GB/T 37683-2019Large gear and girth gear forgings - Technical specification (English PDF)

4.2 Forging

4.2.1 The nozzle and riser of the ingot shall have sufficient removal, to ensure that the forging product has no shrinkage cavity, looseness, severe segregation, and other harmful defects.

4.2.2 Forgings shall be forged and formed on forging equipment with sufficient capacity, to ensure that the entire section of the forging is thoroughly forged and evenly organized.

4.3 Heat treatment

4.3.1 After the forging is forged, the supplier shall perform normalizing and high temperature tempering treatment.

4.3.2 The normalizing temperature of carburized steel forgings shall be higher than the carburizing temperature.

4.3.3 The supplier may, according to the material designation of forging and the ordering technical requirements, perform performance heat treatment or carburizing heat treatment.

4.4 Machining

4.4.1 Forgings shall be roughed or semi-finished prior to quenching and tempering or carburizing heat treatment.

4.4.2 The dimensions, tolerances, and surface roughness of the forgings shall

5.3 Hardness When forgings are only required to be accepted according to hardness, the hardness deviation of the same forging does not exceed 40 HBW. However, when the mechanical properties of forgings are required at the same time, the absolute value of hardness is not used as the basis for acceptance.

5.4 Nondestructive testing

5.4.1 General requirements Forgings shall be free of defects such as white spots, cracks, folds, shrinkage cavities, severe segregation which affect the use performance and surface quality.

5.4.2 Ultrasonic testing Forgings shall be subjected to ultrasonic testing before tooth punching after roughing and heat treatment. The testing results within the range of 20 mm or 1.5mn (when the modulus mn >12) below the tooth and root shall meet the requirements of the quality grade II of Table 1 of GB/T 37400.15-2019. The testing results of the remaining positions shall meet the Grade IV requirements.

5.4.3 Magnetic particle testing When the ordering technical agreement or the ordering contract has the requirement for magnetic particle testing, the magnetic particle testing shall be carried out by the purchaser. The testing method and acceptance criteria shall meet the requirements of the ordering contract or the ordering technical agreement.

5.5 Metallographic structure

5.5.1 Grain size When the inspection of grain size is required, it shall be indicated in the ordering contract. The inherent grain size of carburized steel shall not be coarser than Grade 5.0.

5.5.2 Nonmetallic inclusions When it is required to inspect nonmetallic inclusions, it shall be indicated in the ordering contract. The A, B, C, and D nonmetallic inclusions of forgings shall not exceed Grade 2.5. deformation, the direction of the tensile and impact samples shall be axial (longitudinal). When the ordering technical agreement or ordering drawing requires a tangential or transverse sample, the test results of the mechanical properties shall be lower than the specified values in Table 3 (longitudinal) by the percentage specified in Table 5.

b) For ring forgings, disc forgings, and the forgings mainly based on upsetting deformation, the direction of the tensile and impact samples shall be the direction of the main deformation, i.e. the tangential direction (circumferential direction).

6.2.3 Test methods

6.2.3.1 The tensile test shall be carried out in accordance with the provisions of GB/T 228.1.

6.2.3.2 The impact test is carried out in accordance with the provisions of GB/T 229.

6.3 Hardness inspection

6.3.1 The hardness inspection of forgings shall be carried out in accordance with the provisions of GB/T 231.1. The hardness inspection of hardened samples shall be carried out in accordance with the provisions of GB/T 230.1. Vickers hardness inspection shall be carried out in accordance with the provisions of GB/T 4340.1.

6.3.2 At least two places shall be measured at the end face of the girth gear forging and about 1/4 of the diameter from the outer surface; the two places are 180° apart. If the forging is larger than phi3000 mm in diameter, at least four places shall be measured, each at a distance of 90°. The hardness of gear or gear shaft forgings shall be measured at four places on the outer surface to be tooth-punched, 90° apart.

a) When performing a V-notch impact test, if the arithmetic mean of a set of impact samples is not lower than the specified value, and one of the values is not less than 70% of the specified value, retest may not be performed. When the above requirements are not met, a set of three impact samples may be taken in the adjacent part of the previous sample for retesting. The arithmetic mean of the two sets of samples shall not be lower than the specified requirement. The number of single values below the specified value shall not exceed two. Only one single value is allowed to be less than 70% of the specified value;

b) When performing a U-notch impact test, if a certain test result is unqualified, double quantity of samples may be taken in the adjacent part of the previous sample for retesting. The retest results of the two samples shall conform to the regulations.

6.6.3 If the inspection of mechanical properties is unqualified due to white spots and cracks in the sample, retest shall not be conducted.

6.7 Reheat treatment When the inspection result of any mechanical property of the forgings is still unqualified, reheat treatment may be carried out; re-sampling shall be carried out for test. The number of reheat treatments shall not exceed two at most. The number of tempering is not limited.

7.1 Acceptance

7.1.1 The supplier shall provide the necessary conditions for purchaser's acceptance personnel, for the purchaser's acceptance personnel to carry out the on-site inspection work. The purchaser's inspection personnel shall not hinder the production of the supplier.

7.1.2 The purchaser has the right to select certain test items of forgings for acceptance. During the acceptance inspection or the subsequent processing or inspection, if it is found that the forgings do not meet the supplementary technical requirements specified in this Standard and in the ordering contract, the purchaser shall promptly notify the supplier; the two parties shall negotiate to resolve.