S7 Warped in Heat Treat, HELP!

[premiertool]

What is the most likely cause of warping? Is the warping due to quenching from a high heat? Or could it be residual stress in the steel?

How would we go about reversing the warping effect, Can we re-heat treat without annealing first?

When the block was removed from high heat, the front of the block (which is now concave from warp) cooled faster then the back, could this have caused the warping?

Size, 2x10x13 (inches)

 

[swall]

You need to supply some details, such as the austenitizing temperature, time at heat and quench media.

 

[premiertool]

1375 pre-heat for 15 minutes, 1750 degrees, 1 hour at peak heat, quenched by fan and Pressurized air hoses.

We have a warped block, if we re-heat it, can we get rid of the warp?

 

[Maui]

Heat treatment parameters for S7 can be found here:

http://www.crucible.com/eselector/prodbyapp/plastics/crus7p.html

There are many possible explanations for the distortion that you observed. A more detailed description of your material processing and component production steps will lead to a more meaningful response. Uneven heating to temperature or of heat removal during quenching can easily cause warping and distortion of such parts. In severe cases it can lead to cracking. This is especially true if there are large changes in section thickness in certain areas. Residual stresses can also aggravate such issues. You will need to re-anneal this part before heat treating it a second time. To remove the warping, you will likely need to mechanically straighten the part. How you do this will matter a great deal. Be careful in the decision you make in this respect. I would suggest that you perform the straightening after re-annealing.

Note that if your block is 3" in thickness or more, you will need to use an oil quenching technique to develop a complete through-thickness hardening response. Can you provide a description of the part geometry or a photograph? What type of heat treating furnace was used (salt bath, fluidized bed, atmosphere controlled production furnace, etc)?

Maui

http://www.EngineeringMetallurgy.com

 

[premiertool]

the block is 13 in. X 11 in. X 2 in. it has numerous holes and water lines drilled. We wrap in SS foil and double fold the seams. The part was lain flat on 1/2" dia SS rods so there is good air circulation. We have been doing our heat treat this way for years and can usually get S7 to about 61 RC out of high heat then draw it back to about 55 RC always tempering twice at about 600 degrees. This block is larger than we usually do and we left extra grind stock in case it warped, but it warped more than we expected.

 

[CoryPad]

The distortion likely is due to quenching. Your part is very thin relative to the length and width so it will be susceptible to variation in quenching severity on each side (air flow rate, temperature, etc.). Can you immerse the part in a quenchant?