CSWIP 3.1 Welding Fundamentals

CSWIP 3.1 Leading Questions

• Welding activities considered essential for checking include amperage, cleaning dimensions, pre-heat treatment (PWHT), consumable control, heat input, run-out length, polarity, inter-pass temperature, and the run sequence. Voltage, cleaning, electrode size, post-cleaning, and checking welding equipment are also important.
• Among these, heat input has the most significant influence on HICC (Heat Input to Cooling rate).
• A root radius is used in single V and open square edge butt joint types.
• Open square edge butt has an included angle of 60 to 70 degrees, a bevel angle of 25 to 30 degrees.
• The difference between actual throat thickness and design throat thickness in fillet weld is usually approximately 20%. This difference is related to penetration level.
• The relationship between design throat thickness and leg length is derived from a concave fillet weld.
• In mechanical testing, the Charpy impact test in multi-positional welds is taken from the PA position. This position offers a higher hardness level.
• The HAZ (Heat Affected Zone) of a V butt weld consists of two distinct affected areas. This is a grain growth zone, recrystallized zone and partially transformed, tempered zone.
• Factors that lead to hydrogen cracking include : <250HV hardness or value, <300 C temperature, 0.5 yield stress, 15ml of H2 100 gram of weld metal.
• Low amperage, slow travel speed, and low arc voltage, cause porosity in welding.
• Lack of fusion during MAG welding is often associated with long background current duration, low current and arc extinguishing, and high deposit rates.
• The PF (Flat) welding position in MAG (metal active gas) welding is more likely to result in lack of fusion due to the gravitational pull of the weld pool running in front of the arc, lower welding current, and higher thermal conductivity.
• Welding qualification tests may involve tensile and fracture tests. Macro and Charpy tests are also common. Quantitative and qualitative testing methods are used.
• In tensile tests on C-Mn steel, the following properties are measured: Re (yield strength), Rm (ultimate tensile strength), Rp (proof stress), and elongation (A%).
• In Charpy testing, the transition temperature is midway between the upper and lower shelf of the transition temperature curve.
• Hardness testing is done to assess the susceptibility of the material to cracking and lamellar tearing.
• The hardness of the material plays a role in solidification cracking.
• The hardness test helps to assess if there is risk of cracking, lamellar tearing , fatigue failure and solidification cracking in metals.
• The hardness test helps to assess the susceptibility of the component material to cracking and fatigue failures.

Other Leading Questions

• The hardness testing is performed on C-Mn steel in Mechanical Testing.
• For welding on a horizontal fixed axis pipe, hardness is tested on the PA position because high heat input is used.
• Slag inclusions, cracks, and porosity are difficult to detect using Radiography. Undercuts are usually easy to detect using some other testing techniques.
• Magnetic particle inspection (MPI) is effective in detecting internal lack of fusion, surface cracks, and lack of inter-run fusion and internal slag inclusion.
• In MMA (metal-arc) welding, AC current can be used by transformer-rectifier type equipment to power the welding process. For this application AC current needs a transformer before being used in the welding process.
• The preferred polarity for TIG welding aluminum is AC because it results better in welding compared to DC. During DC welding aluminum, cathode cleaning can result in tungsten inclusions.
• In MIG/MAG welding, increasing the inductance decreases arc-on time.
• Exothermic chemical reactions occur at the temperature slightly above the material's melting point in oxy-fuel cutting.
• COSHH (Control of Substances Hazardous to Health) legislation requires employees to keep a register of hazardous substances, ensure they are used in a safe manner, and ensure that safety zones around the workplace are properly maintained.
• In cross-sectional dimensions for weld symbols, the locations should be marked to the left or *right of the symbol, depending on the symbol type.
• MIG/MAG welding has the broadest range of consumables due to the use of different wire spools.
• The heat input for qualified welds, in an EN welding procedure standard that requires impact testing, needs to be within 20% below or 25% below the lowest values. This is because to avoid the material becoming too hard, the material should retain toughness.
• Current values for SAW (Submerged Arc Welding) process are higher due to no energy loss across the arc and fast travel speed.
• S355J2GS steel has a yield strength of 355 MPa.
• Steel grade, S355J2GS, should not be used in environments above 40 degrees Celcius.
• Some parts of a MIG/MAG torch include a nozzle, spatter protection, welding gun assembly, gas diffuser, contact tip, spot welding spacers, welding gun body, and an on/off switch.
• Measuring Rel or Reh (yield strength), Rm (ultimate tensile strength), Elongation in tensile testing.
• Heat treatment should be performed after 48 hours of welding to improve the resistance against hot cracking, lamellar tearing, and cold cracking, and ductile failure.
• External/internal defects can be detected on pipes using NDT techniques such as UT, RT, MT, and PT.
• The issue of using a different material such as 316L instead of the intended material can lead to solidification cracking or poor through-thickness ductility leading to issues in weld.