Physical Metallurgy -Understanding on Heat Treatment of Steels

A: Picking wrong here sets you up for brittle cracking during pressure hold, followed by a non-reportable becoming reportable. Sulfide stress cracking tracks hardness and residual stress. Subcritical stress relief drops locked-in stress without creating high-hardness phases, keeping hardness under NACE limits. Martensite, even tempered poorly, pushes hardness and trap density up. Normalizing refines grains but doesn't control residual stress enough for wet H2S unless hardness is verified.

A: Choosing poorly means variable hardness across plates, coating holidays, and early underfilm corrosion. Normalizing evens out microstructure and chemistry after hot work, giving consistent surface condition and yield strength. Full anneal leaves coarse grains that dent and trap moisture. Quenching without tempering introduces stress and cracking risk. Austempering is rarely controlled well at plate scale and complicates inspection.

A: Jumping straight to rejection or derating can shut down commissioning with no safety gain. Field hardness readings swing with calibration, surface condition, and operator technique. Verifying the tester and grind finish addresses the most common error path first. Only after confirming the measurement chain do material mix-up or heat treatment drift become credible risks.

A: Misjudging this leads to unexpected hardness gradients and failed impact tests. Plain carbon steels have critical cooling rates that oil can meet at modest thicknesses. At 20 mm, through-thickness martensite is feasible depending on carbon content. Water isn't mandatory, and alloying shifts curves but isn't a prerequisite.