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  1. MFAMET

    Axle failure, thoughts

    the fractured surface exhibits many concentric circles coupled with a "fiber" small circle at the center. In addition, there is no obvious fracture origin. This all suggests it is a rotational fatigue fracture under high stress conditions along the end edge of shaft. The smaller radius could...
  2. MFAMET

    Hydrogen Embrittelment

    phosphoric acid solution could cause hydrogen embrittlement depending on the concentration, temperature and duration A non-residual stress release part could cause cracking while submerged in the acid solution. This is called stress corrosion cracking (SCC). A simple test could determine...
  3. MFAMET

    HT300 casting material - normalisation and tempering

    ASM Handbook, "Heat Treatment" covers the approaches how to perform the heat treatment for all cast irons, such as grey, white, malleable and other cast irons. The normalization is performed to restore the altered properties of grey cast iron to the as-cast iron. The normalized temperature is...
  4. MFAMET

    Knife-line Attack prevention when welding 321 SS

    I should make it more clear for my previous common. KLF is a very thin film perhaps, a few mms wide. It lies at the very vicinity of the molten weld. For some cooling regimes, TiC (or NbC) precipitates are dissolved, but instead, CrC precipitates are formed. The steel becomes unstsbilized in...
  5. MFAMET

    Knife-line Attack prevention when welding 321 SS

    The starting dissolution temperatures of TiC and CrC are 1900F and 1450F, respectively. Therefore, if the welding temperature could be maintained at 1550F-1750F, this will prevent both of the TiC dissolution and the formation of CrC. This result will greatly decrease the deletion of Cr along the...
  6. MFAMET

    Knife-line Attack prevention when welding 321 SS

    As a stabilized steel, such as 321SS, a low heat input could avoid the dissolution of TiC (1900F or above) which is designed to tie up free carbons. However, if the input heat is too low, the weld quality could be compromised, such as the reduction of toughness with others
  7. MFAMET

    How much hardness change can I expect from a low-level stress relief on a 17-4 SS part?

    17-4 PH SS is a tempered martensite. Normally, the tempered martensite hardness will drop with tempering temperature over 650F. !7-4 PH SS hardness increasing is due to the formation of carbide precipitates However, there is "tempered martensite embrittlement" occurring at 480-570F...
  8. MFAMET

    Knife-line Attack prevention when welding 321 SS

    Inconel alloy 112 or others is an optional metal for 321 SS welding filler due to its less galvanic corrosion and is metallurgical compatible with SS. KLA is caused by high heat which dissolves both Ti and Cr carbides. If you re-heat the welded material at 1850-1950F, this will allow Ti to...
  9. MFAMET

    Fatigue damage and heat treatment

    as I mentioned previously, the fatigue crack starts from material surface due to the formation of "slip bands" by a greater tensile stress on surface. The failure caused by the interior defect, such as voids or microcracks is very rare. The used parts could have minute cracks on surface...
  10. MFAMET

    1215 Hot Rolled vs Cold Rolled

    1215 is not thermally hardenable due to the low carbon. The HR mechanical properties are basically determined by rolling temperature and cooling rate. So, why you have to concern any heat treatment? The only thing you need to ask is the HR tensile strength. Cold rolling could bring up some...
  11. MFAMET

    Fatigue damage and heat treatment

    Fatigue failure usually starts from the surface where it receives the max tensile stress during application. This implies a hardened surface and/or a defect free surface could improve the fatigue life. A tensile residual stress could reduce the fatigue life. The fatigue life is limited under a...
  12. MFAMET

    Need to improve Charpy Results

    By reducing both temps to 1700F and 1650F, respectively, you could get the finer grains which could boost toughness. Also, by increasing the tempering temperature, you will increase the ductility and toughness but it might cost some of the material strength.
  13. MFAMET

    Optimal Splined Shaft Material for Low Cycle Fatigue

    This attached diagram was taken from AMS Handbook, "Heat Treatment"https://files.engineering.com/getfile.aspx?folder=a2312823-b22f-43a3-b716-4f8e69bc2842&file=oxodocumentconverter.pdf
  14. MFAMET

    N&T 4130 impact properties?

    In order to enhance the impact energy, other than the concerns on TS and ductility, you could try to refine the grain size by minimizing the normalization time and maintain temperature not to exceed 1650F. you also could ask for a small amount of Ti or V in the liquid steel to get a fine structure.
  15. MFAMET

    Need help welding heat treated steels

    I though we were talking about the pre-heat prior to welding for already carburized parts instead of the tempering during the manufacturing processes. The preheat itself should take much shorter time than tempering. So, the hardness dropping may not be necessary profound.
  16. MFAMET

    Need help welding heat treated steels

    In order to avoid the cracking during welding and to alleviate the effect of(residual) thermal stressing after quenching, 800F pre-heat is an appropriate process. But it could also reduce the hardness of carburized workpiece in the heat affected zone by the formation of more tempered martensite...
  17. MFAMET

    Need help welding heat treated steels

    your preheating and water quenching practices appear good. Just make sure the welding temperature does not exceeds 1000F during quenching. These two dissimilar(1018 and 8620) metals may not cause severe galvanic corrosion issue due to the light difference of electrode potentials.
  18. MFAMET

    Alternat; ASTM A487 Gr10B

    The Hadfield austenitic manganese steel for a128 grade is highlighted by its wear resistance and high impact energy. In order to maximize those properties, solution annealing coupled with Ti addition may need to be considered. iorder
  19. MFAMET

    Stud bolts to ASTM A320 Gr L7M - Decarburization test

    yes, I agree to your thinking. You have to follow A962 spec per A320 spec. a The decar could be partial or full in depth and it should be defined in A962.
  20. MFAMET

    Heat Treatment cycle to achieve hardness of 400-500 BHN in alloy steel casting.

    Water quenching is an approach of severe quenching. Your as-quenched hardness, HB 300 is well below than expected. There are two possibilities contributed to that. First, the quench rate is too slow. you need to ensure the quenching is performed as quick as possible (in a few seconds). Second...

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