Lesson 1Microstructural zones in welded joints: fusion zone, HAZ, base metalIt explains how welding makes different inner zones in 304L stainless steel, how the melted zone, heat-affected area, and main metal differ in makeup and grain setup, and why these matter for strength and weld work.
Solidification in the fusion zoneHAZ grain growth and recrystallizationBase metal austenitic microstructureDelta ferrite formation and morphologyMicrostructural gradients across the weldLesson 2Thermal cycles during welding: peak temperatures, cooling rates, and their metallurgical effectsLooks at heat cycles in 304L welding, peak heat levels, heating and cooling speeds, and how they change grain growth, delta ferrite, carbide buildup, leftover stresses, and final inner structure across the weld.
Thermal cycle profiles in weld passesCooling rate effects on microstructureGrain growth and refinement in the HAZInfluence on delta ferrite and austeniteThermal cycles and residual stress buildupLesson 3Typical chemical composition and ranges for 304L (Cr, Ni, C, Mn, Si, P, S, N)Lists usual chemical makeup ranges for 304L, like chromium, nickel, carbon, manganese, silicon, phosphorus, sulfur, and nitrogen, and shows how each affects welding ease, rust resistance, and strength.
Standard composition ranges for 304LRole of chromium in corrosion resistanceNickel effects on austenite stabilityCarbon, nitrogen, and strength balanceImpurities and control of P and SLesson 4Galvanic and bimetallic corrosion when joining stainless to carbon steelExplains electric and two-metal rust when joining 304L to carbon steel, covering electric series ideas, area effects, weld design, and protections like insulation, coatings, and right filler choice.
Galvanic series and potential differencesArea ratio and geometry considerationsCrevice and underdeposit corrosion risksUse of insulation and barrier materialsCoatings and cathodic protection optionsLesson 5Mechanical properties: yield, tensile strength, elongation, hardness, and temperature effectsDescribes how welding changes yield strength, pull strength, stretch, and hardness in 304L, including cooling speed, leftover stresses, and work heat effects on bendability, toughness, and shape change.
Typical mechanical properties of 304LProperty variation across weld zonesWork hardening and strain-induced martensiteEffects of low and elevated temperaturesResidual stresses and distortion impactLesson 6304 vs 304L: carbon content impact and sensitization mechanismsCompares 304 and 304L, key on carbon limits, carbide buildup, and rust risk, and tells when low-carbon types or other fixes are needed for welded use.
Carbon limits in 304 versus 304LCarbide precipitation tendenciesWelded service and grade selectionUse of stabilized alternative gradesCode and specification requirementsLesson 7Sensitization: chromium carbide precipitation, critical temperature range, and consequencesLooks into rust weakening in 304L, chromium carbide buildup on grain edges, key heat range, time effects, and grain rust results, plus ways to stop or fix it.
Critical temperature range for sensitizationTime–temperature–sensitization curvesIntergranular corrosion mechanismsPostweld heat treatment strategiesDesign and procedure steps to avoid itLesson 8Effect of filler metal chemistry on corrosion resistance and metallurgical compatibilityCovers how filler chromium, nickel, molybdenum levels affect rust resistance, ferrite balance, hot cracks, and matching filler for work needs and mixed joins.
Common filler grades for 304L weldsOvermatching versus matching chemistryFiller effects on delta ferrite contentInfluence on hot cracking resistanceFiller selection for dissimilar jointsLesson 9Corrosion resistance mechanisms and how composition/heat input affect themDetails protective film on 304L, how chromium, nickel, molybdenum affect rust fight, and how heat, mixing, surface change pit, gap, general rust.
Passive film formation and repairRole of chromium and nickel in passivityHeat input effects on corrosion behaviorSurface condition and postweld cleaningDilution with base metal and its impactLesson 10Overview of hydrogen, nitrogen, and oxygen pickup effects in stainless weldingTalks how hydrogen, nitrogen, oxygen get in during 304L welding, from gas shield or dirt, effects on holes, cracks, nitrogen loss, oxide, strength.
Sources of hydrogen in stainless weldingNitrogen behavior in austenitic stainlessOxygen pickup and oxide formationEffects on porosity and cracking riskShielding gas and cleanliness control
