Q1: What welding methods are suitable for Q235B welded pipe?
A1: Q235B welded pipe can be joined using common welding techniques such as shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and submerged arc welding (SAW). SMAW is widely used for its simplicity and portability, while GMAW provides faster deposition rates. SAW is preferred for thick-walled pipes due to deep penetration and high-quality welds. Preheating is generally unnecessary unless working in cold environments. Proper filler metals, such as E6013 or ER70S-6, should be used to match the base material's properties.
Q2: Can Q235B welded pipe be cold-formed or bent?
A2: Yes, Q235B welded pipe can be cold-formed due to its good ductility and low carbon content. However, excessive bending may cause deformation or cracking, so proper tooling and bending radius guidelines must be followed. For tight bends, heat-assisted forming may be used to reduce stress. Post-forming inspection is recommended to check for defects like wrinkling or ovality. Thinner-walled pipes are more susceptible to deformation than thicker ones.
Q3: What are the common defects in Q235B welded pipe fabrication?
A3: Common defects include porosity, slag inclusions, lack of fusion, and cracks. Porosity occurs due to gas entrapment, while slag inclusions result from improper cleaning between passes. Lack of fusion happens when the weld metal does not properly bond with the base material. Cracks may form due to excessive stress or hydrogen embrittlement. Non-destructive testing (NDT) methods like ultrasonic or radiographic testing help detect these defects early.
Q4: How should Q235B welded pipe be cut and machined?
A4: Q235B welded pipe can be cut using sawing, plasma cutting, or abrasive cutting methods. Sawing is precise and produces clean edges, while plasma cutting is faster for thicker pipes. Machining operations like drilling and threading require proper cooling to prevent overheating. Carbide tools are recommended for better tool life. Deburring and edge smoothing should be done to avoid stress concentrations.
Q5: What post-weld treatments are recommended for Q235B welded pipe?
A5: Post-weld treatments include stress relieving, grinding, and surface cleaning. Stress relieving reduces residual stresses that could lead to distortion or cracking. Grinding smooths weld beads for better aesthetics and fatigue resistance. Surface cleaning removes slag, spatter, and oxides to prepare for coatings. If galvanizing is required, pickling and fluxing must be done before dipping.
