What items must the PQR address at a minimum?

The procedure qualification record (PQR) must address essential variables as they are critical for ensuring that the welding procedure meets defined mechanical and physical properties for the weld. Essential variables include factors such as base material type, filler material, welding process, joint design, and heat treatment, which directly affect the integrity of the weld and final product performance.

Additionally, when notch toughness testing is required, this also becomes an essential aspect that must be included in the PQR. Notch toughness testing assesses the weld's ability to withstand impact loading, which is vital for certain applications where the material may experience such conditions. This comprehensive coverage in the PQR helps ensure that the welded construction will meet the necessary specifications and standards for safety and performance in service.

In contrast, focusing solely on non-essential variables or environmental conditions, as suggested in other options, does not encompass the critical aspects needed for effective procedure qualification. Non-essential variables can vary without affecting the capability of the welding procedure to meet performance requirements, while environmental conditions and electrode types may not necessarily be pivotal in certain applications. Furthermore, limiting the PQR to only testing results neglects the comprehensive documentation required for quality assurance in welding procedures.