| 摘要 |
<p>A dry-reduced iron powder for coating welding electrodes consists of particles of a rounded shape and low pore volume having a maximum size of 35 mesh U.S.A. Standard (0.50 mm.) and a minimum size of 120 mesh U.S.A. Standard (0.125 mm.) and with an apparent density of 3.3-3.8 g/cm3. The powder is formed from sponge iron which is given a compressive cold working, e.g. by being rolled into strip or pressed into briquets, and thereafter annealed in a protective atmosphere at a temperature of 750 DEG -1200 DEG C. for between 15 minutes and 4 hours to produce limited sintering of the material. After cooling the powder is crushed, milled and sieved to the desired sieve analysis. Alloying elements such as Ni, Mo, Mn or Si may be mixed in with the iron powder before cold-working; an annealing temperature of 1000-1200 DEG C. then being used. Soft annealing may take place after milling to the final sieve analysis.</p> |
