Welding-cast-iron,

for repair or fabrication.

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Welding-cast-iron is the subject of this page.

What is in here for me?

What benefits can be found here? Essentially a short overview of problems concerning Welding-cast-iron.

However as types and conditions of various cast irons can be very different, so could be the problems and the answers.

For any questions on these subjects, write us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.


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Welding cast iron is mainly used for repairing casting defects in the foundry, followed by salvaging of worn or broken castings in service, and finally for fabrication of welded assemblies.


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Metallurgical Expertise.

Welding-cast-iron deals with classes known as Gray, Malleable and Nodular (or Ductile) according to typical appearance of their microstructure, which affects their properties.

Cast irons are alloys of iron, carbon and silicon (may have over 2% carbon and 1-3% silicon), and may include specific amounts of other elements to achieve definite characteristics.

Properties of Cast Iron

The properties sought for when selecting cast iron are usually economy, good castability even in complex forms, damping of vibrations, resistance to heat checking or heat shock, although strength may not be the primary consideration.

Common applications examples are housings, enclosures, machine frames and bases, pipe fittings, clutch plates, brake drums, counterweights etc.

Problems with Welding-cast-iron

Are there problems in Welding-cast-iron? Cast iron is much less weldable than low carbon steel because it contains much more carbon and silicon, it is brittle and it tends to crack.

A ductile material should be chosen as filler metal.

Specially formulated cast iron electrodes are available.

However, fillers based on nickel or bronze, although more expensive, are sometimes preferred for their increased ductility.

If the weld has to be machined, regular filler metal for cast iron may result too hard.

Selecting a filler metal as above, more ductile and more expensive, may solve the machinability concerns.

In case of repair welding, one should know before Welding-cast-iron what are material and condition of the job at hand.

It is common practice to apply preheating to castings and to provide protected slow cooling, with the purpose of reducing residual stresses and of avoiding cracking.

Preheating (that is heating the part before welding) slows the cooling rate after welding, permitting the formation of less brittle structures.

It also permits to the whole casting to contract together with the weld material, reducing residual stresses due to differential thermal gradients.

Welding-cast-iron for repair may be prohibited in certain highly stressed areas of castings where welding failure is not acceptable.

Welding-cast-iron on surfaces to be machined is permitted, if machining is possible at all. However requirements are set by the user who may or may not allow repairs in specific areas.

In any case edge preparation or area preparation for Welding-cast-iron is most important. it should ensure complete removal of defects and provide room for satisfactory filler metal deposition with the minimum penetration allowed.

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Arc Welding is widely used for Welding-cast-iron. The most popular manual process employed is probably Shielded Metal Arc Welding (SMAW), with proper procedures involving preheat and postheat. One commonly uses nickel based, nickel-copper (Monel) or other bronze electrodes.

Nickel electrodes and Cast iron electrodes and rods are classified in the following:

  • ANSI/AWS A5.11/A5.11M:2010
    Specification for Nickel and Nickel Alloy Welding Electrodes for Shielded Metal Arc Welding
    Edition: 10th
    American Welding Society / 15-Dec-2009 / 52 pages

  • ANSI/AWS A5.15-90 (R 2006)
    Specification for Welding Electrodes and Rods for Cast Iron
    American Welding Society, 01-Jan-1990, 10 pages

Tip!: it is advisable to follow recommendations as published by established suppliers, for Welding-cast-iron. A few tests should always be conducted before selecting a definite product for a repetitive job, in order to find the best solution for the given application under the prevailing circumstances, including welder's skill.

Gas Tungsten Arc Welding can be used for Welding-cast-iron (gray iron). A higher preheat is usually recommended. Filler materials in form of rods but of chemical composition similar to those used for SMAW can be used. Also austenitic stainless streels have been used with direct current, straight polarity (electrode negative). Preheat temperature is usually higher. GTAW does not present any significant advantage vs. other less expensive processes.

Gas Metal Arc Welding is better suited to Welding-cast-iron of Ductile and Malleable Iron types than for Gray Iron. It is however used when productivity gains are important.

Manual Gas Welding or more properly oxyacetylene welding, is performed regularly with success for Welding-cast-iron in small castings.

