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  1. #1
    Join Date
    Sep 2006
    Location
    Milton Ontario
    Posts
    29

    Default Welding procedure for welding HT4140 to mild steel

    Anyone developed a welding procedure for welding HT4140 to mild steel? I need to fabricate a pair of spindles for a road race car and the pin we are using is 2" dia. HT4140, and the spindle uprights are mild steel.

  2. #2
    Join Date
    Jan 2009
    Location
    Cleveland, TN
    Posts
    229

    Default

    This is not a welding tip, but a press fit one. Most pins are machined to have a press fit. (about .003 in.) You put it in the freezer for about an hour, and heat the other part. I know this isn't what you asked for, but thought it may help.
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  3. #3
    Join Date
    Jun 2006
    Location
    Calgary, Alberta
    Posts
    377

    Default 4140

    I've welded a 4140 CrMo shaft to an unknown mild steel shaft that was guessed to be a mechanical grade, 70 ksi or so, it was a section about 8" in diameter and solid. The part was a broken pivot shaft that holds the track frame onto the main frame of a large mining drill.

    The procedure I used was provided to me as a guideline. After initial jig setup, I pre heated both sections of material to within 375F - 425F, tack welded the components, then completed the weld with a 80xx type lo-hyd electrode, not letting the inter-pass temps go over 500F. Interpass heating was used to keep the temp up. After completion, the weldment was wrapped with fire blankets to allow slow controlled cooling.
    I used a 2% nickel alloy 80xx low-hyd rod for the root and subsequent passes until the build up was sufficient to us LA-T91-C60 NI1 .045 flux cored wire to fill out the rest. This was completed in the horizontally fixed position so all welding was done from 6 oclock to 12. The weld repair was sucsessful and has had to work at temps below -40C, suffering mostly impact and torsion type stresses.
    I've also sucsessfully welded 4140 to mild in much smaller on-the-bench arrangments, and generally followed the same type of procedure. 350-450F preheat, controlled interpass temps, and let cool slowly.

    The use of a needle scaler to remove slag and inter-pass pein the weldment to remove stress was also employed in some of the repairs and so far there have been no come-backs.
    Jonny

    Dynasty 300DX
    Esab PCM 1000

  4. #4
    Join Date
    Sep 2005
    Location
    northern NJ
    Posts
    1,858

    Default

    I have always used wire from Rockmount Research when welding 4140 to mild steel. You can find them at www.weldit.com. All good advice you have been given so far. If this was brought to me to weld I would look into tig welding it first & then go from there.
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