“A number” refers to the chemistry of the weld for ferrous metals, i.e., carbon steels, high strength low alloys, stainless steels, etc... ASME Section IX addresses how the A number can be determined for several scenarios. In the case where the base metal is carbon steel and the weld is deposited using a matching shielded metal arc covered electrode, the A number listed in the PQR can be taken from the manufacturer's test results. There are other scenarios listed in Section IX for other situations. The one method that is acceptable in all cases is to have the weld deposit analyzed to determine the chemistry, and then select the appropriate A number using the table provided in Section IX.

In any event, anyone attempting to qualify a WPS to ASME has to have a copy of Section IX and the applicable construction code. The construction code is required to determine if notch toughness is an issue and if Charpy impact testing is required. The construction code can also modify the requirements of Section IX.

The nature of this query raises the question of why it has to be asked. There are two plausible reasons the question is asked. The first reason that comes to mind is that a copy of ASME Section IX is not available to find the answer sought. The second reason is that the individual asking the question does not have a working knowledge of Section IX. The corrective action in both cases is relatively simple. Purchase the relevant ASME code sections, i.e., Section IX and the applicable construction code, i.e., Section I, Section VIII, etc. For the second case, attend a class on Section IX to become more familiar with the requirements and how to comply with the code’s requirements. Education is not inexpensive. A person can become educated by attending the “School of Hard Knocks” or spend the time and money to attend a course that provides the training needed. The latter is usually the fastest and cheapest way of attaining the education sought.

My comments are not meant to be a "cheap shot" directed to the fellow asking the question. It is directed toward the employer that does not provide the employee with the tools needed to do their job. It is no different that the case where the welder is not provided with the proper tools to prepare the weld joint, the proper electrode to make the weld, or equipment that is in good working order.

Best regards - Al

Shane,
Section IX QW-404.5 permits A numbers to be determined from either the PQR as you mention, or the composition of the undiluted filler metal by one of several methods depending on the welding process.