An Overview of Heat Treatment in the Refining, Power, and Petrochemical Industry - Part 1

Introduction

Heat treatment has been used by mankind for centuries. While not as advanced as the controlled heat treatment we think of today in the refining, power, and petrochemical industries, the principles and philosophies of heat-treating metal dates back over 2000 years. It’s an age-old practice that has been fine-tuned through years of science and technology to become one of the most essential processes during manufacturing, repair, and fabrication requirements.

There are numerous reasons to heat treat along with a few different methods of heat treating. The use spans across many industries, including oil and gas, power, chemical, automotive, aerospace, and consumer product manufacturing (glass, knives, utensils, etc.).

In this article, we’re going to skip over the scientific foundations of heat treating. Instead, we’ll cover the techniques commonly used in the refining, power and petrochemical industry at a high level. We’ll focus on the basics, including the varying reasons to heat treat, the types of heat treating available, and methods of heat treating to achieve specific material properties. In addition, we’ll focus on the role mechanical integrity plays in heat treating, including special considerations and the role of inspection during the process.

What is Heat Treating?

In short, heat treating is a process in which a product is heated and cooled with precise controls to improve its properties, performance, and durability while maintaining the product's shape. Depending on the desired outcome, the variables of temperature and time can be manipulated to alter the material’s hardness, strength, toughness, ductility, and elasticity.

I used the term “product” because heat treating does not only apply to metals. Heat treating is also used to alter the properties of non-metallics, coatings, and even process fluids.

Temperatures may range as high as 2,400°F and the hold time at temperature may vary from only a few minutes to a few days or more, depending on the desired outcome and circumstances.

Equally, if not more important, than the temperature and hold time is the cooling time or cooling rate. Again, depending on the desired outcome, some products are cooled very slowly, some are cooled in ambient air, and some are quenched rapidly.