Therefore, it is necessary to study effective non thermal aging methods and test methods and scientific basis for the possibility of post weld heat treatment free of welded joints.

Looking at the development in recent years, the domestic pneumatic butterfly valve is developing very rapidly, and more and more manufacturers are optimistic about the valve market. Many years ago, the products were basically introduced from abroad, such as the products in the hardware market, mainly Taiwan products. With the continuous development of domestic production technology, many manufacturers have launched a variety of models of valves to achieve "make in China".