The characteristics of the flame can be controlled to be neutral, carburizing or reducing, as better adapted to the work on hand, but in any case the flame and its surrounding atmosphere can effectively protect the workpiece and the tip of filler metal, if used, from contamination from air.

The Oxyacetylene Process can be used for Welding-cast-iron, generally for repair or modifications. One must use appropriate fluxes and suitable filler material like cast iron or bronze, if the difference in color is not objectionable for the application.

This process is performed at lower temperatures but with higher heat input than arc welding and is usually slower. It is used with preheat and postheat treatments, and may develop less hard and brittle heat affected zone, which may be an advantage.

Oxyacetylene welding is generally applied for Welding-cast-iron Gray and Ductile. It is not recommended for Malleable iron because it is likely to produce a wide heat affected zone of hard and brittle white iron.

Braze-Welding can be performed instead of Welding-cast-iron, with proper filler metal, exploiting the advantage of using lower temperature copper based filler rods (bronzes) and a proper flux. To see a page on this process click on Braze Welding. The main objection may be that the weld will stand out because of the different color.

UPDATED PAGE

See the updated page now including a description of suggested Oxyacetylene Welding and Cutting outfits suitable for a wide range of practical welding, brazing, braze-welding and cutting needs.
Click on Gas Welding Equipment.

Any questions on Welding-cast-iron or comments or feedback? Write them down and send them to us by e-mail. Click on the Contact Us button in the NavBar at top left of every page.

An Article on Filler Metals for Welding-cast-iron was published in the April 2004 issue of Practical Welding Letter.
To read the Article click on PWL#008.

An Article on Welding-cast-iron to Mild Steel was published in the Issue 25 of September 2005 of Practical Welding Letter.
To read the article Click on PWL#025.

An Article on Welding Cast Iron to Alloy Steel was published (4) in Issue 89 of Practical Welding Letter for January 2011.
Click on PWL#089 to see it.

An Article on Filler Metal for a Combustion Chamber (dealing with welding a Cast Iron inlet fitting, placed in a cooler area, to a 310 stainless Combustion Chamber) was published (4) in Issue 130 of Practical Welding Letter for June 2014.
Click on PWL#130 to see it.

A new page is available on Casting-Repair.
Click on the link to open it in a new page.

A Bulletin with online Resources on Weld Repair of Castings was recently published. Click on Bulletin 105 to see it.

A Bulletin with online Resources on Cast Iron was recently introduced (8) in Issue 155 of Practical Welding Letter for July 2016.
Click on PWL#155.

To receive regularly the Letter as it is published please subscribe.

Unsuitable processes...

Welding-cast-iron is not suitable by Friction Welding, a solid state process with lower than melting temperature, because cast iron contains graphite which interferes with heating and because the material is not forgeable, which is a pre-condition for the process.

Also Resistance Welding Process is not applicable to Welding-cast-iron.

Repairing a crack in Cast Iron

The following Section summarizes the information needed to repair, by Welding-cast-iron, a crack found in a Cast Iron body. It is the result of recurring requests on the part of our readers who asked for detailed answers to their problems.

We deal primarily with Gray Cast Iron which represents the largest majority of general purpose castings. Other types of cast iron include Nodular (or Ductile), and Malleable Cast Iron, which were developed to provide more elaborated mechanical properties, suitable for specific purposes.

Disclaimer

Please be advised that our presentation hereafter deals only with the most common class of gray cast iron where no special requirements are demanded from the material. In case of doubt readers are urged to investigate if their application is more specialized and then they should seek specific advice for action.

Preparation

It is understood that for Welding-cast-iron a cracked item it should be stripped of any accessories and parts assembled to it, and freed of any external loads.

Assuming that the crack is limited in size, and the part is not broken in two or more separate pieces, one needs to drill a small stop hole (about 3 mm or 1/8") at each end of the crack and its branches. To find the end one should grind the area with sandpaper and look with a magnifying glass.

