As every heat treater – captive or commercial – knows, distortion will occur. The heat treater must recognize the many reasons why distortion occurs. This applies to both ferrous and nonferrous materials.

Distortion happens and will continue to happen. The manufacturing process sometimes makes it worse, but nothing can completely eliminate it. We can, however, take steps to reduce it.

The writer was once told, “If distortion occurs, go back to the beginning.” At that time, I did not grasp the real and full meaning of that statement. It is normal to say, “Distortion occurred during the final heat treatment.” That is very true, but the distortion cause could have been established at the very beginning of material manufacture for either ferrous or nonferrous material.

In other words, the distortion exhibited at final heat treatment may well have its root cause at any of the following:

• Material – primary material analysis variations within specification
• Production – rolling operations
• Production – forging operations
• Production – engineering design contributions of sectional thickness changes
• Production – abusive machining operations
• Heat treat – heat-treatment operation with quench (phase change)

Figure 1 presents a summary of most of the contributing factors to the distortion phenomena. It also presents a suggested timeline of when changes will occur in relation to the manufacturing procedure. But if we know all of this, why can we not control and eliminate it?

We will not be able to address all of these factors, so next time we will begin the discussion of material and heat treatment.