Under what circumstances is it necessary to conduct mechanical property retesting for welding materials used in pressure equipment?
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I would like to ask: under what circumstances is it necessary to conduct mechanical property tests on welding materials for pressure equipment? How are such tests carried out, and are there any specific requirements and standards? Thank you
1. For steel in the normalized or normalized plus tempered condition with a thickness greater than 60 mm, an additional drop hammer test can be conducted on the weld metal produced from the welding materials. The test is carried out in accordance with GB/T6803, using P-2 type specimens; the acceptable criteria for the temperature at which no plastic transformation occurs (NDTT) are specified in the design documents. 2. For steel plates used to manufacture shells with a thickness of more than 50 mm in the quenched and tempered condition, or with a thickness of more than 100 mm in the normalized or normalized plus tempered condition, stricter requirements shall be specified for the impact tests on the weld joints of the resulting products. The design documents shall specify either option a) or b) below: a) The impact test temperature for the weld joint (including the weld seam and heat-affected zone) shall be at the design temperature, with impact performance criteria exceeding the minimum requirements specified in Table 1; b) The impact test temperature for the weld joint (including the weld seam and heat-affected zone) shall be lower than the design temperature, in which case the impact performance criteria shall comply with those specified in Table 1. 3. For welding materials used in the pressure-bearing components of pressure vessels, the high-temperature tensile properties and corrosion resistance (stress corrosion resistance) of the deposited metal shall not be lower than the relevant requirements specified for steel. Table 1 Impact performance indicators of non-alloy and alloy steel materials
I have seen your question and the replies below; the details provided by everyone regarding thickness, condition, and impact test requirements are indeed very important. However, the conditions for retesting mechanical properties are not limited to these; for instance, when there is a change in the batch number of the welding materials, performance fluctuations are detected during process qualification tests, or the thickness of the base material exceeds the range covered by the original qualifications, retesting is usually required as well. The specific implementation generally follows standards such as GB/T 150.4 and NB/T 47014, which specify the timing for re-inspection, the sampling locations, and the acceptance criteria. It is recommended that you check again the current versions of the design documents or relevant standards, as requirements can vary slightly across different industries (such as boilers and pressure vessels). If necessary, you may consult professional testing agencies or design firms for confirmation.
Minimum standard tensile strength value of steel (Rm) in MPa, Average impact energy absorption of 3 standard specimens (KV2) in J, Average lateral expansion value of 3 standard specimens (LE) in mm: >570–630, ≥20, —; >450–510, ≥24, —; >510–570, ≥31, —; >570–630, ≥34, —; >630–690, ≥38; ≥0.53 for values >690; ≥47, ≥0.53
The retesting of the mechanical properties of welding materials for pressure equipment is primarily carried out in two situations: when the inspection of the product’s welded specimens fails and double sampling is required for retesting, and when verification upon arrival at the site is necessary due to design/standard requirements or doubts regarding the quality； The welding materials are usually retested for the properties of the deposited metal, rather than directly for the mechanical properties of the finished product.