| 摘要 |
A lower pre-heat block assembly 9 for use with a metal scarfing apparatus 5 is disclosed. The lower pre-heat block assembly has a lower block 38 and an extension 39 engaged upon and in overlying relationship with a front face 46 of the lower block. A gas discharge outlet 56 is defined within the front face of the block. The extension may partially overlie the gas discharge outlet such that a gas discharge orifice 70 is defined in the front face of the block by the extension. The extension includes an upper face 58 which extends forwardly from the front face of the block, and is recessed with respect to an upper face 41 of the block. So constructed, when a sheet-like oxidizing gas flow 82 is passed over the upper faces of the block and the extension, respectively, and as a fuel gas 85 is emitted through the gas discharge outlet, the fuel gas is pneumatically compressed between the oxidizing gas flow and the upper face of the extension such that the fuel gas is substantially uniformly distributed along the longitudinal length of the lower pre-heat block assembly and forms a uniform sheet-like fuel gas flow (90) which underlies and adjoins the sheet-like oxidizing gas flow so as to prevent ambient air from aspirating into the oxidizing gas flow and thereby result in a smooth and uniformly scarfed surface on the metal workpiece.
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