... steel,the thickness is 0.6 mm,firm and durable,no magnetism. Sieve and frame are soldered all around,then make a ... . The testing sieve is processed by use special electrochemistry methods,and coat chrome,so the surface of testing sieve is exact,glazed ... equips full time test personel and special test apparatus,such as microscope,projector,balance and densimeter etc. and it is produced accord with ...