Where the
world gathers for metal finishing
Q&As since 1989


-----

Superficial cracks on Induction Hardened Steel

December 1, 2009

We have an problem that seems to repeat itself
we out source Induction Hardening of Piston Rods of Various size 125 mm-160 mm and length of almost 3 meters material used is En-9. Carbon @4.5%,
our vendor say he stress relives these shafts after induction Hardening
we have the following problems:-
1. these shafts tend to bend in the center 1 mm - 2 mm
2. some times there are cracks visible in grinding process
can any one enlighten us the correct process for induction Heat treatment

MAHENDRA GARGATTI
PLATING SHOP OWNER - BELGAUM, KARNATAKA, INDIA

---

I am not familiar with your steel, but any bending will normally be from not being properly supported during the oven run or the rods not going into the quench vertically. If you go in horizontally, the rods tend to warp if not perfectly horizontal and even if it is,it may not be rapid enough going into the quench.

It was my experience on much smaller parts that hardening based cracks tended to be large. Abusive grinding MAY be causing your cracking.

James Watts
- Navarre, Florida
December 2, 2009

Are you sure about that carbon content? A level of 4.5% corresponds to cast iron not steel. Could it be 0.45% instead?

Guillermo Marrufo
Monterrey, NL, Mexico
December 14, 2009