Mass effect
Due to the size, that is, the mass of the treated parts, the heat treatment results, especially the quenching results, are different, which is called mass effect.
Usually, the thicker the diameter of the steel part, the harder it is to harden through; the thinner the diameter, the easier it is to harden through. The difference lies in the mass effect. The so-called large mass effect means that the heat treatment results caused by different masses are different. It means that the larger the parts, the more difficult it is to quench. For small mass effects, not to mention small parts, even large parts can be hardened through.
Carbon castings are an example of steel with large mass effect, and chromium-molybdenum steel and nickel-chromium-molybdenum steel are examples of steel with small mass effect. Due to the different sizes of parts, the different quenching effects are mass effects; and due to different steel types, the different quenching effects are hardenability. This is to analyze the quenching effect from different angles, and hardenability is to analyze the quenching effect from the material angle of steel.
Therefore, steel with good hardenability has a small mass effect, and even large parts can be hardened. In other words, it is the hardenability that can improve the mass effect. The alloy elements that effectively improve the hardenability include boron, manganese, molybdenum, chromium, etc.
Shape effect
The quenching effect is affected by the shape of the part. Different shapes such as bars, plates, and balls have different quenching effects. In addition, even for the same treated parts, the quenching effect is different due to different quenching locations and different cooling methods. This effect caused by the shape of the part is the so-called shape effect.
The ratio of cooling effect is ball: round bar: plate = 4:3:2. The difference in cooling effect due to different locations is that if the flat plate is 1, the dihedral angle is 3, the trihedral angle is 7, and the concave angle is 1/3.
Size effect
The mechanical properties of steel are not determined by the material alone. They change with changes in shape and size. Usually, the larger the size of the steel, the lower the mechanical strength.
This change in mechanical properties with changes in shape and size is called size effect. The most prominent mechanical properties that show size effect are fatigue strength, tensile strength and wear resistance, which also have size effect, so they should also be paid attention to.
