For Cast Iron

Cast Iron Welding Consumables Introduction-Covered Electrodes

 1.Parent Material Properties:

  Cast Iron contains carbon (C): 2 ~ 4%、Si:0.5 ~ 4%、Mn:0.3 ~ 2%、P:0.05 ~ 1%; the iron-based alloy casting. It applies for a special purpose with additional content of Mn, Si, Ni, Cr or Mo alloys, but worse toughness and weldability. Common cast iron classification is shown in the table below

 

category

JIS Chapter

 JIS Code

Characteristics

Gray Cast Iron

General cast iron

G5501

FC100  FC150

FC200

①All purpose for industries, well-known named with broken surface in gray color.

②High-grade cast iron comprised of Pearlite structure; the higher strength and toughness than general cast iron.

High-grade cast iron

G5501

FC250  FC300

FC350

Nodular cast iron

Nodular cast iron

G5502

FCD350  FCD400

FCD450  FCD500

FCD600  FCD700

FCD800

①Also named ductile iron or nodular cast iron. Generally add Mg, Ce or Ca in the composition of the original spheroidizing graphite cast iron.

②Tensile strength is a 2-3 times of general cast iron; the higher elongation and well weldability.

Austempered Ductile Iron (ADI)

G5503

FCAD900  FCAD1000

FCAD1200

FCAD1400

Ferritic nodular cast iron

G5504

FCAD300LT

(Low temperature use)

Malleable Cast Iron

blackheart malleable cast iron

G5702

FCMB270  FCMB310

FCMB340  FCMB360

①Blackheart malleable cast iron is originally made of whiteheart malleable cast iron by heating at 700~900℃ to dissolve Cementite into graphitization so as to be capable of toughness in Ferrite with the black broken surface.

②Whiteheat malleable cast iron is to heat the white pig iron at 850-1000℃ into oxidizing phenomenon for decarbonization that improves thoughness.

③Pearlite malleable cast iron is formed into graphite and pearlite structure by heating process that performs better in cutting, wearing, strength, and quenching. cutting, wearing

whiteheart malleable cast iron

G5703

FCMW300  FCMW370

FCMWP440  FCMWP490

FCMWP540

Pearlite malleable cast iron

G5704

FCMP440  FCMP490

FCMP540  FCMP590

FCMP690

Alloy Cast Iron

Ni-alloy cast iron

--

--

Resistance of heat, corrosion, and wearing.

Cr-alloy cast iron

--

--

Hardening, wearing and heating resistances

Ni-Cr alooy cast iron

--

--

Alloy cast iron is the most use, high strength, toughness, hardness, heat and corrosion resistances.

Ni-Cr-Mo alloy cast iron

--

--

High strength, fatigue and wear resistances generally use for engine crankshaft.

Ni-Cr-Si alloy cast iron

--

--

Heat resistance generally use for stove metalware.

Ni-Cr-Cu alloy cast iron

--

--

Heat and acid resistance.

Al-alloy cast iron

--

--

Heat and acid resistance generally use for boiler accessories.

 

 

2.Welding method and characteristics:

It is due to the high content of carbon, poor weldability, and even to difficultly weld for cast iron alloy. The common problems on welding are cracking and blowholes, and therefore, should avoid to. 

①Hard and brittle white pig rod martensitic structure composition may cause cracking phenomenon.

②Cementite and graphite are both dissolved and oxidized after heating with high temperature that it causes with a large amount of CO or CO2 gas resulting in blowholes.

 

   In Cast iron welding process, the preheat temperature can be classified high-temp. and low-temp. on welding. High temperature preheat is at 500 ~ 600℃ in whole parent material and then welding afterwards. Generally, it applies for oxyacetylene welding or electrode welding; the large deformation of workpiece and longer waiting time of preheat as disadvantage. Low temperature preheat at the welding part is at 100 ~ 200℃ and then welding afterwards. It applies for electrode welding, argon welding or gas metal arc welding (GMAW); the smaller deformation of workpiece but the brittleness at HAZ.

 

In order to weld effective combined with parent material, cast iron workpiece on welding artwork the common applications are recommended as follows:

 

①Embedded board & Bar filling:

In order to increase the strength of the weld filling, the cast iron filling and welding parts embedded with steel material, steel bar as reinforcement; the recommended welding consumable of ENiFe-CI.

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Implant bolts

Implant bolts prior to welding; weld the bolts around to the entire weld.

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③Drilling cracking holes

 In order to prevent the cracks continuous and expanding, and therefore, it is required to drill a hole at each side of the crack and then wear it in an arc groove and fill it up.

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④Coating:

The cracking is usually caused near the melting interface and HAZ. Welding a dual coatings with Eni-Ci grade material at the groove surface and then fill it up afterwards for the welding difficulty on workpieces.

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⑤Hammering:

Repeatedly hammering on the deformed weld after welding is for the stress relief. The head of the hammer must be blunt head in order to prevent the stress concentration for cracks, but not recommended for the bottom weld or surface weld.

 

⑥Cracks on each side of spot welding:

Gray cast iron welding is to spot welding on each side of the crack by a short distance between so as to release the stress and then weld it; grinding the spot welding part off at the end.

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