For the sake of fulfilling the increasing demands on high-pressure vessels

and discussing further on the techniques in their manufacture

we started the research works since the end of 1956. The first mission of our works was to use cast-steel instead of forged steel as the construction material for high-pressure vessels. To do this

we had to prove such possibility both theoretically and experimentally. The second mission was to apply the theory of plasticity of metals to autofrettage the vessels. Obviously

this process of autofrettage is a well-known means to increase the yield strength of any construction material of plastic metals. However

the application of this principle to a high-pressure vessel is a new subject. Although we knew that the technique of autofrettage has only been discussed theoretically

we did begin our experiments both in laboratorial and commercial scale in 1957. The experimental results were consistent with our mathematical deduction. The stresses along the wall thickness of the vessels were more uniformly distributed after the autofrettage treatment

and the material itself was strengthened. Obviously

there are certain deffects in the cast-steel; the small pieces into which it will break under high-pressures may have considerable killing and destroying damage. Hence in the international literatures

high-pressure vessels made of cast-steel are available only for low pressure purposes

and in some cases are even forbidden to use for pressure vessels. But disregarding the conventional rules given by the literatures

our research workers have succeeded in the manufacture of cast-steel pressure vessels. At present

the approved cast-steel high-pressure vessels are welcome everywhere in China

and in many places

these cheap

good

safe and quick-produced vessels are already put into mass production for industrial purposes.