... 6 subsidiary companies. TongDa Group focuses on the technique of Lost-wax and ... ductile iron, grey iron and so on. Our OEM products are widely used ... the engineers to do research on the variety of the materials ... , Magnetic Particle Inspector, Hardness Tester, Impact Test Machine, and Universal Strength Tester. TongDa ... its competitive prices, reliable quality, on-time delivery and good after-service. ...