Please elaborate a detailed explanation of Groups 1, 2, 3, and 4 under P-Number 1 as listed in Table QW/QB-422 of ASME BPVC Section IX? What are the criteria for categorizing materials into these groups, and how does each group differ?

Criteria for Categorizing Materials into Groups:

a. Chemical Composition:
Grouping is influenced by the amounts of elements like carbon, manganese, sulfur, phosphorus, and other alloying elements.
Steels with similar chemical properties are grouped to ensure compatibility during welding.

b. Mechanical Properties:
Yield strength, tensile strength, and toughness are key factors.
Materials with comparable mechanical properties are grouped together to standardize qualification ranges.

c. Weldability:
Materials with similar weldability, including susceptibility to cracking or requirements for preheat and post-weld heat treatment (PWHT), are placed in the same group.

d. Heat Treatment:
Materials that respond similarly to heat treatment, such as annealing or normalization, are categorized together.

e. Applications:
Certain groups are tailored for specific uses, such as piping, pressure vessels, or structural components.