Research On Drawing Process Of CNG Gas Cylinder

High pressure gas cylinder is the main holding container of the high pressure, widelyused in electric power, petroleum chemical industry, light industry, textile, metallurgy,machinery, transportation, mining, pharmaceutical industries and daily life. Due to thehigh pressure and contact corrosive medium it endures during the work, and extremeoperating conditions such as high and low temperature, it is a relatively special equipmenteasy to have an accident. With the increase of car ownership, the promotion of natural gasvehicle not only conforms to our country’s economic development strategy, but also caneffectively relieve the energy shortage and air pollution. On-board compressed natural gascylinder (CNG gas cylinder) is one of the key components of CNG vehicle, its securityhas received great attention from the state and market.High pressure gas cylinder according to the manufacturing process can be dividedinto two categories: drawing bottle and tube-type bottle. Due to quality problem of thebottom of tube-type bottle, the development of the tube-type bottle is limited. But thedrawing bottle, using billet as its raw materials, due to the high product safetyperformance, good sealed performance, high bulk density, is more and more welcomed bythe market. At present, drawing bottle is widely used in Europe and the United States andother advanced countries.Based on the ring dies and roller dies drawing as the basic research object, the ringdies and roller dies drawing technology are both used in CNG gas cylinder drawingforming field, aim at solving the practical problems of CNG gas cylinder drawing in theprocess of production. In this paper, with gas cylinder steel34CrMo4as research object,through the material tensile test, compression test, the dynamic recovery constitutive lawsequations of34CrMo4alloy steel is obtained. Detailed theoretical analysis for CNG gascylinder ring dies and roller dies drawing were applied, which gives the ring dies androller dies drawing force theoretical calculation formulas. Through the analysis for thering dies drawing force, the value range of minimum best blank entry angles to mold aregiven, and this conclusion is verified by finite element numerical simulation. Using finite element software, the ring dies and roller dies drawing numerical simulation analysis isprocessed, the rule of variation of process parameters such as drawing ratio, die-entranceangle, the radius and friction coefficient with the ring dies and the roller dies drawingforce is obtained. the influence of the friction coefficient to the roller die drawing force isstudied, finding that bearing friction coefficient makes a great influence on the axialdrawing force and radial pressing force, the axial drawing force increases with theincreasing of the friction coefficient, the roller radial pressing force decreases with theincreasing of friction coefficient.The mechanics theory of roller dies drawing is studied, the theoretical relationformula between drawing speed point and drawing force is built. By finite elementnumerical simulation, the rule of variation of parameters, such as coefficient of friction,the bottle drawing ratio, slab thickness to diameter ratio changed with the drawing force isobtained. Under the same drawing ratio, drawing force of two passes rolling process islarger than single pass rolling process.Compared various process parameters of the ring dies and roller dies drawing underthe same drawing ratio condition, find that the roller dies drawing force is lower than ringdies drawing force, force of single pass ring drawing process is smaller than two passesring drawing process, and the one of single pass roller drawing process is smaller than twopasses roller drawing process. Through introducing the roller dies drawing technology toCNG gas cylinder manufacturing, carring on the reasonable die arrangement, the bottledrawing die was designed, same with the special drawing equipment and production line.In this paper, the results of the study provides a theoretical basis for CNG gascylinder die arrangement of drawing process and the die design, which has importanttheory meaning and application promotion value to the CNG gas cylinder drawingproduction.