GB/T 40883-2021Microalloyed steel forgings—General specification (English PDF)

3.1 Microalloyed steel forgings

The forgings that use micro-alloyed steel, through the forging process control and post-forging cooling process control, to meet the requirements of mechanical properties.

4.1 General requirements

4.1.1 Materials

4.1.7.2

When the supplier and the purchaser reach an agreement and the forgings are allowed to only meet the hardness requirements, the hardness level can be marked with "H", such as "60H", "80H", etc.

4.2 Other requirements

4.2.1 Ordering requirements

4.2.1.1 The order shall include. chemical composition, strength level of the product, test method and the number of mechanical property tests for each batch.

4.2.1.2 When the purchaser has a request, the ordering requirements can be determined through negotiation between the supplier and the purchaser.

4.2.1.3 When the purchaser has special requirements, it shall be indicated on the order according to Appendix A.

4.2.2 Process requirements

4.2.2.1 Appropriate hot working process and cooling method shall be selected for forgings to obtain the required mechanical properties.

4.2.2.2 When requested by the purchaser, the supplier shall provide the records of hot working parameters during the forging process, including but not limited to the following parameters. chemical composition of materials (including all microalloyed elements), blanking specifications of forgings, forging temperature and cooling time after forging.

4.2.2.3 After negotiation between the supplier and the buyer.

a) When the hardness of the forging is higher than the specified maximum value or the section elongation is lower than the specified minimum value, it shall be tempered and re-tested;

b) When the hardness of the forging is lower than the specified minimum value or the tensile strength and yield strength are lower than the specified minimum value; heat treatment shall be carried out.

4.2.2.4 For the unproduced billet after the first heating and the forging obtained by reheating and forging, its mechanical properties, depth of decarburization layer, hardness, grain size, etc. shall be negotiated with the purchaser, and can be used only after the purchaser agrees.

4.2.3 Production safety and environmental protection

The production safety and environmental protection requirements of forgings shall comply with the provisions of GB 13318.

5.1 Chemical composition of materials

Chemical composition analysis shall be carried out according to general methods such as GB/T 223 (all parts), GB/T 20123, GB/T 20124, GB/T 20125, etc., or take direct reading spectrometer detection.

5.2 Dimensions

Dimensional inspection should use general measuring tools, three-coordinate instruments or three-dimensional scanners for detection.

5.3 Forging streamline

Forging streamlines should be detected by hot acid etching or cold acid etching.

5.4 Surface quality

5.4.1 Appearance inspection may be used for visual inspection.

5.4.2 Surface defects such as folds and cracks should be detected by magnetic particle, and the magnetic particle detection method shall comply with the provisions of GB/T 15822 (all parts).

5.4.3 The residual magnetism of forgings should be detected by a Gauss meter.

5.5 Microstructure

5.5.1 The determination method of grain size shall comply with the provisions of GB/T 6394.

5.5.2 The detection method and evaluation of the depth of the decarburized layer shall comply with the provisions of GB/T 224.

5.5.3 The sampling location and evaluation of metallographic structure shall comply with the provisions of GB/T 13320. When the buyer has a request, the sampling location shall be determined through negotiation between the supplier and the purchaser.

5.6 Mechanical properties

5.6.1 If the purchaser has no special requirements, the test specimens shall be prepared from the forgings after forging and temperature-controlled cooling.

5.6.2 The interception direction of the test specimen shall be parallel to the metal flow direction of the forging; the sampling position and specimen preparation shall comply with the provisions of GB/T 2975; and the test methods for yield strength, tensile strength and elongation shall comply with provisions of GB/T 228.1.

A.1 Limited chemical composition

The purchaser shall limit the product analysis tolerance for one or more elements.

A.2 Limited incidental elements

The copper, nickel, chromium, molybdenum in the microalloyed steel or other elements specified in the purchase order shall not exceed the limits specified in the purchase order.

A.3 Non-metallic inclusions

The purchaser shall limit non-metallic inclusions; and the method for determining the content of non-metallic inclusions shall comply with the provisions of GB/T 10561. For vulcanized microalloyed steel, the maximum content of sulfide inclusions shall be determined through negotiation between the supplier and the purchaser.

A.4 Stress relief

When the supplier and the purchaser sides reach an agreement, the microalloyed steel shall be subjected to a cycle of stress relief treatment.

A.5 Impact test

A.5.1 The impact test method of forgings shall comply with the provisions of GB/T 229. The notch type, impact absorption energy and experimental temperature requirements shall be determined through negotiation between the supplier and the purchaser; and each group of tests contains 3 specimens.

A.5.2 The sampling location of the test specimen and the preparation of the specimen shall comply with the provisions of GB/T 2975.

A.6 Cleaning

The surface of the forgings shall be cleaned by shot peening or other suitable methods; and shall be subjected to anti-rust treatment. […]