The China Classification Society (CCS) sets stringent requirements for welding procedures used on Grade B Shipbuilding steel plates, which are extensively employed in hull structures, superstructures, and deckhouses. A properly qualified welding procedure is mandatory before any production welding can commence, as it ensures that the resulting joints possess the necessary mechanical properties and defect‑free integrity to withstand the harsh marine environment. This article outlines the key steps and criteria for qualifying a welding procedure for CCS Grade B plates.
The qualification process begins with the preparation of a Welding Procedure Specification (WPS) . The WPS must detail all essential variables, including base metal grade and thickness, joint design, groove angle, root gap, welding position, preheat temperature, interpass temperature, heat input range, and the classification of filler metals. For CCS Grade B, the carbon equivalent (CE) is typically ≤0.38%, which reduces the risk of cold cracking. Plates up to 50 mm thick generally do not require preheating, but if the CE exceeds this limit or the thickness is greater, preheat temperatures must be specified and verified during testing.
The next critical step is the fabrication of test coupons. These must be welded using the exact parameters stated in the WPS, employing the same consumables, equipment, and operator skill level that will be used in production. CCS requires that the test welds be subjected to both non‑destructive testing (NDT) and destructive testing. NDT typically includes ultrasonic testing (UT) and magnetic particle inspection (MPI) to detect internal and surface discontinuities. The acceptance criteria follow CCS rules, which are often more demanding than some international standards, particularly regarding the sizing and nature of indications.
For destructive testing, the procedure must qualify via tensile tests, bend tests (face and root), and macro‑etch examinations. Tensile specimens must achieve ultimate strength at least equal to the specified minimum for Grade B (400–520 MPa). Bend tests require that the weld and heat‑affected zone (HAZ) show no cracks exceeding 3 mm after bending to a prescribed angle. Macro‑etch specimens must reveal complete fusion and freedom from porosity, slag inclusions, or lack of penetration. In addition, Charpy V‑notch impact testing may be required for certain thicknesses or service conditions, typically at 0°C with a minimum average energy of 27 J.
All welding consumables—electrodes, fluxes, and shielding gases—must be CCS‑approved and traceable. The qualification report, along with the WPS, must be submitted to CCS for review and final endorsement. Once approved, the procedure is valid for a specific range of thicknesses and joint configurations, provided that no essential variable changes occur. Should any modification be made—such as a different filler metal or increased heat input—the procedure must be re‑qualified.
In conclusion, qualifying a welding procedure for CCS Grade B plates demands meticulous documentation, rigorous testing, and strict adherence to CCS rules. This thorough approach guarantees that welded joints in ship hulls will perform reliably under cyclic loading, corrosive seawater, and low temperatures, thereby safeguarding the vessel and its crew.
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