The hardest steel does not make a mark.

种坚固 不会留下任何痕迹。

Little wheels of extremely hard steel are also used for cutting glass, and this they do fairly well, though not nearly so well as diamonds.

人们还使用极坚硬轮对玻璃进行切割, 种方法虽然比不上使用金刚石那样理想, 但效果还算不错。

That meant that something that's only 2 inches thick - the walls of that 2-inch strip were hard steel, but in the center was liquid.

意味着只有 2 英寸厚西——2 英寸长条带壁是硬，但中心是液体。

Our best steel chisels are made on the same plan: at the cutting edge they have a thin plate of hard steel, which is supported or backed up by a thicker plate of softer steel.

刀口由坚硬薄片制成, 后面再附上一块更厚软铁。