Common Defects in Forging Processing (Cracks, Folds): Causes and Preventive Measures to Improve Product Quality

Common Defects in Forging Processing (Cracks, Folds): Causes and Preventive Measures to Improve Product Quality

In forging processing, cracks and folds are core defects that affect the quality of forgings. They not only reduce the mechanical properties of products but also may lead to fracture risks in subsequent processing. Identifying the causes of these two types of defects and implementing preventive measures is crucial to ensuring forging quality.

Crack defects are mostly caused by improper control of materials, temperature, and processes. In terms of materials, if the raw materials have inherent defects such as subcutaneous pores and inclusions, stress concentration is likely to occur at the defect sites during forging, which further leads to cracks. For temperature control, excessively high heating temperatures (exceeding the initial forging temperature of the material) will cause grain coarsening and reduce material toughness; excessively fast cooling speeds will generate thermal stress inside the forging, triggering cracking. In process operations, uneven forging force and excessive deformation will cause local stress of the forging to exceed the material's bearing limit, resulting in cracks. Prevention should start from three aspects: selecting high-quality raw materials without defects and eliminating hidden dangers through flaw detection before forging; strictly controlling heating and cooling speeds—for example, the heating temperature of carbon steel should be controlled between 1100-1250°C, and slow cooling methods (such as embedding in sand) should be used during cooling; optimizing the forging process to ensure uniform deformation and avoid excessive local stress.

Fold defects are mainly caused by improper forging operations or unreasonable die design. During forging, if the blank is misaligned or the same area is repeatedly hammered, the metal flow lines are prone to bending and overlapping, forming folds. Excessively small fillet radii of the die cavity and insufficient draft angles will hinder metal flow, resulting in fold marks on the surface or inside the forging. Preventive measures include: accurately positioning the blank before forging to ensure uniform force application and avoiding repeated hammering on the same part; optimizing die design by increasing the fillet radius of the cavity to 5-10mm and controlling the draft angle between 3°-5° to ensure smooth metal flow; regularly inspecting the forging appearance during the forging process and adjusting the process in a timely manner if early fold signs are found to prevent defect expansion.

Through these measures, crack and fold defects can be effectively reduced, and the quality of forging products can be significantly improved.