Analysis of valve ball forming technology

1. The principle of ball spin forming

valve ball forming method (1) casting process This is a kind of traditional processing methods, it requires a set of complete equipment for melting, pouring, also need large workshop and more workers, large investment, process, production process is complex, and pollute the environment, workers technical level of every work directly affects the quality of the product, the sphere of capillary leakage problems have yet to be completely solved, and the rough machining allowance, waste is big, often found in the process of casting defects make the scrap, to increase the product cost, the quality is no guarantee that, this method should not be our factory use. (2) forging This is another method used by many domestic valve enterprises at present, it has two processing methods: One is to cut off the round steel heating forging into a spherical solid blank, and then mechanical processing. Secondly, cutting into circular, stainless steel plate in the large pressure machine mold forming hollow hemispherical blank, and then welded into the ball blank for mechanical processing, this method higher material utilization, but need to be a powerful and furnace press and argon lone welding equipment, investment is expected to need 3 million yuan to develop productivity, this method is not suitable for our factory. (3) the spinning method Metal spinning is an advanced method of less and no chip processing, which is a new branch of pressure processing. It combines the technological characteristics of forging, extrusion, rolling and rolling, etc. It has high material utilization rate (up to 80-90%), saves a lot of processing time (1-5 minutes to form), and the material strength can be doubled after spinning. Due to spin, spin wheel and workpiece small area of contact, metal material in two or three to compressive stress state, easy to deformation, under the power of small, can obtain higher unit of contact stress (up to 25 to 35 mpa), therefore, equipment for light weight, total power needed for small (less than 1/5 of the press, 1/4), has been recognized as foreign valve industry is a kind of energy-saving ball processing scheme, at the same time can also be applied to other hollow axisymmetrical parts processing. Spinning technology has been widely used and developed at high speed abroad. The process and equipment are very mature and stable, and the automatic control of machine, electricity and hydraulic integration is realized. At present, spinning technology in Our country has been greatly developed, has entered the stage of popularization and application.

2. Spinning ball blank technical conditions

According to the production needs of the factory and the characteristics of spinning deformation, the following technical conditions are drawn up: (1) Spinning blank materials and types: 1Gr18Nr9Tr, 2Gr13 steel pipe or steel plate; (2) Blank shape and structure of spinning ball:

3.  Spinning forming 

The effect of ball spinning is different due to the different types of blank selected. After analysis, two schemes are available:

3.1. Plate spin forming method

This solution there are two ways: the first way to flat circular material using the tailstock hydraulic jacking force, press on the outer end face of spherical core mold, together with the spindle rotation, using hydraulic copying equipment, after several spinning contraction deformation gradually attached with a plate was made on the mandrel, get a half a hollow spheres, then cut off excess flash welding groove and processing, after two and a half sphere with argon lone welding butt into the hollow ball blank. The second way is the same with flat blank spin, the difference is that after spinning into a hemispherical, also need to spin out a section of cylindrical semi-finished products, and then the semi-finished blank installed in the semi-spherical mandrel The cylinder segment is gradually shrunk (closed) to form the other half of the ball, and the excess metal material of the closing is attached to the top rod. Finally, the excess part is cut off to obtain a desired overall hollow ball blank. The advantages of this method: the steel plate is easy to come from, the price is lower than that of steel pipe, and the complete hollow sphere can be realized. Compared with the previous scheme of the steel tube necking spinning method, the disadvantages are that two mandrel molds are needed, the spinning process is complex, the required spinning equipment structure and control are more complex, and the equipment cost is higher, but this scheme is still the best one from the perspective of economic benefits and product quality. 3. 2. Steel pipe necking spinning method The scheme is divided into three steps: The first step is to cut the steel pipe according to the size, and then clamp it on the spindle tray of the spinning machine to rotate along with the spindle. With the help of the hydraulic copying device, the wheel spins the pipe billet several times, making it gradually shrink and close, forming a semicircle ball; The second step is to cut off the formed part of the sphere and process the groove; The third step is to weld the two halves of the ball into hollow blanks by argon welding. The advantages of the steel tube necking spinning method are: no mold is needed, and the forming process is simple; Disadvantages are: need to use specific steel pipe, weld, and high cost of steel pipe.

4.  The selection of spinning machine tool

The spinning machine is composed of machine, electric and hydraulic parts. It is an advanced medium machine tool with electromechanical and hydraulic integration. Schematic principle of machine tool. It consists of spindle gearbox and hydraulic ejector, tail seat, wheel rack, bed and other parts. In hydraulic transmission, there is a hydraulic station and its hydraulic system, which provides all the power for the machine tool except spindle rotation. The rotary wheel is a spin profile control device, including profile valve, profile plate, adjustment mechanism and bracket, etc. In the aspect of electric control, advanced computer automatic control is adopted to realize the automation of spinning process