Inspection items and main purposes of welding procedure qualification

Date：2022-08-10 18:11:05Views：1426

Welding test piece and test piece inspection

(1) The welding test piece must be carried out in strict accordance with the requirements and regulations of the process qualification scheme under effective supervision.

(2) During the welding process, each step shall be carefully recorded by a specially assigned person, and a parameter recorder capable of saving the recorded data shall be provided for recording. The records shall be properly kept for approval.

(3) The inspection items must be complete and carried out according to the requirements of relevant regulations.

The main inspection items are:

1) Weld appearance inspection: the reinforcement of weld metal shall not be lower than the base metal, the depth and length of undercut shall not exceed the standard, and the weld surface shall be free of cracks, incomplete fusion, slag inclusion, arc crater and air hole.

2) Non destructive testing of welds: radiographic testing of tubular test pieces shall be carried out according to DL / t821, and the weld quality shall not be lower than class II standard. Non destructive testing is not related to the mechanical properties of welded joints, but it is necessary to understand the welding defects in the "evaluation". At the same time, it is also necessary to avoid it when cutting test pieces. Therefore, it is necessary to include it in the inspection items. The main purpose of fracture inspection is to check the macro welding defects of the weld metal section, which belongs to the measurement scope of the welder's operation skills and cannot be directly used to determine the mechanical properties, so it is cancelled.

3) Tensile test (size sample)

① The reinforcement of the sample shall be removed by mechanical method and shall be flush with the base metal.

② Thickness of test piece: when the thickness is less than 30mm, the full thickness test piece can be used; when the thickness is more than 30mm, two or more test pieces can be processed.

③ The tensile strength of each sample shall not be lower than the lower limit of the base metal.

④ The tensile strength of the dissimilar steel sample shall not be lower than the lower limit of the base metal on the lower side.

⑤ Two or more specimens shall be subject to tensile test, and the average value of each group of specimens shall not exceed the lower limit of the specified value of the base metal.

4) Bending test

① The bending specimen can be divided into transverse plane bending (back), longitudinal plane bending (back) and transverse side bending.

② When t is less than 10, t = t; When t is greater than t, t = 10. Width of specimen: 40, 20, 10 (unit: mm).

③ The reinforcement of the sample shall be removed by mechanical method, and the original surface of the base metal shall be maintained. Undercut and weld root notch shall not be removed.

④ If there are defects on the lateral side bending surface, the more serious one shall be measured as the tensile surface.

⑤ The three main factors affecting the bending test are the ratio of width to thickness, bending angle and bending axis diameter. The bending test method and relevant provisions of sd340-89 specification do not correspond to the elongation of the material itself. Therefore, the elongation of the bending outer surface of the sample has exceeded the lower limit of the elongation for some steels, so it is not reasonable.

In order to make the bending test more reasonable for the determination of plasticity, the following provisions are made in the new specification: the bending test method shall be carried out according to GB / t232 metal bending test method.

The bending test conditions are specified as follows: specimen thickness ≤ 10, bending shaft diameter (d) 4T. Bearing spacing (LMM) 6T + 3, bending angle 180 °.

For the steel with the lower limit of elongation less than 20% specified in the standard and technical conditions, if the bending test is unqualified and the measured elongation is less than 20%, it is allowed to increase the diameter of the bending shaft for testing. After bending to the specified angle, the tensile surface of each specimen shall not have cracks with a length of more than 3mm in any direction in the weld and heat affected zone, except for the cracks on the edges and corners, but the cracks caused by slag inclusion defects shall be included.

5) Impact test: impact test shall be conducted for pressure bearing and load-bearing parts as long as they have the conditions for impact test. Therefore, when the following conditions are met:

① If the thickness of the weldment is insufficient for sampling (5 × 10 × 5mm), it can be omitted.

② When the thickness of the weldment is ≥ 16mm, the impact test shall be carried out. 10? 0 5mm.

③ Qualification criteria: the average value of three samples shall not be lower than the lower limit specified in relevant technical documents, and one of them shall not be lower than 70% of the specified value.

6) Metallographic inspection: the tube sheet is corner connected, and the same notch shall not have two inspection surfaces.

7) Hardness test: the hardness of weld and heat affected zone shall not be less than 90% of the hardness value, not more than the Brinell hardness of base metal plus 100hb, and not more than the following provisions:

When the total alloy content is less than 3%, the hardness is less than or equal to 270hb

When the total alloy content is equal to 3 ~ 10, the hardness is less than or equal to 300hb

When the total alloy content is greater than 10, the hardness is less than or equal to 350hb

P91 steel 220 ~ 240 is the best

(4) The preparation, cutting and evaluation of the above samples shall be carried out according to relevant standards.

(5) After the inspection, a formal report must be issued by personnel with corresponding qualifications.

(6) The inspection procedures and requirements must comply with the regulations.

Purpose of welding procedure qualification:

1. Evaluate whether the welding unit has the ability to weld the welded joints that meet the requirements of relevant national or industrial standards and technical specifications;

2. Verify whether the welding process instruction prepared by the welding unit is correct;

3. Provide reliable technical basis for formulating formal welding process instruction or welding process card;

4. Assess the welder's ability.

The above is the relevant content of x-welding process qualification test compiled by Chuangxin testing group. I hope it will be helpful to you. Our company has professional engineers and industry elite teams, and has three standardized laboratories with an area of more than 1800 square meters. It can undertake various test projects such as electronic component testing and verification, IC authenticity identification, product design and material selection, failure analysis, functional testing, factory incoming material inspection and tape weaving.