As a core equipment in industrial production and heavy lifting operations, the stability and reliability of the screw jack directly determine the safety boundary and operational efficiency of the lifting operation. To enhance the load-bearing capacity and corrosion resistance of equipment, mainstream production enterprises use ductile iron material to build the body structure. This material has become the preferred material for jack bodies due to its excellent mechanical properties and resistance to medium erosion. However, in practical applications, the problem of machine body cracking still occasionally occurs, and precise traceability is required from the following key dimensions:

1、 Core incentives at the manufacturing process level

Welding process defects and non-standard heat treatment processes are the main manufacturing reasons for body cracking. In some production processes, if the welding parameters are not set reasonably and the operating methods are not standardized, it is easy to cause quality problems such as poor weld formation and insufficient fusion; Meanwhile, if the subsequent heat treatment is not strictly implemented according to the process standards, it will lead to a significant decrease in the strength and toughness of the welding area, forming a weak mechanical performance zone. When the equipment is subjected to external forces, concentrated stress is prone to accumulate in that area, ultimately leading to welding cold cracks, which will continue to propagate and spread with the continuous application of stress.

2、 Dynamic factors in practical application process

Long term continuous loading of equipment is an important factor in inducing cracking of the body. In the lifting operation, if the concentrated stress exceeds the ultimate bearing capacity of the defective area of the body, initial cracks will form first; Subsequently, with the alternating stress caused by the homework cycle, the initial crack will extend towards both ends along the direction of stress conduction, and the length and width of the crack will gradually expand, which may ultimately lead to structural failure of the machine body.

From the perspective of cracking path, the cracking phenomenon of the ductile iron body of the screw jack often begins at the joint weld position. This area becomes a weak point of structural strength due to welding residual stress and material performance changes. After the crack is formed, it usually continues to develop along the weld direction towards both ends, and it is necessary to focus on quality control and daily inspection of this part.