Pfeiffer 博士曾經在一篇文章中稱：“若要探討1886年后無縫在線亞洲日產一區二區:不銹鋼管生產技術的發展，就會發現這一技術沿著兩個方向在發展：一方面是斜軋穿孔和延伸技術的多樣化的發展；另一方面是Heinrich Ehrhardt 研究的水壓沖孔工藝的發展，Ehrhardt于1899年在他的 Dusseldorf的 Reisholz 建立了頂管工廠。”當時，Ehrhardt從曼氏兄弟初期所遇到的困難中吸取教訓，他研制出的水壓沖孔工藝，對管坯質量的要求沒有斜軋穿孔工藝那么高，環式孔型頂管工藝基本上是拔制工藝，因此Ehrhardt軋管工藝是完全不同于曼內斯曼穿孔工藝的另一條途徑。

  在(zai)(zai)19世紀(ji)80年代艾哈(ha)德(de)(de)也曾發(fa)現(xian)圓鋼斜(xie)軋(ya)時工(gong)(gong)(gong)(gong)(gong)件中心發(fa)生(sheng)撕裂，產生(sheng)孔(kong)(kong)腔的(de)(de)現(xian)象，但是他(ta)對這一(yi)(yi)現(xian)象不(bu)夠敏感，后來只好另辟蹊徑，發(fa)展另一(yi)(yi)種生(sheng)產空(kong)心坯的(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)，在(zai)(zai)1891年發(fa)明了水(shui)(shui)壓沖孔(kong)(kong)工(gong)(gong)(gong)(gong)(gong)藝(yi)，比曼內斯曼兄(xiong)弟發(fa)明斜(xie)軋(ya)穿孔(kong)(kong)晚(wan)(wan)了6年，通常所(suo)講的(de)(de)“艾哈(ha)德(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)”（Ehrhardt Process)乃(nai)由(you)水(shui)(shui)壓沖孔(kong)(kong)和(he)頂(ding)管(guan)延(yan)伸兩個工(gong)(gong)(gong)(gong)(gong)藝(yi)過(guo)程組成。1893年初艾哈(ha)德(de)(de)在(zai)(zai)德(de)(de)文《鋼與鐵(tie)》雜志上(shang)發(fa)表(biao)文章稱：水(shui)(shui)壓沖孔(kong)(kong)工(gong)(gong)(gong)(gong)(gong)藝(yi)是生(sheng)產空(kong)心坯的(de)(de)新工(gong)(gong)(gong)(gong)(gong)藝(yi)，它與斜(xie)軋(ya)穿孔(kong)(kong)工(gong)(gong)(gong)(gong)(gong)藝(yi)截然(ran)不(bu)同，它對不(bu)銹鋼管(guan)坯質量的(de)(de)要求(qiu)沒有(you)斜(xie)軋(ya)穿孔(kong)(kong)工(gong)(gong)(gong)(gong)(gong)藝(yi)那么高。采(cai)用頂(ding)管(guan)環頂(ding)制無縫不(bu)銹鋼管(guan)的(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)則要發(fa)明得晚(wan)(wan)一(yi)(yi)些，艾哈(ha)德(de)(de)是在(zai)(zai)1899年在(zai)(zai)杜市的(de)(de)Reisholz地方(fang)建立(li)Rheinmetall工(gong)(gong)(gong)(gong)(gong)廠時采(cai)用頂(ding)管(guan)環以延(yan)伸沖孔(kong)(kong)坯，由(you)此正式誕生(sheng)了艾哈(ha)德(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)，亦即(ji)頂(ding)管(guan)工(gong)(gong)(gong)(gong)(gong)藝(yi)。他(ta)在(zai)(zai)1902年的(de)(de)德(de)(de)國(guo)鋼鐵(tie)工(gong)(gong)(gong)(gong)(gong)程師年會上(shang)發(fa)表(biao)論(lun)文，闡述艾哈(ha)德(de)(de)工(gong)(gong)(gong)(gong)(gong)藝(yi)的(de)(de)技術內涵，并在(zai)(zai)英美兩國(guo)申請了專利。

  艾哈德(de)(de)在(zai)杜市Reisholz 區建(jian)立不銹(xiu)(xiu)鋼管(guan)(guan)(guan)(guan)(guan)廠(chang)與(yu)(yu)德(de)(de)國海軍(jun)部的(de)訂(ding)貨有關，德(de)(de)國海軍(jun)部于(yu)1898年(nian)2月提出一份(fen)無縫不銹(xiu)(xiu)鋼管(guan)(guan)(guan)(guan)(guan)訂(ding)貨單(dan)，由(you)于(yu)數量大，而且要求(qiu)交(jiao)貨時(shi)間緊(jin)，因此海軍(jun)部明確表示位于(yu)杜市的(de)曼內斯曼鋼管(guan)(guan)(guan)(guan)(guan)公司和 Rheinmetall工(gong)廠(chang)都(dou)參與(yu)(yu)生產(chan)，艾哈德(de)(de)原來(lai)采用穿孔和熱拔相結(jie)合的(de)辦法生產(chan)鋼管(guan)(guan)(guan)(guan)(guan)，他接受這份(fen)訂(ding)單(dan)后(hou)，就在(zai)Reisholz建(jian)立不銹(xiu)(xiu)鋼管(guan)(guan)(guan)(guan)(guan)廠(chang)，在(zai)水壓沖孔工(gong)藝(yi)(yi)的(de)基礎上添加空(kong)心(xin)坯延伸工(gong)藝(yi)(yi)即采用頂管(guan)(guan)(guan)(guan)(guan)坯的(de)頂管(guan)(guan)(guan)(guan)(guan)工(gong)藝(yi)(yi)，于(yu)是誕生了(le)完整的(de)艾哈德(de)(de)工(gong)藝(yi)(yi)。