Wrought Iron Bridge Repair by Welding

[Rich2001]

I am developing a set or WPS for repairing a wrought iron bridge circa 1880; these procedures must be submitted for approval. I am very concerned about the potential liability and will include a comment, such as below on each WPS. I am looking from comments and guidance from this esteem group.

Base metals are what they are. Wrought Iron circa 1880.

The bridge will be painted so I am not concerned with galvanic corrosion as is typically the case with wrought iron repairs.

[maroon]
Wrought iron is a ductile, tough, fibrous, ferrous material composed of relatively pure iron and silicates, Iron Silicates (Fayalite), Magnesium Silicates (Fosterite) and Iron-Magnesium Silicates (Olivine). These silicates, commonly referred to as slag, are distributed throughout the pure iron in the form of threads or fibers that extend in the rolling direction. The quality of the wrought iron varies because of the range of carbon, manganese, phosphorus, sulfur and silicon that constitutes each individual member. (Sulfur tends to develop hot shortness at elevated temperatures, causing problems during weld repairs. Phosphorous leads to cold shortness, a brittle characteristic at room temperatures or lower). The wrought iron used in the original construction of this bridge has several shortcomings that are a result of a high percentage of phosphorus and sulfur and the directionality of the slag deposition. The slag content may vary and be in excess of 6% by weight. During welding the silicates will start to melt at approximately 1200ºC, this is below the liquidus temperature of the E7018 electrode of approximately 1600ºC. At high slag concentration, the slag may inundate the weld interface surface, resulting in poor fusion, porosity and inclusions. During the welding process the welder shall examine the weld puddle for any signs of excessive slag contamination such as bubbling. If excessive slag contamination is noticed the weld shall be removed my grinding and rewelded.

Ipso facto any repairs by welding shall only be considered as cosmetic, sans any increase in strength, or toughness and with a significant decrease in ductility and possibly a decrease in strength and toughness.

Only full penetration welds are allowed. Fillet and surface type welds typically will peal off wrought iron taking a thin layer of wrought iron at a slag–iron interface.

[/maroon]

Comments?


Vita sine litteris mors est.

 

[jheidt2543]

So, why allow the welding? Find an alternative repair to the welding. I was always under the impression (and by your note, you must be too) that welding of wrought iron is not advisable.

 

[Rich2001]

Many pieces are being replaced with ASTM A572 Gr 50 Steel. These weld procecedures are for items such as 50mm x 50mm x 6mm (2x2x0.25) angles that have a bent leg that is cracked along the slag thread.

Vita sine litteris mors est.

 

[stanweld]

I assume that someone in his/her ignorance has specified/proposed welding repair in lieu of mechanical repair methods. You should even more forcefully persuade the Owner/Engineer of his folly. I would futher my caveat and state that the Owner/Engineer will bear all responsibility for any liability due to failure of repairs in service and that your company will not warrant the repair; stating that the repair is made under duress. I would check it with Legal for their input prior to issuing the abvove to the Owner/Engineer before contemplating and proceeding with the repair.

 

[metengr]

NDT of the repair welds as final acceptance by the Owner - using Liquid PT or WFMT.

 

[EdStainless]

You can't be too cautious. Often WI failures are due to inclusions. Trying to weld repair these is like trying to repair stress cracking, it is a loosing propsition.
Mechanical repair is better. Add reinforcement, bracing or backing and join by bolts or rivets.
We repaired some overhead steel work in an old plant. After a few trys welding we gave up and did it all mechanical.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[UcfSE]

The last sentence of your first paragraph should say " 'by' grinding and rewelded.", not "my". I don't know if you just typed that in the window or copied and pasted. Spell check won't find it.

 

[Rich2001]

Thanks

Vita sine litteris mors est.

 

[jheidt2543]

Well, I looked a little closer:

REFERENCE: Kidder Parker Architects' and Builders' Handbook
Edited by Frank E. Kidder and Harry Parker
18th Edition, John Wiley & Sons, Inc., 1936

Page 412:
"Welds: Wrought iron is more easily welded than steel because the work may be accomplished through a wider range of temperature than with steel. A weld may develop the full strength of the bar, but tests on hand-forged welds on rough tie-bars reported by Kirkaldy gave average values of about 60% of the strength of the bar."

So, while wrought iron may be easy to weld, there seems to be a significant drop in the strength. I would think alternative repairs would give better and safer results.

 

[Carburize]

I think the reference in Kidder Parker Architects' and Builders' Handbook concerns forge welding - fusion welding is a much different proposition.

 

[btrueblood]

Also, in the final sentence - "peal" is what a bell does, "peel" makes more sense there to me.

 

[unclesyd]

Here is the an AISC reference to field welding of structures. It has been several years since I look at the article but as I remember it the recommendation is the same as the consensus of the current respondents.

“Field Welding to Existing Steel Structures” Ricker

http://www.aisc.org/Template.cfm?Se...e=/Ecommerce/ProductDisplay.cfm&ProductID=768

 

[teb1]

Rich2001,

Please refer to this thread thread 181-27567

Thanks,

teb1

 

[Rich2001]

thread181-25767 ?

Vita sine litteris mors est.

 

[teb1]

It has the name of a company and a procedure that might be of benefit to you in this cast iron repair project.

Teb1

 

[Rich2001]

What is the title of thread181-27567 ?

The 181 designenates the "CSI (construction) Code Issues Forum."

Vita sine litteris mors est.

 

[teb1]

Sorry 'bout that. Try the thread listed below with regard to a cast iron turbine case repair.

thread725-116788