for a carbon steel to develop the properties required through its thickness. The standard specifies the ordering requirements, the manufacturing process, the technical requirements, the inspection rules and test methods, the acceptance and quality certificate, and the marking and packaging of alloy structural steel forgings for general use in mechanical products, and it applies to their ordering, manufacture and inspection. The reason alloy steel is used at all in this size is hardenability: on a heavy section a plain carbon steel simply cannot be cooled fast enough at the centre to transform properly, so the properties fall away from the surface inwards, and the alloying elements are added to shift that limit. Everything else in the standard follows: the tighter control of the chemical composition, the specification of the forging reduction and of the heat treatment on which the through-thickness properties depend, the strictly limited conditions for repair welding, the mechanical properties tabulated by grade and by section size rather than by grade alone, the hardness, and the non-destructive testing which on these pieces is the only means of knowing what is at the axis. The inspection clause again fixes where the test specimens are taken from each form of forging, and sets the retest and re-heat treatment provisions, before the acceptance, the quality certificate and the marking and packaging. Issued on 13 October 2016 and in force since 1 May 2017.

This Standard specifies the ordering requirements, manufacturing process, technical requirements, inspection rules and test methods, acceptance and quality certificates, marking and packaging of alloy structural steel forgings. This Standard applies to the ordering, manufacture and inspection of heavy alloy structural steel forgings for general purposes.

2 Normative References

The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this document.

GB/T 223 (all parts) Methods for Chemical Analysis of Iron, Steel and Alloy

GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Method of Test at Room Temperature ( GB/T 228.1-2010, ISO 6892-1:2009, MOD)

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- 2009, ISO 6506-1:2005, MOD)

3 Ordering Requirements

3.1 The purchaser shall specify the name, grade, material designation, delivery status and supply quantity of the forgings in the ordering contract.

3.2 The purchaser shall provide the ordering drawing.

3.3 When the purchaser has supplementary requirements, it shall be agreed upon by both parties.

4 Manufacturing Process

4.1 Smelting Steel for forgings shall be smelted by alkaline electric furnace. With the consent of the purchaser, other methods to ensure quality can also be used for smelting.

4.2 Forging Forgings shall be forged from ingots or billets. There shall be enough removal at both ends of the ingot to ensure that the forging body has no shrinkage cavity and serious segregation. Forgings shall be forged on forging equipment with sufficient capacity to ensure forging penetration and uniform structure. Forgings allow multiple length forging. Forgings shall be cooled slowly after forging to prevent cracking.

4.3 Heat treatment Forgings shall be cooled slowly by tempering at high temperature or normalizing and tempering or by other means to improve the structure and machinability. According to the material designation and strength grade of the forging, normalizing and tempering or quenching and tempering heat treatment process can be used. Forgings allow multiple length heat treatment.

7 Acceptance and Quality Certificate

7.1 The purchaser has the right to select certain test items of the forgings for acceptance. During the acceptance inspection or subsequent processing or inspection, the purchaser shall notify the supplier in time when it is found that the forging does not meet the supplementary technical requirements specified in this Standard and the ordering contract. the two parties shall negotiate a settlement.

7.2 The supplier shall provide the purchaser with a quality certificate, which shall at least include the following contents:

a) Contract number;

b) Forging drawing number;

c) The used standard number and material designation;

d) Smelting method, melting furnace number and forging identification number;

e) Chemical analysis report;

f) Mechanical properties test report;

g) Other inspections and supplementary inspection reports required by the purchaser;