GB/T 12230-2023General purpose industrial valves - Specification of stainless steel castings (English PDF)

4.2 Casting process and evaluation

4.2.1 Casting process The casting process shall be evaluated and qualified before being used in mass production of castings.

4.2.2 Casting process evaluation

4.2.2.1 Casting process evaluation shall be carried out in the following cases.

a) the first production of the mold;

b) major changes in the casting process design, such as the gate and riser system;

c) changes in production process conditions, such as site, smelting equipment, etc.;

d) casting defects related to process design are found in mass production.

4.2.2.2 The casting process evaluation report shall at least include the following.

a) casting process design documents;

b) heat treatment records or reports;

c) chemical composition and mechanical properties test reports;

d) dimensional inspection report;

e) appearance inspection report;

f) penetrant testing report;

g) radiographic testing report. completely removed during machining, and the internal cooling iron shall not change the material of the casting and cause cracks.

4.9 Shell test The acceptance criteria for shell test shall comply with the provisions of GB/T 13927 or GB/T 26480.

4.10 Repair welding

4.10.1 Repair welding of castings shall be carried out in accordance with the evaluated welding process specifications, and the welding process evaluation shall be carried out in accordance with NB/T 47014.

4.10.2 Welders who repair castings shall pass the examination and hold the corresponding qualification certificate in accordance with the requirements of GB/T 15169.

4.10.3 The repair welding area and its heat affected zone after repair welding shall be inspected, and the acceptance criteria shall not be lower than the requirements of castings.

4.10.4 The following repair welding is a major repair welding.

a) the depth of the pit to be repaired exceeds 20 % of the wall thickness of the casting or 25 mm, whichever is smaller;

b) the area to be repaired is greater than 65 cm2.

5.1 Chemical composition analysis

5.1.1 Smelting analysis Each smelting heat number shall be subjected to smelting chemical composition analysis, and samples shall be taken during the pouring process. The sampling method shall comply with the provisions of GB/T 20066 or GB/T 5678.The chemical analysis method shall comply with the provisions of Table 7 in GB/T 16253-2019.The chemical composition analysis results shall comply with the provisions of Table 1.

5.1.2 Finished product analysis Take representative samples from each heat number, each batch or each casting for chemical composition analysis. The sampling method and chemical analysis method shall comply with the provisions of 5.1.1. The allowable deviation of finished product analysis shall comply with the provisions of GB/T 222.

5.2 Mechanical properties test

5.2.1 Test coupon The test coupon shall comply with the provisions of

3.7 in GB/T 16253-2019.

5.2.2 Tensile test The room-temperature tensile test method and specimens shall comply with the provisions of GB/T 228.1.For castings of the same smelting heat number and the same heat treatment batch number, one specimen shall be taken for tensile test, and the test results shall comply with the provisions of Table 2.

5.2.3 Retest

5.2.3.1 If the room-temperature tensile test results do not comply with the provisions of Table 2 due to the following reasons, the test results are invalid. Take another specimen from the same test coupon or another test coupon of the same heat number for test, and the test results shall comply with the provisions of Table 2.

a) the specimen is defective or the testing machine does not function properly.

b) the specimen has processing defects.

c) the tensile specimen is broken outside the gauge length.

5.2.3.2 When the room-temperature tensile test results do not comply with the requirements of Table 2 and are not the cases listed in 5.2.3.1, it can take two specimens from the original test coupon or another test coupon of the same furnace for test. The test results of the two specimens shall comply with the provisions of Table 2.

5.2.4 Reheat treatment When the room-temperature tensile test or retest results do not meet the requirements of Table 2, it is allowed to reheat the castings and test coupons for test. Reheat treatment shall not exceed two times. The test results after reheat treatment shall meet the requirements of Table 2.

5.3 Dimension inspection Dimension inspection can be measured by tools such as calipers.

5.4 Appearance inspection Visually inspect the inner and outer surfaces of the castings. The surface roughness assessment method shall comply with the provisions of GB/T 15056.

5.5 Shell test Shell test method shall comply with the provisions of GB/T 13927 or GB/T 26480.

6.1 Marking

6.1.1 The castings shall be marked in the form of cast characters. The content, position and size of the cast characters shall comply with the drawing requirements of the purchaser.

6.1.2 When the unit weight of the casting is less than 20 kg and it is difficult to mark the cast characters, low-stress steel stamps may be used for marking with the consent of the purchaser.

6.2 Quality certificate The delivered castings shall be accompanied by a quality certificate, the contents of which shall include but are not limited to.

a) name of supplier;

b) serial number of this document and material designation;

c) casting name, model specification or drawing number, mold number (if any);

e) heat treatment status;

f) chemical composition;

g) mechanical properties;

h) inspection and test reports (if any) required by the contract or order.