... of manufacturing experience 3.ISO9001 certificate Intelnal combustion engine valve steel standards: ASTM,GB,EN,JINSize:4 ... 7mm 20 years of manufacturing experience ISO9001 certificatiuses: inlet and exhaust valves of cars ,light trucks, mini trucks, ... diesel locomotives, generators ,ships, etc. Internal combustion engine valve steel and high temperature alloy 's Grade Comparision in different states ...