What are the key points for using different stainless steel spheres
The stainless steel sphere casting method is a traditional processing method that requires a complete set of melting, pouring and other equipment, as well as a large factory and many workers. It requires a large investment, multiple processes, complex production technology, and pollutes the environment. The technical level of workers in each process directly affects the quality of the product. The problem of capillary leakage in the sphere cannot be completely solved, and the blank processing allowance is large, resulting in large waste. It is often found that the stainless steel sphere is scrapped due to casting defects during the processing, which increases the cost and quality of the stainless steel sphere. This method is not suitable for our factory.
Stainless steel sphere forging method is another method currently adopted by many valve enterprises in China. It has two processing methods: one is to cut and heat forge round steel into a solid spherical blank, and then perform mechanical processing. The second method is to mold the stainless steel plate that has been cut into a circular shape on a large press to obtain a hollow hemispherical blank, and then weld it into a spherical blank for mechanical processing. This method has a high material utilization rate, but requires a high-power press, heating furnace, and argon arc welding equipment. It is estimated that an investment of 3 million yuan is needed to achieve productivity, and this method is not suitable for our factory's situation.
Stainless steel ball spinning method is an advanced and chip free processing method, belonging to a new branch of pressure processing. It combines the characteristics of forging, extrusion, rolling, and rolling, and has a high material utilization rate (up to 80-90%), saving a lot of processing time (1-5 minutes for forming). After spinning, the material strength can be doubled.
The necking spinning method for steel pipes is divided into three steps: the first step is to cut the steel pipe according to its size, clamp it in the spindle chuck of the spinning machine, and rotate it together with the spindle. The spinning wheel uses a hydraulic profiling device to spin the pipe blank several times, gradually reducing its diameter and forming a semi spherical body; The second step is to cut off the formed spherical part and process the welding groove; The third step is to weld the two hemispheres into the desired hollow spherical blank using argon arc welding.
Due to the small area contact between the spinning wheel and the workpiece during spinning, the metal material is subjected to biaxial or triaxial compressive stress, which makes it easy to deform. With relatively low power, a high unit contact stress (up to 25-35Mpa) can be obtained. Therefore, the equipment is lightweight and requires less total power (less than 1/5-1/4 of the press). It has been recognized by the foreign valve industry as an energy-saving ball processing technology solution and is also suitable for processing other hollow rotating parts. Spinning technology has been widely applied and rapidly developed abroad, with mature and stable processes and equipment.
The technical conditions for spinning stainless steel ball blanks are formulated based on the production needs of our factory and the characteristics of spinning deformation. The following technical conditions are proposed: spinning stainless steel ball blank material and type: 1Gr18Nr9Tr, 2Gr13 steel pipe or steel plate.
