Quenching Bending: 6 Questions You Must Know for A Comprehensive Analysis

Quenching, as an important metal heat treatment process, is widely used to improve the hardness, wear resistance, and fatigue strength of metal materials. However, bending deformation during quenching is a common and challenging issue. It not only affects the dimensional accuracy and shape stability of workpieces but can also lead to their scrapping in severe cases. Therefore, understanding the causes, manifestations, prevention, and solutions for quenching bending is crucial for heat treatment engineers and metal processing professionals. This article will delve into six essential questions about quenching bending to help readers better grasp knowledge in this field.

1. What is Quenching Bending?

Quenching bending refers to the bending deformation that occurs in workpieces during the quenching process due to uneven cooling or uneven release of internal stresses. During quenching, metals are rapidly cooled from high temperatures, and the difference in cooling rates between the surface and core leads to the generation of thermal stress and microstructural stress. When these stresses exceed the yield strength of the metal, plastic deformation occurs, known as quenching bending. The manifestations of quenching bending are diverse, including overall bending, localized warping, or twisting.

What are the causes of quenching bending? The causes of quenching bending are complex and varied, mainly including the following aspects: 1. Uneven cooling: This is the primary cause of quenching bending. Due to differences in the shape, size, and thermal conductivity of the workpiece, the cooling rate at the surface and core of the workpiece varies. The side that cools quickly experiences faster contraction, generating tensile stress, while the side that cools slowly generates compressive stress. When these stresses exceed the yield strength of the metal, bending deformation occurs.

2. Uneven stress release: During quenching, thermal stress and microstructural stress develop within the metal. These stresses need to be released after quenching; if they are released unevenly, it can also lead to bending. For example, during tempering after quenching, improper tempering temperature or time can result in uneven stress release, causing bending deformation.

3.Workpiece shape and size: The shape and size of the workpiece have a significant impact on quenching bending. For instance, long strip-shaped workpieces are prone to bending due to the large difference in cooling rates at both ends; thin-walled workpieces, with lower stiffness, are also likely to deform during quenching.

4.Material properties: Different materials have different thermal expansion coefficients, thermal conductivities, and yield strengths, so the stresses and deformations generated during quenching vary. For example, high-carbon steel, due to its higher hardness after quenching and greater internal stress, is more susceptible to bending deformation.

5. Heating and cooling methods: Heating and cooling methods are also important factors affecting quenching bending. For example, heating too fast or too high temperature may lead to uneven internal temperature distribution of the workpiece; and improper cooling method (such as water quenching, oil quenching, etc.) may also lead to uneven cooling, resulting in bending deformation.

Sure, here is the translation: Three, How to Determine if Quenching Bending Has Occurred? To determine if quenching bending has occurred, you can use the following methods: 1. Visual Inspection: For simple-shaped, small-sized workpieces, visual inspection can be used to check for any bending deformation. Place the workpiece on a horizontal surface and observe whether it is parallel or perpendicular to the surface.