Alloys for Cast Iron

To successfully weld cast iron it is necessary to consider both welding techniques and the characteristics of the material. It is also necessary to investigate the reason for the damage and to take into account the requirements of the finished piece.
Types of Cast Iron
Gray cast iron is usually identified according to its tensile strength. 30 grade cast iron has a tensile strength of 30,000 psi; 40 grade cast iron has a tensile strength of 40,000 psi; and 60 grade cast iron has a tensile strength of 60,000 psi. The most common grades of cast irons are the 20 and 40 grades. Gray cast iron is a ferrous material containing more than 1.75% of carbon, the greater part of which is present in the structure in the form of graphite. This graphite gives to the fracture a color varying from light to dark gray. Compared with steel, gray cast iron has low malleability or ductility caused by the separation of the major portion of the elementary carbon in the form of graphite, which form a network throughout the metallic matrix and separate from it.
The chemical composition of a common machine casting is as follows:
                                                        Carbon 3.0% to 4.2%
                                                        Silicon 1.5% to 2.5%
                                                        Manganese 0.6% to 1.2%
                                                        Phosphorus 0.4% to 0.6%
                                                        Sulphur 0.05% to 0.18%

Basically, cast iron is steel with a lot more carbon. Steel contains carbon up to 1.75%. If steel has more than 1.75% carbon, it is called cast iron. Steel can dissolve up to 1.75% carbon. If more carbon is added, it won’t dissolve and remains a free carbon. When you look at cast iron under a microscope the free carbon appears as black flakes, hence the name “gray cast iron.” With the use of proper techniques and the correct filler alloy, most gray cast irons can be successfully welded.Be aware that there is another type of cast iron, called “white” or “chilled” cast iron. It is generally considered not weldable. White cast iron does not have the distinctive gray color of most cast iron and is generally found in equipment where extreme hardness is needed (e.g. rock crushers, steel mill rollers, etc.).

 

 
 
MG 200

• Premium high nickel alloy for cast iron.
• Maximum machinability of deposit and heat affected zone.
• Pulsating arc for low temperature welding of cast iron in all positions.
• Pulsating arc removes impurities resulting in a porosity-free weld deposit.
• For uses such as: engine blocks, gear-housings, joining cast iron to steel, and joining cast iron to stainless steels.

 

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MG 200 TIG

• Same characteristics as the MG 200, but in a 36” cut length TIG rod.

 

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MG 200 MIG

• Same characteristics as the MG 200, but in spooled MIG wire.

 

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MG 210

• Maximum strength alloy for cast iron.
• Special bi-metal core wire prevents overheating of electrode.
• Soft arc allows for easy machinability of highly crack-resistant weld deposit.
• Pulsating arc on DC-removes impurities from base material, even on dirty, oily surfaces.
• Suitable for welding cast iron to steel.
• For uses such as: cylinder heads, filing holes, machine bases, cast gear teeth, ship engine manifolds, and pump housings.

 

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MG 220

• Nickel free electrode with non-machinable deposit.
• Formulated for dirty and difficult-to-weld cast iron.
• Suitable for joining problem cast iron to steel.
• Successful when nickel alloys fail to adhere.
• For uses such as: burned furnace grates, build-up of abrasion worn areas, cracked machine bases, pump housings, and low quality cast iron.

 

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MG 240

• Bare cast iron gas rod for hot-welding.
• Excellent color match for gray cast iron.
• Designed for torch welding heavy and light castings.
• For uses such as: casting defects, gear-housings, cylinder heads, and engine blocks.
• Requires MG 240 Flux.

 

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MG 250

• High Nickel electrode for welding cast iron.
• Easily machined weld deposits.
• Welds are easily produced in all positions.
• Used to join gray cast irons to cast iron or to other ferrous materials.
• For uses such as: machine bases, machine handles, light & medium sized clean castings, and spot repair of cast iron.
• Meets AWS A5.15 E Ni-CI

 

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MG 260

• Nickel-iron electrode for welding gray and nodular cast iron.
• Machinable deposits.
• More resistant to abrasion than high-nickel deposits.
• Used where high strength and ductility is needed.
• For uses such as: heavy sections of cast iron, high nickel alloy, cast iron and nodular iron.
• Meets AWS A5.15 E NiFe-CI

 

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MG 262

• Premium cast iron electrode for joining and multi-layer build-up welds.
• Special bi-metal core wire prevents overheating of electrode and minimizes stub loss.
• High tensile strength and ductility. Good machinability.
• For uses such as: foundry cast, ductile foundry cast, GM 241 die build-up, heavy wall cast iron, joining cast iron, and cast steel.

 

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MG 289

• High strength alloy for dirty cast iron.
• Machinable deposits.
• Specially designed for contaminated, oil soaked cast iron.
• Alloyed core wire with unique flux coating produces strong,crack-resistant welds.
• For uses such as: joining cast iron to steel, transmission gear housings, gray, ductile, nodular cast iron, and sewer pipes.

 

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MG 289 W

• Gas shielded, high-strength, metal-cored wire for cast iron.
• Machinable deposits.
• Single or multi-pass.
• Flat or horizontal welds.

 

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