Then the crack has to be cleaned by mechanical means like milling or hand grinding with a proper grinding wheel, to provide a V shape channel, with an opening of 60 degrees reaching the bottom of the crack, usually leaving a thin "land" to be completely melted during Welding-cast-iron. In thin sections, backing may be required to get a full penetration root pass. Thicker walls may need special shape channels.

Completes the preparation a thorough cleaning of the area, especially if the casting is soaked with oil, grease, paint or other contaminants. A burnout should be done in a furnace for 15 minutes at 480 °C (900 °F), followed by energetic brushing to remove residues.

Preheating

Reasons for preheating for Welding-cast-iron were already pointed out in this page and in our Weld Preheating Page. Preheating should be performed in a furnace at 200 to 300 °C (400 to 600 °F) for at least an hour. For a small casting torch heating may be acceptable.

Welding

Shielded Metal Arc Welding (SMAW or stick) with covered electrodes is the most applied process. Filler metal available ranges from electrodes for cast iron (designated ECI) to Nickel containing electrodes (ENi-CI,
ENiFe-CI [preferred for general purposes], ENiCu-A, ENiCu-B) and other types, including bronzes.

The selection should be based essentially on experience, preferring the most economic material that permits welding without producing other cracks. For one occasional repair it is suggested that the Nickel electrodes be used, although more expensive, because they are more ductile and as such capable of absorbing larger stresses without cracking.

The technique should concentrate in melting the minimum of base metal, by introducing the least amount of heat, with the smallest electrode at the least current, with thin weld beads. The weld is built up with additional beads (after slag removal) until finished, without cooling down.

Post heating

The welded part should then be allowed to cool down slowly under covering of insulating material or, preferably, be stress relieved immediately in a furnace at 600 to 650 °C (1100 to 1200 °F) for one hour and then furnace cooled.

Other processes

Oxyacetylene Welding is also possible, with the same preparation, but then, with proper filler metal, Braze-Welding can be performed instead, as per above reference.

Accepted ASTM Specifications on Cast Iron are listed hereafter (please check to confirm the last edition):

ASTM A47/A47M-99(2009)
Standard Specification for Ferritic Malleable Iron Castings
ASTM International / 01-May-2009 / 5 pages

ASTM A48/A48M-03(2012)
Standard Specification for Gray Iron Castings
ASTM International / 01-Oct-2012 / 6 pages

ASTM A74-09
Standard Specification for Cast Iron Soil Pipe and Fittings
ASTM International / 01-Jan-2009 / 44 pages

ASTM A126-04(2009)
Standard Specification for Gray Iron Castings for Valves, Flanges, and Pipe Fittings
ASTM International / 01-Oct-2009 / 3 pages

ASTM A159-83(2011)
Standard Specification for Automotive Gray Iron Castings
ASTM International / 01-Mar-2011 / 5 pages

ASTM A247-10
Standard Test Method for Evaluating the Microstructure of Graphite in Iron Castings
ASTM International / 01-Mar-2010 / 2 pages

ASTM A278/A278M-01(2011)
Standard Specification for Gray Iron Castings for Pressure-Containing Parts for Temperatures Up to 650 °F (350 °C)
ASTM International / 01-Mar-2011 / 4 pages

ASTM A319-71(2011)
Standard Specification for Gray Iron Castings for Elevated Temperatures for Non-Pressure Containing Parts
ASTM International / 01-Mar-2011 / 2 pages

ASTM A327/A327M-11
Standard Test Methods for Impact Testing of Cast Irons
ASTM International / 15-Oct-2011 / 4 pages

ASTM A 339 - Discontinued

ASTM A395/A395M-99(2009)
Standard Specification for Ferritic Ductile Iron Pressure-Retaining Castings for Use at Elevated Temperatures
ASTM International / 01-May-2009 / 8 pages

ASTM A 396 - Discontinued

ASTM A436-84(2011)
Standard Specification for Austenitic Gray Iron Castings
ASTM International / 01-Mar-2011 / 6 pages

ASTM A438 - Withdrawn

ASTM A439-83(2009)
Standard Specification for Austenitic Ductile Iron Castings
ASTM International / 01-May-2009 / 6 pages

