In terms of structure and performance, the upset type sleeve is made of high-strength alloy structural steel (such as 45# steel). After quenching and tempering, its hardness and toughness are well-matched. The length of the sleeve is slightly longer than the standard type (usually 2-2.5 times the diameter of the steel bar) to fit the upset end of the steel bar. Since the effective cross-section of the steel bar end increases after upsetting, the stress area of the threaded section increases accordingly, making the tensile strength of the joint not only not lower than that of the steel bar base material, but even exceeding the base material strength by 10%-20%. It is especially suitable for structures bearing dynamic loads and heavy loads, such as the core tube of high-rise buildings, the main beam of long-span bridges, and the column network of heavy-duty workshops.

The construction process is divided into three steps: first, cold upsetting the end of the steel bar, using hydraulic equipment to extrude the end into a cylindrical thickened section, ensuring that the upset part has no cracks and uniform deformation; second, rolling straight threads on the upset section, with thread precision reaching grade 6H, and the thread length must cover the entire length of the upset section; third, tightening the processed steel bar and the sleeve, using a torque wrench to reach the specified pre-tightening torque (e.g., 320N·m for 25mm diameter steel bars) to complete the connection. The advantages of this process are: first, super-strong bearing capacity — the upsetting treatment makes up for the weakening of the steel bar section caused by thread processing, avoiding the joint from becoming a stress weak point; second, excellent seismic performance — it is not easy to loosen under repeated loads, suitable for projects in earthquake-prone areas; third, controllable quality — the upsetting process can be intuitively controlled through length and diameter detection, and the thread processing precision is easy to verify.

The upset type straight thread sleeve strictly complies with the Class Ⅰ joint standard in Technical Specification for Mechanical Connection of Steel Bars (JGJ 107-2016), and is widely used in key projects with extremely high requirements on connection strength and reliability. It is the preferred solution for steel bar connection in high-pressure and heavy-load environments.