Hand welding practice problem - Edwards @ Wiki

1 General knowledge of coated arc welding

Question 1.1 Advantages of welding commentary

1. The welded joint has high strength against other joining methods
2. Residual stress arises at other parts due to metal contraction accompanying welding
3. Work man-hours and work cost are reduced
4. Product weight is lightweight

Question 1.2 Disadvantages of welding commentary

1. Deformation and distortion occurred
2. Attract destruction by welding residual stress
3. Weld heat effect occurs
4. Work man-hours reduced

Question 1.3 Welding method commentary

1. Submerged arc welding of automatic arc welding is highly efficient by full automatic welding
2. Spot welding is frequently used for thin plates / confidential performance is inferior
3. TIG welding is frequently used for stainless steel and aluminum alloy
4. MAG welding is frequently used for mild steel

Question 1.4 Welding method

1. Covering of the coated arc welding rod prevents oxidation
   and nitriding of welded parts and achieves stable arc
2. TIG welding prevents argon from oxidizing or nitriding welded parts
3. Gas welding prevents oxidation and nitridation by flux
4. Mixed gas of CO_{2} or Ar + CO_{2} is used in MAG welding

Question 1.5 Classification of welding method: Joining

1. Fusion welding: Coated arc welding
2. Fusion welding: laser beam welding
3. Brazing: Silver brazing
4. Press welding: Spot welding

Question 1.6 Classification of welding method: Used substance

1. MIG welding: Ar
2. Coated arc welding: acetylene
3. Covered arc welding: Coated arc welding rod
4. Coated arc welding / semi-automatic welding / gas welding: flux

• Flux / coating material: effects on each welding intervening medium
  • Arc gas discharge phenomenon stabilized
  • Protect molten metal from oxidation
  • Improve weld strength

Question 1.7 Proper Welding Method

1. TIG / MIG welding: Aluminum alloy application
2. Submerged welding: High efficiency
3. O_ {2} / acetylene welding: mainly mainly welding cut
4. MAG welding: Frequently used for welding mild steel

Question 1.8 Welding terms

1. Heat-affected zone: For thermal influences in each welding process, etc.,
   the property changing portion except the fusion-bonded portion
2. Surplus: Weld surplus part to weld surface
3. Penetration: Distance between the melted part of the base metal and the welded melted part
4. Penetrating defect: Spatial generation for complete penetration welded joint

Question 1.9 Welding terms: Weld state

1. Heat-affected zone: For thermal influences in each welding process, etc.,
   the property changing portion except the fusion-bonded portion
2. Surplus: Weld surplus part to weld surface
3. Penetration: Distance between the melted part of the base metal
   & the welded melted part
4. Penetration defect: generation space for complete penetration welded joint
   
   1. Complete penetration: penetration to the back side of welding target
   2. Partial penetration: penetration into the welding target

• Welding terms: Various defects
  • Weld defect: Spatial occurrence state between multilayer fusion welding
  • Fusion defect: state of melting failure in backing metal of butt joint
  • Undercut: the state of occurrence of the gap
    between the bead and the base metal on the welding surface
  • Overlap: Surface deposition state of weld metal in left-right direction
    of bead progress between weld metal base materials

Question 1.10 Measures to prevent chemical change in welding

1. Manual welding: commonly coated arc welding
2. MIG welding: Ar gas is frequently used as a shielding gas
3. MAG welding: frequently used for semiautomatic welding
4. Gas welding: Formation of heat source by acetylene and O_ {2}

Question 1.11 Measures against oxidation and nitriding of molten metal

1. Manual welding: Welding rod is covered with covering material
   for core wire to prevent chemical change
2. MAG welding: using mixed gas such as CO_ {2} or Ar + CO_ {2}
3. TIG welding: using Ar gas
4. Submerged arc welding: Using granular flux

Question 1.12 Welding defect

1. Penetration defect: generation of space for complete penetration welded joint
2. Fusion failure: Mutual connection defect between weld metal and base metal at weld boundary
3. Undercut: generation of grooves relative
   to the weld bead toe and the surface between the base metal
4. Overlap: The state of weld bead deposits on the surface of the base metal

Question 1.13 Welding method overview

1. TIG welding: In conjunction with the arc generation between the tungsten electrode and the base metal,
   Ar is released and welding is performed using a welding rod
2. MIG welding: The wire is fed to the welding part,
   Ar is released between the base materials as the arc is generated, welding
3. Self-shielded arc welding: A flux-cored wire is fed to the welded portion,
   an arc is generated by welding power between the base metal and welded
   Note:No wind measure required
4. Submerged arc welding: Particulate flux is scattered on the welded part
   and welded by inserting the electrode wire

Question 1.14 Difference between fusion welding and insulation displacement

1. Fusion welding: melting medium is supplied and joined by melting and solidification
2. Press welding: Heat the objects to be joined to the surrounding environment of melting and join by pressure
   1. Cold pressure welding: Heating the medium mutually and joining by pressure
   2. Hot welding: Heating up the medium to the melting temperature and bonding by pressure

Question 1.15 Types of pressure welding method

1. Fusion welding: joining objects to be joined by melting
   1. Resistance welding (spot welding): Along with proper pressurizing force,
      current is allowed to flow together,
      melted and adhered to each other by heat generated by the contact resistance of the joint
   2. Gas pressure welding: Mixed atoms are joined together
      by appropriate cooling time together with the pressure and heating of the joint surfaces
   3. Forge welding: Forge joint materials are applied to the joint surfaces
      and joined by applying pressure together with heating

Question 1.16 Difference between welding and mechanical connection such as bolt

1. High Strength
2. lightweight
3. Reduction of construction period

Question 1.17 Disadvantages of fusion welding

1. Residual stress: caused by expansion and contraction of joint
2. Deformation: caused by the difference between thermal expansion
   and cooling contraction of each joint
3. Material change: base metal properties changed by weld metal heat source

Question 1.18 Causes of thermal deformation

1. Disturbance of heat accumulation at the welded part and the adjacent part
2. Residual stress accompanying contraction of welded portion