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Metal materials and Welding materials

3 Iron and Steel Materials

3.1 Basic knowledge of steel materials -
      and coated arc welding rod due to hand arc welding

• Iron and Steel Materials summary
  • Mild Steel: Less carbon content and widely used
  • High tensile strength steel
  • Stainless steel
  • Heat resistant steel
  • Aluminum
  • Titanium

3.1.1 Iron & Steel

• The Iron
  Element Latin name "Fe"
  Properties of pure iron: Can not be used as structural material
  • Low Hardness
  • Low strength

• 5 elements of Steel
  • Additive element
    • Carbon: C
    • Manganese: Mn
    • Silicon: Si
  • Impurity element
    • Phosphorus: P
    • Sulfur: S

• Types of carbon content for steel
  • Steel: Contains about, to 2.00 [%] from 0.03 [%] carbon.
  • Cast iron: Contains about, to 4.50 [%] from 2.00 [%] carbon.

• Types of steel hardness for added elements
  • Steel tension steel classification
    Note: [N/mm^{2}] is "SI" formula
    • Tensile strength 490 [N/mm^{2}] grade: 50 [kgf/mm^{2}]
    • Tensile strength 590 [N/mm^{2}] grade: 60 [kgf/mm^{2}]
    • Tensile strength 780 [N/mm^{2}] grade: 80 [kgf/mm^{2}]
  • Additive Cr Ni Mo alloy classification
    Improved corrosion resistance, heat resistance, high temperature strength
    • Low Alloy Steel: Additive amount less than 10 [%]
      • 3.5 [%] Ni Steel
      • 9.0 [%] Ni Steel
    • High Alloy Steel: Additive amount 10 [%] or more
      • Stainless Steel: 18.0 [%] Cr+8.0 [%] Ni
        Note: SUS: Steel use stainless

• Additive element for purification
  • Deoxidizer
    • Mixing of Mn and Si promotes the formation of MnO and SiO_ {2} and reduces oxidation
  • Contaminating impurities
    • P and S mixed by smelting process
    • Generally reduced to less than 0.04 [%] in the smelting process

3.2 Material change of steel weld
3.2.1 Metallurgical change of weld zone

• Method for cooling heat treatment of carbon steel
  • Hardening
    Heat it to about 900 [^{\circ} C],
    settle down in water or oil and improve hardness by rapid cooling.
  • Tempering
    After Hardening, after heating at 723 [^ {\ circ} C] (A_ {1} point)
    Air cooling to reduce hardness and improve viscosity.
  • Annealing
    • High temperature annealing
      After heating to about 900 [^{\circ} C], gradually cooling in the furnace
      Improve viscosity by eliminating processed metal structure
  • Grilling
    Approximately 900 [^{\circ} C] air-cooled after heating,
    Smoothing of metallic structure changed by welding and others.

3.2.2 Omission

3.2.3 Welding heat input

• Increase of thermal energy amount to welding
  • Increase in welding current
  • Increase in arc voltage: fixed in actual welding machine
  • Weld heat input is inversely proportional to welding speed
    • H [J/cm]: welding heat input
    • I [A]: welding current
    • E [V]: arc voltage
    • k = 60 [sec]
    • v [cm / min]: welding speed
      H=\frac{k\times E\times I}{v}~[J/cm]