case hardened steal

By ironeagle93 Date 04-09-2008 14:41

a friend of mine is trying to mig-weld case hardened bed frame rails to non- case hardened angle iron to strengthen his trailer, and the welds crack when he tries to straighten them after they are welded, I think he is hitting them with a hammer. I told him to make sure the pieces are clean and free of paint, and to use a stick welder,(he has one of those small mig welders) , I also told him to increase the heat on the mig to get a larger weld to work with. Can you let me know if there is something else he should do. Thanks for any help you can give me.

By G.S.Crisi (****)

Date 04-09-2008 19:04

Case hardened steel is impossible to weld. Not surprise he's having trouble.
The material is too hard and contain too much carbon.
Giovanni S. Crisi
Sao Paulo - Brazil

By GRoberts (***)

Date 04-09-2008 19:11

If the rails are indeed case hardened, the carbon layer should only be on the surface. Once the case-hardened surface is removed, the weldability will only depend on the base metal used for the rails.

By G.S.Crisi (****)

Date 04-09-2008 21:26

Right, GRoberts. I would add that the thin hardened layer should be removed by means of a silicon carbide grinding wheel, which is harder than the layer.
Giovanni S. Crisi

By weiser1876 (*)

Date 04-10-2008 02:05

[deleted]

By G.S.Crisi (****)

Date 04-10-2008 19:56

Seems that there are two possibilities:
1. The frame is actually case hardened steel. If this is true, then in my opinion weiser's suggestion will not work, because the carbon content of the surface layer of case hardened steel could be as high as 1 - 1,2 %, and even if the steel has softened down, weld will be impossible.
2. Dave is right and the frame is just medium carbon steel. In this case, I agree with his suggestion.
Giovanni S. Crisi

By weiser1876 (*)

Date 04-11-2008 05:19

it may have worked as a back woods fix but after i wrote and thought about it bad advice sorry do it right or dont do it at all to many people on the roads to hurt or kill in some advice like that sorry I slaped my self use the bed rails for a bbq grill or fince post not bracing on a traler

By DaveBoyer (*****)

Date 04-10-2008 02:15

   Bed frame is not case hardened, it is medium carbon, and needs to be treated as such.

   Having said that, I have made a bunch of things from bed frame with a light industrial MIG using .035 70-S6 wire and C25 gas and had no problems. I think in My case there was enough residual heat that the bed frame was not brittle.

   Post heating and slower cooling should help, and Low Hydrogen rods and practices should help if stick welding.

   If I were strengtehing a trailer frame I would use structural low carbon steel and larger & heavier sections than bed frame.

Depending on how small His machine is, it might not be up to the task.

By weiser1876 (*)

Date 04-11-2008 05:12 Edited 04-11-2008 05:25

DaveBoyer is right use structural steel on it 2"X3"X3/16 is normal on trailers 2" top 3" down no more than 16" centers for the runers run them acrost the trailer not down the trailer good luck