这些夹具是必不可少的，以确保最优质的焊接变形和焊接过程中最低。

These jigs are essential to ensure the best quality welds and the minimum of distortion during the welding process.

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第二，也是最重要的一点，很多高强度铝合金不可使用惯用的技术焊接。

Second, and most importantly, many of the strongest aluminum alloys are not weldable using conventional techniques.

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在低温下让钢铁焊接，这原本已是工地中最困难的工作，如今更是几近不可能。

They make working with steel, already the most difficult job on the site, nearly impossible.

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