Key notes:

General:

Weldability depend on Carbon and alloy elements

Poor weldability mean –> the occurrence of cracking

Alloying elements:

Carbon

Most effect to the Hardness 

Hardness is invert proportion Ductility 

 

%C typical <~ 0.25-0.3%

%CE or CVE ~ 0.4-0.5%

Manganese

De-sulfure –> reduce rick of Hot cracks (Solidification Crack)

C-S (<0.8% Mn) vs C-Mn-S (<1.6% Mn)

Molybdenum

• For Creep resistance  (at High temp operation)

 

HIC

Higher susceptible in Alloy C-S (crack in weld) than C-S (crack in HAZ)

Chevron (arrow) crack most occurred in SAW

HIC never happen in Ni/Cu alloy (they can’t be harden by heat)

Hydrogen level depends on Welding processes:

Solidification Cracking

Term ” Intergranular liquid firm ”  —> Hot crack

Lamellar tearing

# Lamination (manufacture) vs Lamellar tearing (welding)

“Step like” appearance

Location just below the HAZ & Through thickness direction

The thicker the higher lamellar tearing susceptibility 

Weld decay ~ Inter-granular corrosion

• Because of Chrom-carbide (form at 650-800*C) at grain boundary (HAZ area)

Ti/Nb – Stabilizer (avoid forming Chrom-carbide) – Grade 321/347/348