Is Heat Treatment for Metal a Special Process?

[Big Jim]

They really do need to do more in my mind. At the very least they should be able to explain or defend how they are validating it. A hardness test may or may not be enough depending on circumstances, but they are completely missing 7.5.2 d concerning the need to maintain records for validation.

They need to sit down and read all of 7.5.2 and become prepared to show what validation is needed for their circumstances and they also need to determine what records are needed and start keeping them.

 

[Lexylou]

Big Jim,

I thank-you for your response because I know that there is more they need to do in order to meet the requirements. I'm trying to guide them is this ISO certification process and I have had no experience in Special Processes.

I am planning a meeting with all of those involved so we can discuss this. This thread including your response will be apart of that discussion. Is there anyone that has an example that I can use as a guide to where I can start? I would probably need the same for welding too.....

 

[w_grunfeld]

The criticality factor was related to weldments and specifically for the level of inspection required as a function to criticality.
Heat Treatment is a different process, and basically in order to be effective all that is required is that temperature and time be controlled. Even if the part is not critical, the purpose to heat treat is to achive a hardness level as specified on the blue print. You have to record for each batch that the required time and temperatures where maintained. If the part was subjected to 2 hrs in the oven instead of say 4 hrs, or 150 deg instead of 200, the part, critical or not ,is not going to have the intended hardness.
So what you need is to be able to show that each parts batch was exposed to the correct temperature and time. It also follows that you have to periodically calibrate (verify) that the indicated temperature is indeed correct

 

[ABCquality]

Hi all,

A special process is any production or service delivery process that generates outputs that cannot be measured, monitored, or verified until it's too late. It's often too late because deficiencies may not be obvious until after the resulting products have been used or services have been delivered. In order to prevent output deficiencies, these special processes must be validated in order to prove that they can generate planned results.

I believe the above definition applies for Heat Treatment. In my company, postweld heat treatment is a special process which requires personnel and procedures to be approved before work.

Regards,
Richardo

 

[David Hartman]

Just let me share one more though with you, were there many competitors competing for a chunk of business??? Were there laid down specifications those days? IMO - no!!!!!

Actually there were competitors hence the reason that certain craftsman's works are more valuable than others, and yes there were "laid down specifications" in that the craftsman taught their apprentice precisely how to duplicate his work (OJT).

BTW: I worked for a company that required heat treating of some small steel covers not for increased hardness, but for the change in the metals magnetic properties. So verifying the hardness would not have validated the process at all.

 

[p_mani888 - 2010]

Heat treatment is indeed a special process, whether your sole activity is only heat treatment or not.
If you are supplying / sub-contracting this heat treatment activity to any of the BIG 3's / IATF customers / their TIER vendors, you need to have your process qualified for CQI 9 requirements.

 

[w_grunfeld]

The same applies to many other industries not just automotive, defense for example.....

 

[achorste]

BTW: I worked for a company that required heat treating of some small steel covers not for increased hardness, but for the change in the metals magnetic properties. So verifying the hardness would not have validated the process at all.

Validation can only be performed against the specification requirements - if this was hardness, grainsize or magnetic properties - these would be the factors that are validated against.

A special process is any production or service delivery process that generates outputs that cannot be measured, monitored, or verified until it's too late.

I would disagree with this definition - A special process is one where the output cannot effectively inspected, tested or verified.

An example - I worked on a blasting process that had to achieve a specific surface finish (between 6 and 20 Ra). Obviously we can measure surface finish, but only at discrete points, measuring the surface finish at every point would be completely excessive, take far too much time and just be ridiculous. Hence it was treated as a special process and was validated.

This has a parallel in heat treatment - hardness can only be measured at discrete points on the surface on the product, grainsize at sections where it is cut up mounted & polished etc etc

How do you know the heat treatment process gives even properties across the component? Different component geometries, variations in the component before heat treatment, variations in temperature uniformity across the furnace or heating process and many other factors can affect these properties - hence without validation of the process at the worst case limits of the variables, or combinations of variables, hardness testing each output from the process is insufficient.

Heat Treatment is a different process, and basically in order to be effective all that is required is that temperature and time be controlled.

What about cooling rates, atmosphere, pressure etc etc? Are there not plenty of other variables that would need to be considered?

So what you need is to be able to show that each parts batch was exposed to the correct temperature and time. It also follows that you have to periodically calibrate (verify) that the indicated temperature is indeed correct

Process records like these do not validate the process. To validate the process you would need to show the process, even at the worst case limits of each variable or combination of variables still produces conforming product. The process records would then be of use in showing that the manufacturing process conforms to this validated process.