Heat Treatment: Do You Really Know the 3 Effects?


The effects of heat treatment can vary based on the materials and treatment methods used on the parts being treated. Even if the same material undergoes the same heat treatment method, the effects can differ due to the varying sizes and shapes of the parts being treated. These influencing factors are collectively referred to as “effects,” and there are three types of effects.

Effects of Heat Treatment

1. Quality effect

Due to the different sizes and qualities of the processed parts, the heat treatment results, particularly the quenching results, can vary. This is known as the quality effect.

In general, the larger the diameter of the steel, the more difficult it is to harden, whereas the finer the diameter, the easier it is to harden. This difference is attributed to the quality effect, which refers to the significant difference in heat treatment results caused by different qualities of the steel. Therefore, the larger the part, the harder it is to quench, whereas small parts with small mass effect can be quenched even large parts.

An example of steel with a large quality effect is carbon casting, while chromium molybdenum steel and nickel chromium molybdenum steel are examples of steel with a small quality effect. The quenching effect differs due to the size of the parts, but it also differs depending on the type of steel and its hardenability, which is analyzed from different angles and from the perspective of steel material.

2. Shape effect

The quenching effect is influenced by the shape of the parts.

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Different shapes, such as bars, plates, and balls, can have varying quenching effects.

Furthermore, even when processing identical parts, their quenching positions and cooling methods may differ, resulting in differing quenching effects.

This influence resulting from the shape of the parts is commonly known as the shape effect.

The ratio of cooling effect is as follows: Ball: Round rod: Plate = 4:3:2.

The cooling effect varies across different parts. For instance, if the cooling effect of the flat plate is taken as 1, the cooling effects of the 2-face angle, 3-face angle, and concave face angle are 3, 7, and 1/3 respectively.

3. Size effect

The mechanical properties of steel are not solely determined by the material itself, but also vary depending on its shape and size.

In general, steel exhibits lower mechanical strength as its size increases.

The phenomenon where mechanical properties vary with changes in shape and size is known as the size effect. This effect is particularly notable in mechanical properties such as fatigue strength, tensile strength, and wear resistance. Therefore, it is crucial to pay attention to these properties and their size effect.


After reading this article, I believe you have a better understanding of the three effects of heat treatment.

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