Impact of Welding Standards on Heat Affected Zone: A Critical Review of the Methods, Consumables, and Environmental Degradation on the Performance of API 5L X52 in Sour Service

Table 2. Analysis of Heat Input vs.HAZ Properties

Analysis Category	Parameter Relationship	Key Results	p-value	R²	Confidence Interval (95%)	Interpretation
HAZ Width vs. Heat Input	HAZ Width = 0.85 × Heat Input + 1.2	Coefficient: 0.85 ± 0.05	<0.001	0.87	[0.78, 0.92]	Strong positive correlation
Max Hardness vs. Heat Input	Max Hardness = -28.5 × Heat Input + 268	Coefficient: -28.5 ± 2.1	0.002	0.73	[-32.7, -24.3]	Significant inverse relationship
HAZ Toughness vs. Cooling Time	Charpy Energy = 4.2 × t₈/₅ - 0.15 × t₈/₅²	Peak at t₈/₅ = 14s	<0.001	0.82	[12s, 16s]	Optimal toughness window