From January 2020 post: NOTE: These are tips and guidelines/suggestions, acquired over the years. Not instructions.
There are steel grades (Mild Steel) that pretty much won’t harden by heat treatment. There are steel grades that are hardenable by thermal treatment. And there are steel grades that won’t harden during heat treatment but will harden if you whack em’ around; known as Work Hardening, Strain Hardening, or Cold Working steels. The most common of the work hardening grades (Austenitic) are the stainless grades 304L or 316L. They belong to a group of steel, categorized by grain type, as the austenitic stainless grades (typically 300 series, and the less common 200 series).
However, there is a non-stainless alloy steel that also work hardens; Hadfield Manganese Steel (or 11 to 14% Manganese, Austenitic Manganese Steel, or simply Manganese). It is a somewhat unique product that has found a home in heavy industrial applications where a combination of impact and abrasion tear up perfectly good steel. The railroad industry and the shot-blast industry are two of the prime venues for this product. As good as Manganese is in brutal service, it can also be somewhat “user adverse”; difficult to fabricate pretty much in every operation you might consider. It wants to work harden. During machining, it will harden ahead of your tooling, it will harden in the forming process, and it will be unforgiving of any misadventures in the welding process. Lack of attention to some simple details during welding, and you will be rewarded with embrittlement and fracture.
WELDING MANGANESE STEEL is not exotic or complex. The steel is just big and ugly, has a hard time making friends, and you need to respect some simple precautions. Think of everything you know about welding hard alloys, and pretty much reverse most of it. Don’t preheat Manganese Steel. Keep it cool, keep the interpass temp cool. Assist the welded unit to cool quickly; even if you have to spray some water to cool it. Employ techniques that tend to minimize welding temperature i.e short arc, minimize puddling, skip and backstep.
Don’t use carbon or low-alloy rods. Use Manganese Electrodes
If welding Manganese to Manganese:
Use Covered Electrodes (AWS A5.13, EFeMn-A) E-FeMnA
If welding Manganese to carbon or alloy
Use Covered Stainless Electrodes (AWS A5.4, E309) E-FeMn B
Use High Speed GMAW and FCAW not SMAW
If the Manganese has work-hardened in service (such as may likely be encountered in repair jobs),
cut away the hardened surface. Then apply a “butter-coat” of 307 stainless. The hardened surface, if not removed, will contribute to embrittlement and eventual fracture at the welded area.
Peen the welds while hot
Arc Welding is Good Don’t use OxyAcetylene (contributes to embrittlement)
Lean rod into direction of travel – flow the bead, don’t push it
Minimize energy input (65,000 joules max).
So, when welding hardened alloy steel, you are trying to get sound welds and maintain the hardness.
When welding Manganese, you’re trying to get sound welds period. Not protect any pre- hardened condition. Hardness will occur (or reoccur) when placed or placed back into service.
-Howard Thomas, December 7th 2021
