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  • Users: HardMetal
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  1. HardMetal

    Reason for Stress Corrosion Cracking

    Thanks for your help, Metengr. I've done internet searches and I can't find anything specifically describing how stersses affect the role played by thermodynamics or kinetics. Do you know of any sources?
  2. HardMetal

    Reason for Stress Corrosion Cracking

    Why does the application of stress to a part produce a different corrosion mechanism other than just the type of corrosion that would occur without the application of that stress? Does thermodynamics or kinetics play a role in the process? Is it a matter of changing the fracture toughness...
  3. HardMetal

    salary negotiation advice needed ASAP!!!

    I don't think that there should be a problem telling a prospective employer what you are making or made previously. No matter what offer they come back with, you can still reject the offer and requrest an increase if you think you're worth it. I went for an interview several weeks ago after...
  4. HardMetal

    How much "un-paid" overtime is reasonable?

    Hourly wage = salary / 2080. 2080 = number of hours worked during a year (40 x 52).
  5. HardMetal

    Melting Moly

    I believe that moly oxides sublime. There was no significant loss of dimensional propreties from the outside of the samples, so I am not convinced it's oxygen contamination. We're still looking into this, but haven't come up with an answer yet. Thanks everyone for your suggestions.
  6. HardMetal

    Melting Moly

    During a CTE test, a stack of pure molybdenum samples (each 0.067 inch thick) was heated to 4000F. Melting of the material was noted in the center of the samples. Moly shouldn't melt until around 4700F. So I figured that there must be an alloy or some contamination of the base metal. We did...
  7. HardMetal

    Aluminum corrosion

    Thanks for all your suggestions
  8. HardMetal

    Welding 7075 aluminum

    Thanks for the info.
  9. HardMetal

    Welding 7075 aluminum

    Can 7075-T6 aluminum alloy be welded? If so, by what process? Thanks.
  10. HardMetal

    Keep razor blades sharp

    Blades are made from various materials: see http://www.specialtyblades.com/ I use individual razor blades for several weeks with no special care. So why the concern with corrosion? I've never seen corrosion on razor blades. Maybe your water has low pH. IRFs: It is not only oxygen that you...
  11. HardMetal

    Aluminum corrosion

    Metalguy: We were thinking of doing the salt spray test but we're not sure if the program has the money. The salt spray test would be good to try. I've recommended that as something that should be done, if affordable. We don't want the rivets to be too high in strength otherwise it will be...
  12. HardMetal

    Aluminum corrosion

    I am looking to replace aluminum rivets used in a 6063-T6 aluminum structure. The main reason is to reduce assembly costs. I am thinking of using Monel 400 or 304 stainless steel. Their higher tensile strength will reduce by 1/2 the number of rivets. I am concerned about galvanic corrosion...
  13. HardMetal

    Paraffin corrosion of 17-7PH

    Does anyone have any information on the corrosion of 17-7PH by a hydrocarbon fluid called isoparaffins, specifically ISOPAR H made by Exxon? Is there any reason to assume the hydrocarbon fluid would be corrosive? I've been unable to find any information on this. The properties of the material...
  14. HardMetal

    Rewelding of 17 - 4 PH

    We have GTA welded the structure in the H925 and then re-heat treated at 925F for 4 hours. Mechanical tests have proven acceptable: the structure was pressurized and did not fail at a pressure well above the required operating pressure (MEOP). There was no problem with distortion.
  15. HardMetal

    Overaging of 17-4PH

    Thanks for your help. I spoke with someone from AK Steel and he said essentially the same thing, that the properties would not be significantly affected.
  16. HardMetal

    Overaging of 17-4PH

    Do the mechanical properties of 17-4PH in the H925 condition degrade significantly if it is aged an additional 4 hours at 925F? If so, do you have any data showing how much? Thanks. Paul
  17. HardMetal

    Rewelding of 17 - 4 PH

    Thanks. That was my opinion also but I was hoping someone had another idea or way around it. It's not a structure that can be reheat treated. It's a complex shape of sheet metal welded together. Re-heat treating would cause extensive distortion. Paul
  18. HardMetal

    Rewelding of 17 - 4 PH

    I realize that, of course. We do need full strength as the corner is a highly stressed area.
  19. HardMetal

    Rewelding of 17 - 4 PH

    I have a complex structure that was assembled by electron beam welding 17-4PH sheet (0.090 inch thick) in the corners. The sheet is now in the H925 condition. The welds were supposed to be full penetration welds, but turned out to lack full penetration. They are around 0.050 - 0.070 inch...
  20. HardMetal

    YS and UTS for an all weld tensile specimen

    sayeeprasadr, I'm not sure how you expect to measure yield strength by that method, but that is not the correct method. How would you know when you've reached 0.2% permananent deformation? It's not possible to do that visually. How do you know when the curve started to deviate from linearity...

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