METHOD FOR GAS CEMENTATION OF LARGE-SIZED ARTICLES Russian patent published in 1994 - IPC

FIELD: processing large-sized articles. SUBSTANCE: articles are heated, heating time being 0.33-0.44 of diffusion sustaining time at carbon potential of atmosphere 0.1-0.2. Sustaining time is 0.32-0.85 of diffusion sustaining time at carbon potential 0.7-0.8. Then articles are cooled, cooling time being 0.009-0.11 of diffusion sustaining time at carbon potential of atmosphere 1.2-1.3. The process is carried out in atmosphere of nitrogen, natural gas and air during their uninterrupted circulation. Quantity of nitrogen which is fed for all the stages of the process during 1 h is 0.95-1.0 of furnace's volume. Natural gas is fed by main and regulating canals at volumes 0.6-0.7 and 0.3-0.4 respectively. EFFECT: increases working period of articles. 1 tbl