| 摘要 |
<p>Pickling is carried out in a vacuum of up to 1 kg/cm2, so that on using H2SO4 for pickling metal, esp. steel, the bubbling effect due to the evolution of H2 is increased; the porous layer of scale on the metal is de-gassed; and the rapid de-gassing achieved by using a vacuum hinders the diffusion of H2 into the surface of the metal. The expansion of the gas bubbles is pref. employed to stir the pickling bath and thus maintain the activity of the bath; and the stirring effect is pref. increased by vacuum-boiling the bath. The exhaust vapours from the pickling bath are pref. compressed and employed for heating the bath. Picling times are reduced. Diffusion of H2 into the metal is prevented. Complex mechanical stirrers for the bath are eliminated. There is no need to move the work-pieces in the bath to improve agitation. The workshop air is not contaminated by fumes. Heat losses are reduced.</p> |
