Development of a new type of weld rolling machine

**Development of a New Type of Weld Rolling Machine** **Sun Lihua, Zhang Baoqing** **Abstract:** To address the issue of excessive residual stress in stainless steel welds commonly found in industries such as packaging, chemical, pharmaceutical, and food, this paper introduces a novel double-roller single-active transmission system. This method is used to develop a crushable flat plate and cylinder roller compactor capable of handling stainless steel with wall thicknesses ranging from 3 to 8 mm, as well as straight and ring welds. The rolling process corrects the appearance of the welded joint, adjusts internal structure and defects, and reduces residual stress by approximately 50%, significantly outperforming traditional grinding methods. **Keywords:** weld, stainless steel, roller, residual stress **Introduction:** Stainless steel welds are widely used across various industries. However, improper treatment can lead to unsightly appearances, high residual stress, and increased susceptibility to corrosion and contamination. These issues affect the quality of manufacturing equipment, product pricing, and market competitiveness. Traditional methods like polishing, grinding, and chemical cleaning have limitations—polishing is labor-intensive, while chemical cleaning only removes surface discoloration without addressing structural issues. In contrast, the weld rolling method offers a faster, more efficient alternative with no consumables and a smoother finish. It is particularly suitable for stainless steel and aluminum alloy products requiring a clean, smooth surface. **Challenges in Weld Processing:** Straight-line welds often cause warping or uneven height, while ring welds may form significant tensile stresses upon cooling. This leads to deformation, affecting the structural integrity of the workpiece. Methods like mechanical stretching and temperature differential stretching are time-consuming and inefficient. Therefore, weld rolling has become a necessary step in pressure vessel manufacturing. Compared to traditional techniques, the rolling deformation process offers advantages such as improved surface roughness, higher hardness, favorable compressive residual stress, and enhanced fatigue strength and corrosion resistance. It also refines the metal structure, making it more durable. **Market Limitations and Need for Innovation:** Currently, most weld processing machines on the market are cleaning devices, which are expensive. Although some roll mills exist, they are often specialized tools with limited specifications. The maximum weld bead length they can handle is usually less than 2600 mm, and the rolling thickness is typically under 6 mm. A new machine that is simple, efficient, and versatile for both straight and annular welds with varying sheet thicknesses would be highly beneficial. Many companies still rely on costly special rolling machines or grinding methods, but the results are often unsatisfactory. Thus, there is an urgent need for a practical and cost-effective stainless steel weld rolling mill. **Working Principle of the Roller Compactor:** The roller compactor applies different levels of rolling pressure to the weld area, causing plastic deformation of the metal. This process rearranges the lattice structure, increases density, and reduces residual stress. As a result, the weld zone becomes longer, and the original deformation caused by stress is restored. This improves surface hardness, eliminates welding stress, and flattens the surface. **Transmission System Design:** The roller compactor uses a single active transmission system, which is simpler, more compact, and easier to maintain. Unlike dual active systems, it allows stable rolling in both vertical and horizontal directions and supports different wheel diameter ratios. This makes it ideal for a wide range of applications, including small-diameter workpieces. **Implementation Details:** As shown in Figure 2, all working components are mounted on a frame and fixed using expansion bolts. The motor drives the gear system, which rotates the driving roller and causes the can body to rotate. Manual cranking provides adjustable rolling pressure, while a lifting platform enables precise positioning for different weld types. **Key Component Design:** The roller is made from Cr12MoV alloy steel, with a hardness exceeding 57HRC. The column and base are constructed from H-shaped steel, ensuring sufficient rigidity and stability. A 3kW motor with a high torque output ensures consistent performance and effective rolling force. **Performance Improvements After Rolling:** The appearance of the weld improves significantly after rolling, with reduced ridges and a more uniform surface. Residual stress measurements using the small hole method show a substantial reduction, confirming the effectiveness of the rolling process. **Conclusion:** After nearly a year of development, the machine has proven to be efficient, easy to operate, and environmentally friendly. It not only saves materials and reduces labor but also improves the quality of the weld. With its simple design, flexibility, and advanced performance, it is a promising solution for the stainless steel welding industry. The machine meets safety, environmental, and cleanliness standards and has the potential to become a modern semi-automatic tool for widespread use.

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