艾哈德(Ehrhardt)吸取曼氏兄弟发明斜轧穿孔工艺的初期教训 ,另辟途径 ,研制出水压冲孔工艺。艾哈德式无缝钢管生产过程由冲孔(水压或机械)和顶管两工序组成。采用艾哈德轧管工艺的第一套顶管机组安装在北美大陆。 Ehrhardt learned the initial lessons learned by Man’s Brothers from the process of piercing and piercing the pier by piercing, and developed another way to pierce the pier by pressure. Erhardt seamless steel pipe production process by the punching (hydraulic or mechanical) and pipe jacking two processes. The first set of pipe jacking with Ehru tube rolling process installed in the North American continent.