Cracks with Induction heat treating of 1144 steel
Cracks with Induction heat treating of 1144 steel
(OP)
I have started with a company that uses induction heat treating on a part made from 1144 steel. The part is an adapter with the OD .73", ID .5" and .46" length with external threads. The requirements of the customer are HRC 59 min with a case depth of 0.01" - .100". We are experiencing circular cracks and melted threads periodically. The operators can only adjust the amount of water used when quenching and the voltage. There are no set variables for these. I am looking for any kind of advice of temperatures and time at heat treatment and after quenching. These parts are not tempered. They claim that they have never had this problem in the past 11 years.





RE: Cracks with Induction heat treating of 1144 steel
Reality #1: Everybody does it.
The cracking and melted teeth sound to me like the operator has turned the power up to get the hardness (or slowed down the scan rate).
The operator may have done this because the parts are not getting hard. This may be due to plugged quench ring, wrong polymer concentration, or even poor lot of material. You may also see if the operator is double hardening them (running them twice).
59 HRC is pretty high for this material.
RE: Cracks with Induction heat treating of 1144 steel
RE: Cracks with Induction heat treating of 1144 steel
What is the quenchant?
What is the temperature of the quenchant?
What is overall length of the part?
What type and brand of induction machine?
How much space between the coil and the part?
Do the cracks run along the length of the part?
Can the cracks be seen while heating in the coil?
Please don't double harden without annealing between. The risk of cracking gets very bad.
RE: Cracks with Induction heat treating of 1144 steel
RE: Cracks with Induction heat treating of 1144 steel
Consider using a water-based polymer such as aqua quench 364. It may help the cracking. Also, you may want to monitor the temp of the part after quenching. There is no need to quench below around 400degF (that is, it can air cool from 400). Maintaining a minimum hardness of 59 HRC is unrealistic. 1144 has a minimum carbon content of 0.40% which will only develop a maximum hardness on quenching of 56 HRC. I would not want to use these parts without any temper; even a 400 deg F temper is better than nothing.
Nearly every problem I run into I get told that they never have had this problem before. Almost always, it's the same old problems, just a new day.
RE: Cracks with Induction heat treating of 1144 steel
I believe this is a crack due to the severe water quench.
As the parts set for a while, and the shop is quiet, you may even hear them crack. They may even crack while in use. Untempered water quenched 1144 overheated in an induction coil is not a good story to tell a customer.
Redpicker is right. I get that "never had the problem before" reply all the time.
RE: Cracks with Induction heat treating of 1144 steel
RE: Cracks with Induction heat treating of 1144 steel
RE: Cracks with Induction heat treating of 1144 steel
= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Cracks with Induction heat treating of 1144 steel
http://www.houghtonintl.com/
RE: Cracks with Induction heat treating of 1144 steel
Houghton International
RE: Cracks with Induction heat treating of 1144 steel
Water quenching is not recommended for 1144. Oil quenching would not result in a thermal shock and the possibility of cracks will reduce with oil quenching.
The safe hardness for 1144 with my experience is about 45-50 HRc.
Having said that it is also important to note that circular cracks are a result of unveen cooling due to water. There may be some contamination in the heta treat tooling or formation of bubbles in water etc.
Secondly threads are inherently prone to cracking. Is it possible for the heat treater to mask it to prevent hardening?
RE: Cracks with Induction heat treating of 1144 steel
The cracking could be caused by overheating, the word melting indicates you may be overheating. Overheating will cause cracking. Depending on how much sulfer is in the bar, and if it has any stringers of sulfur and how close the stringers are to each other can cause cracking in 1144.
Can you vary the scan speed?
Fred Specht
847-606-9462