Regulations for welding process approval in shipbuilding
In the process of shipbuilding, welding process evaluation test is usually carried out for the determined base material and welding materials. After certain technological welding, the applicability of the process is evaluated by checking the properties of welding seam and heat-affected zone. As welding process evaluation is great significance to ensure the quality of subsequent welding production. Each classification society requires to evaluate or approve the newly adopted welding process. For example, according to materials and welding specifications of China classification society (1998); Before welding, the manufacturers of ships.
Usually before a ship starts to be built. The factory should work out the ship construction welding process schedule . And submit it to the surveyor for approval according to its own technical conditions and production experience. In the schedule, the welding process name and number to use shall be list according to the different positions, forms and sizes of welding seams appearing in important structures and joints during construction. Compared with the previous welding process evaluation in this factory. The welding process evaluation test organize for the unapproved process or the process beyond the scope of application of the welding process evaluation.
Welding process evaluation and implementation
Submit welding procedure evaluation test plan:
Before the welding procedure assessment, the factory shall first submit a welding procedure assessment test plan; In order to approved the classification society, which usually includes the following contents:
(1)Brand, grade, thickness and delivery status of parent material.
(2) Model, grade and specification of welding materials (electrode, wire, flux and shielding gas).
(3) Welding equipment model and main performance parameters.
(4) Groove design and processing requirements.
(5) Bead layout and welding sequence.
(6) Weld area(horizontal, vertical, horizontal, overhead, etc.).
(7)Solding specification parameters (power polarity, welding current, arc voltage, welding speed and protective gas flow, etc.).
(8) Preheating before welding, temperature control between channels, post-welding heat treatment and post-welding stress relief measures, etc. (if necessary).
(9) Welding environment (such as on-site welding, workshop welding or laboratory welding).
(10) Post-welding inspection/test items and requirements;Intercept location map and processing size map of each sample in the test project.
(11) Other relevant special requirements.
Classification society will mainly rely on CCS
The main content of inspection is: the welding process is basically correct. The sample location of the project interception is consistent with the specification requirements. Before filling in the welding specification parameters, please refer to the relevant information. In addition, each plant will normally conduct its own preliminary test of the proposed project before applying for the welding procedure assessment. After receiving the welding process test plan, the classification society will review the plan according to the rules of the classification society. If the content of China ship welding procedure evaluation program fill in. The data of pre-test can also be referred to. After the welding process plan completed, it shall be submitted to the classification society for review.
Review of welding procedure evaluation test program by classification society
Whether the test can meet the specification requirements.Go the test processing can meet the specification requirements. If the limited value of each test result meets the specification requirements.
In addition, in the review of welding process test program, usually also requires the base material and welding materials as far as possible to choose by classification society or inspection qualified materials. Since the weldability of these materials has been investigated by the classification society in the factory evaluation of the planks and welding materials manufacturers. The selection of these assessed/tested materials can reduce the influence of uncertain factors in the welding process evaluation process.
After review of the welding process evaluation scheme, the classification society will submit the review opinions to the factory. Which will modify and improve the welding process test scheme according to the review opinions, and prepare for the field test.
Conduct welding procedure qualification field test
The welding procedure qualification field test shall carried out in accordance with the reviewed wpa test scheme.Before start of the test, the surveyor shall check whether the base material to weld; And the welding material are consistent with the grade and specification of the material in the scheme. Check the assembly status of the welding specimen, whether it meets the requirements of the scheme. Power welding, also check the correct polarity of the power supply.
During the test, the layout of each weld pass, welding parameters and whether preheated. Temperature control between layers, weld pass laying and root clearing shall be recorded. And the appearance quality of the weld shall evaluated. If the appearance of welding test plate qualified, nondestructive testing will carried out on the welding seam. And the positions of tensile, bending, impact and metallographic test specimens shall determine on the welding test plate. The last step is to check the processing status of the sample and conduct physical and chemical properties test.