Heat Treat Tips: Testing & Compliance

During the day-to-day operation of heat treat departments, many habits are formed and procedures followed that sometimes are done simply because that’s the way they’ve always been done. One of the great benefits of having a community of heat treaters is to challenge those habits and look at new ways of doing things. Heat Treat Today’s 101 Heat Treat Tips, tips and tricks that come from some of the industry’s foremost experts, were initially published in the FNA 2018 Special Print Edition, as a way to make the benefits of that community available to as many people as possible. This special edition is available in a digital format here.

Today we continue an intermittent series of posts drawn from the 101 tips. The tips for this post can be found in the FNA edition under Hardness Testing, CQI-9 Compliance, and Hardening/Tempering. 

Heat Treat Tip #22

Inspection Mistakes That Cost

Rockwell hardness testing requires adherence to strict procedures for accurate results.  Try this exercise to prove the importance of proper test procedures.

• A certified Rc 54.3 +/- 1 test block was tested three times and the average of the readings was Rc 54 utilizing a flat anvil.  Water was put on the anvil under the test block and the next three readings averaged Rc 52.1.
• Why is it so important that samples are clean, dry, and properly prepared?
• If your process test samples are actually one point above the high spec limit but you are reading two points lower, you will ship hard parts that your customer can reject.
• If your process test samples are one point above the low spec limit but you are reading two points lower, you may reprocess parts that are actually within specification.
• It is imperative that your personnel are trained in proper sample preparation and hardness testing procedures to maximize your quality results and minimize reprocessing.

Submitted by Young Metallurgical Consulting

Heat Treat Tip #25

CQI-9 Best Practices

Whether you need to meet rigid CQI-9 standards or not, what are the top 3, nay 4 best practices that nearly every in-house heat treat department ought to follow to make sure their pyrometer stuff is together?

Daily furnace atmosphere checks. Use an alternative method to verify your controls and sensors are operating properly and that there are no issue with your furnace or furnace gases.

Daily endothermic generator checks. Using an alternate method to verify your control parameter (dew point typically) or the gas composition is accurate will alleviate furnace control issues caused by bad endothermic gas.

Verify/validate your heat treat process every 2 hours OR make sure process deviations are automatically alarmed. this is a solid practice to ensure your controls and processes are running properly. This practice can help ensure that parts are being heat treated to the proper specification intended.

Conduct periodic system accuracy tests (SATs) per pre-defined timelines in CQI-9. Good pyrometry practices are an essential part of heat treatment. Because of the importance of temperature in heat treatment, ensure timeliness of all pyrometry practices addressing thermocouple usages, system accuracy tests, calibrations, and temperature uniformity surveys.

Submitted by Super Systems, Inc.

Heat Treat Tip #28

Control of Back Tempering With Induction Heat Treating

Induction heat treating is a selective hardening process. When hardening an induction path close to an area that had previously hardened, the heat from the hardening the second path tempers back the area that was previously hardened. This is a particularly common issue when tooth by tooth hardening of small gear teeth. Back tempering will reduce the hardness on the adjacent area and this effect may range from a few to over 10 HRC points.

Factors to Minimize Back Tempering 

Submitted by Midea Group, Inc.