welding expertise

Maintenance welding

Majority of industrial sectors: power,transportation,construction,piping,defence,aero space,castings,forgings and general fabrication are involved in maintenance welding.Thorough knowledge helps to successfully complete given task.

fig 1. Forging repair :Metal to metal wear

Hardfacing for better maintenance welding

http://www.aws.org

Hard-facing  protects parts against wear and ensures certain specific wear resistance or properties.

https://youtu.be/9R_pzbIGfJI

• Welding processes
  The most common processes  are:
  Shielded Metal Arc Welding, SMAW
  Also known as Manual Metal Arc Welding (MMA)
  • covers the widest range of weld metals
  • is inexpensive
  • is a versatile process used outdoors and for out-of-position work.   https://youtu.be/xL0nvZ1F47Q
• Flux-Cored Arc Welding, FCAW
  • alloy availability almost the same as covered electrodes • high deposition rate
  • can be used on site due to open arc operation
  • self-shielding, no extra gas is needed
  Submerged Arc Welding, SAW
  • limited range of products
  • high deposition rate – to rebuild large worn parts • no arc flash or spatter
• Gas welding also continues to be used for some applications.
• Wear factors
  A large number of different wear factors exist. Consequently,  weld metals must be used with caution to meet specific use.
  For example; when examining a part, it is determined that the primary wear factor is abrasion and the second is moderate impact. The hard-facing alloy should have very good abrasion resistance but also reasonable impact resistance.
• Wear from metal parts such as shafts against bearing surfaces, chain links against a roll, sprockets, steel mill rolls require
  Martensitic hard-facing alloys ,
  Austenitic-manganese and cobalt alloys are also good ,
  Cobalt alloys are used in high-temperature and oxidation environments.
• contact between  materials of the same hardness ,result in excessive wear.

Classification of weld metals.

iron-based:
• martensitic alloys • austenitic alloys
• carbide-rich alloys
non-iron-based:
• cobalt-based alloys • nickel-based alloys
For wear applications.
martensitic:
Both for building up and surfacing: • good metal-to-metal resistance
• good impact resistance
• fair abrasion resistance
austenitic:
• excellent impact resistance • good build-up alloy
• fair abrasion resistance
carbide-rich:
• excellent abrasion resistance • good heat resistance
• fair corrosion resistance
• poor impact resistance
cobalt- & nickel-based
Most types of wear, but, due to their higher cost, they are mainly used in applications in which their properties can be economically justi- fied, such as high-temperature applications in which carbide-rich, iron-based alloys have a low resistance. Nickel alloys are the cheaper alternative