SHANGHAI, July 4 (Reuters) - U.S. semiconductor wafer maker AXT Inc (AXTI.O) said on Monday it would seek permits to keep exporting gallium and germanium substrate products from China, after Beijing abruptly imposed export controls on the metals key to chipmaking. California-headquartered AXT, which has manufacturing facilities in China, said its Chinese subsidiary Tongmei would immediately proceed to apply for the permits. "We are actively pursuing the necessary permits and are working to minimize any potential disruption to our customers," said AXT Chief Executive Officer Morris Young. China's commerce ministry said on Monday it would control exports of eight gallium...