GB/T 37682-2019Large exposed gear steel castings - Technical specification (English PDF)

4.4 Defect removal and repair welding

4.4.1 Casting defects are allowed to be repaired by repair welding. Before repair welding, the defects shall be cleaned, and confirmed by magnetic particle testing or penetrant testing whether to meet the requirements of repair welding.

4.4.2 The repair welding of casting defects shall be carried out by qualified operators in accordance with the process requirements. Before repair welding, generally, it shall carry out the welding procedure qualification.

4.4.3 After the defect is removed, if the depth exceeds 25 mm or exceeds 40% of the section thickness, it shall be regarded as a major defect. It shall record the repair welding of the major defect.

4.4.4 After the repair welding of the defect, it shall carry out the stress relief heat treatment. The repair welding zone shall be tested according to the non- destructive testing standard of the casting, to confirm the quality of the repair welding.

4.4.5 Upon agreement between the supplier and the purchaser, the defect treatment after casting finishing may be carried out with reference to Appendix A.

5.1 Chemical composition

5.1.1 The chemical composition of each cast steel designation shall comply with the requirements of Table 1.

5.1.2 Unless otherwise specified, the residual element content is not used as the basis for acceptance.

5.1.3 When required by the purchaser, the chemical composition analysis of the product may be carried out. The permissible tolerances for chemical composition of products shall meet the requirements of GB/T 222. According to the ordering requirements of the purchaser, the castings may be subjected to magnetic powder, penetrant, and ultrasonic testing. The required testing methods, testing positions, and acceptance quality levels are mutually agreed by the supplier and the purchaser.

5.4 Surface quality

5.4.1 It shall clean the casting surface. There shall be no defects such as burnt- on sand, cracks, cold shut. It shall correct the burr of the casting and remove the scale.

5.4.2 The surface roughness Ra shall be less than or equal to 50 µm. The surface to be non-destructively tested shall meet the requirements of non- destructive testing.

5.5 Shape, dimensional tolerances, mass tolerances

5.5.1 The casting shape shall meet the requirements of the ordering drawings. The dimensional tolerances of the casting shall meet the requirements of GB/T 6414. The tolerance grade is generally Grade DCTG14. The special grade is agreed by the supplier and the purchaser.

5.5.2 The rim wall thickness and joint plate wall thickness of the casting shall be uniform. The thinnest shall not be less than 5% of the wall thickness required by the drawing. The thickest shall not be greater than 10% of the wall thickness required by the drawing.

5.5.3 If a process supplement is finally retained, the mass tolerances of the casting are not used as the basis for acceptance. In special cases, the mass tolerances of the casting are agreed by the supplier and the purchaser.

6.1 Chemical composition

6.1.1 The melting chemical composition shall be sampled and inspected according to the melting heat. Samples for chemical composition analysis of products may be taken from the test lug or the position at least 6 mm below the casting surface. When a casting is cast in multiple ladle, it shall analyze each ladle. The analysis results of each ladle shall meet the composition requirements of the selected designation.

6.1.2 Chemical analysis sampling shall be in accordance with the provisions of GB/T 20066; the analysis shall be in accordance with the provisions of GB/T 223. Spectrochemical analysis sampling shall be in accordance with the

6.6.2 When the tensile test fails, 2 standby tensile samples are taken from the same heat to be tested. If the 3 test results are in accordance with Table 2, the tensile properties of the castings of this heat are still qualified. If 1 of the samples still fails the retest, the supplier may handle as specified in 6.7.

6.6.3 When the impact test fails, 3 standby impact samples are taken from the same heat to be tested. The result is added to the previous result to recalculate the average, which shall meet the requirements of Table 2. No more than 2 of the 6 impact values is lower the specified average. No more than 1 is lower 70% of the specified average. Otherwise, it will be judged as unqualified; the supplier may handle as specified in 6.7.

6.6.4 In the hardness inspection, if there is a value below the specified minimum hardness value on any prime line or the hardness difference between the points exceeds 40 HBW, on both sides of the prime line, the test shall be doubled. If the test results meet the requirements of Table 2, the casting hardness is qualified. Otherwise, the supplier shall submit the actual distribution of the hardness value to the purchaser for evaluation. If the purchaser evaluation is not passed, it shall be handled according to 6.7.

6.7 Reheat treatment When the retest result of mechanical properties still does not meet the requirements of Table 2, the casting and the test bar may be heat treated again and then retested in accordance with

6.2 and 6.3. Without the consent of the purchaser, the number of reheat treatment shall not exceed 2 times (except tempering).