4150 needs 55 Rc at surface.

[ibf]

Hello:

16 pieces , 3" thick x 2" dia ( solid - big dounut); quenched in oil (1500F FOR 3 HOURS) ; TEMPERED AT 660 F for 2 1/2 hrs. Quenched vertically to minimize steaming that encapsulates the surface upon cooling ( 2" spacing between each piece). Furnace has controlled atmosphere , oil tank has agitation and cooling system , one test piece was made prior to production and the result was satisfactory. After quenching 16 at above conditions the hardness at surface was 43 Rc.Heat treatr claims that such an alloy cannot achieve 55Rc by quenching 16 at a time. Suggested increase austenitizing temperature to 1600 F. hE CLAIMSthe risk of cracking is high. What do you suggest should be done ?

ibf (mining)

 

[metengr]

It appears that the heat treater had overtaxed the oil bath system for quenching 16 pieces at one time. If one piece turned out ok, the oil tank may not be able to dissipate the heat from the added pieces to achieve the necessary cooling rate for surface hardening. Increasing the austenitizing temperature will only make matters worse in terms of increasing the risk of quench cracking and not being able to remove the added heat (higher austenitizing temperature) for quenching.

If the heat treater is limited as to the amount of cooling/agitation for the oil tank, I would not change the original austenitizing temperature. Instead, I would reduce the number of pieces to be quenched per batch from 16 to possibly 8 or fewer to achieve the required conditions for oil quenching.

 

[arunmrao]

Does the heat treater have polymer quenching faclity. A faster rate of quenching than oil but without the fear of cracking can give you RC 55 comfortably. I regularly use this for my castings without much problems.

 

[ibf]

I have to check that out ( not sure they have it ). I know for sure they have water tank.

ibf(mining).