how to avoid rust while heat treating carbon steel 1075

[ht3jyx]

we heat the parts, size of 5 cent coin, material 1075, to 1600 F and then quench at polymer water. then temper at 400 F. we always get some of parts, less than 5%, with rust stain. does anyone know how to avoid this.

by the way, we can not get required hardness if quenched in oil.

thanks,

yush

 

[kenvlach]

A corrosion inhibitor must be used in polymer systems -- protects both the system & parts.
De-ionized water should be used for initial & make-up water to minimize salt buildup.
Polymers degrade from both thermal exposure & bacteria. Bacteria can also degrade/eat corrosion inhibitor. Degradation products are often acidic.

Remedies: Use DI water, biocide, corrosion inhibitor, check pH & conductivity (~measures salt), filter (catches some yeast-type fungi). Seek help from the polymer vendor.

 

[arunmrao]

For a 1075 grade steel,why do you need that fast rate of cooling. try oil quenching,no harm and you avoid the possibility of rusting.

 

[ht3jyx]

arunmrao,

the wash process after oil quench left stain (not rust), probably from the soap used in wash tank, on the parts. and customer does not like it. the polymer gives gook looking to parts, but unfortunately some parts get rust. tomorrow i will do a ph test to the polymer according to kenvalach.

thanks,

 

[dbooker630]

As kenvlach has stated, contact the quenchant source. Most sources offer different types of polymer formulations with special additives (e.g. nitrite or nitrite-free, detergent) depending on your specific situation and whether the part is subjected to a finishing operation. The remedies listed should be performed by your vendor free of charge on a monthly basis to track the condition of your fluid. I would also check the temperature control system to see if the tank is consistent, if there are areas of stratification, and your vendor can determine if there is selective drag-out.

Of course, depending on your hardness requirements, why not consider a microalloy with forced air cooling from austenitizing temp!

 

[arunmrao]

A vibro polishing of the parts might help in removing any residual rust stains after a wash . The customer will like the final finish,which can be altered by changing the polishing media.

 

[ht3jyx]

kenvlach,

we use city water without di-ionize. the polymer ph is 8, and the quench solution is 9. is that a problem. what is the right ph i should maintain?

yush

 

[kenvlach]

ht3jyx,
That seems fairly normal, but really it depends on the polymer mfr.'s instructions for solution make-up & maintainance. You should already have this info and a vendor contact (maybe pennypinching management stuck you with some generic solution?). Some mfr. websites, alphabetically:
D. A. Stuart Company
4580 Weaver Parkway, Warrenville, IL 60555 USA

http://www.dastuart.com

Dow Chemical Company
2301 Brazosport Blvd., Freeport, TX 77541 USA

http://www.dow.com/polyglycols/ucon

Heatbath®/Park Metallurgical
8074 Military Avenue, Detroit, MI 48204

http://www.heatbath.com/park/products

Henkel [presumably they have quenchants]

http://www.henkelsurftechna.com/index.cfm?location=9

Houghton International Inc.
Madison and Van Buren Avenues, P.O. Box 930, Valley Forge, PA 19482-0930 USA

http://www.houghtonintl.com