ASTM A476/A476M-00(2009)
Standard Specification for Ductile Iron Castings for Paper Mill Dryer Rolls
ASTM International / 01-Oct-2009 / 5 pages

ASTM A518/A518M-99(2012)
Standard Specification for Corrosion-Resistant High-Silicon Iron Castings
ASTM International / 01-Oct-2012 / 5 pages

ASTM A532/A532M-10
Standard Specification for Abrasion-Resistant Cast Irons
ASTM International / 01-Apr-2010 / 4 pages

ASTM A536-84(2009)
Standard Specification for Ductile Iron Castings
ASTM International / 01-May-2009 / 5 pages

ASTM A571/A571M-01(2011)
Standard Specification for Austenitic Ductile Iron Castings for Pressure-Containing Parts Suitable for Low-Temperature Service
ASTM International / 01-Mar-2011 / 5 pages

ASTM A602-94(2009)
Standard Specification for Automotive Malleable Iron Castings
ASTM International / 01-May-2009 / 5 pages

ASTM A608/A608M-12
Standard Specification for Centrifugally Cast Iron-Chromium-Nickel High-Alloy Tubing for Pressure Application at High Temperatures
ASTM International / 01-Sep-2012 / 6 pages

ASTM A644-09a
Standard Terminology Relating to Iron Castings
ASTM International / 01-Jul-2009 / 4 pages

ASTM A667/A667M-87(2012)
Standard Specification for Centrifugally Cast Dual Metal (Gray and White Cast Iron) Cylinders
ASTM International / 01-Oct-2012 / 2 pages

ASTM A748/A748M-87(2012)
Standard Specification for Statically Cast Chilled White Iron-Gray Iron Dual Metal Rolls for Pressure Vessel Use
ASTM International / 01-Oct-2012 / 2 pages

ASTM A823-99(2012)
Standard Specification for Statically Cast Permanent Mold Gray Iron Castings
ASTM International / 01-Oct-2012 / 7 pages

ASTM A834-95(2011)
Standard Specification for Common Requirements for Iron Castings for General Industrial Use
ASTM International / 01-Mar-2011 / 4 pages

ASTM A842-11a
Standard Specification for Compacted Graphite Iron Castings
ASTM International / 01-May-2011 / 5 pages

ASTM A874/A874M-98(2009)
Standard Specification for Ferritic Ductile Iron Castings Suitable for Low-Temperature Service
ASTM International / 01-May-2009 / 3 pages

ASTM A888-11
Standard Specification for Hubless Cast Iron Soil Pipe and Fittings for Sanitary and Storm Drain, Waste, and Vent Piping Applications
ASTM International / 15-Jun-2011 / 58 pages

ASTM A897/A897M-06(2011)
Standard Specification for Austempered Ductile Iron Castings
ASTM International / 01-Nov-2011 / 9 pages

ASTM A942-95(2012)
Standard Specification for Centrifugally Cast White Iron/Gray Iron Dual Metal Abrasion-Resistant Roll Shells
ASTM International / 01-Oct-2012 / 2 pages

NEW RESOURCES

Find some interesting links in a special Mid Month Bulletin Page of our PRACTICAL WELDING LETTER, designed offer you, our interested readers, the opportunity to search the web quickly and effectively on the subject of welding Cast Iron.

We urge you to explore this rich source of essential knowledge.

Online Resources on Welding of Cast Irons, presenting Articles, Tables, Data, Properties, Specifications, Downloads, Links and Information is now available by clicking on PWL#045B.

Looking for more Online Reference Links? Click on Welding Resources

Watch the following Video:

Repairing a Crack in Cast Iron

Lincoln Electric Tech Tips.

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Hardness Testing
made simple Let us remind you that, if you are interested, we offer a no cost subscription to our Practical Welding Letter and a bonus book in pdf format to be made available for download to your computer on the subject of
PRACTICAL HARDNESS TESTING MADE SIMPLE.
Click on Subscription.

To reach a Guide to the collection of the most important Articles from Past Issues of Practical Welding Letter, click on Welding Topics.

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See how Welding-cast-iron for repair or fabrication is readily performed with due care to reduce brittle constituents and to avoid cracks. Special fillers and procedures are requested.