| 摘要 |
Copper-base alloy and stainless steel discs to be brazed are degreased e.g. by soaking in a solution of 4-8 ounces of sodium hydroxide per gallon of water at a temperature of 160-200 DEG F. or by vapour or electrolytic means. Surface oxides are removed from the copper discs by immersing them in a solution of: 2 gallons sulphuric acid, 1 gallon nitric acid, 1 quart water, 1/2 fluid ounce hydrochloric acid at room temperature and from the steel discs by immersing them in a water solution of 40 per cent hydrochloric acid at 185 DEG F. The discs are then washed and dried, or rinsed in water, rinsed through methyl alcohol and stored in methyl alcohol. The discs may be stored in water. One surface of each steel disc is coated by brushing or spraying with a flux of:- potassium hydroxide 1 part, water 91 parts, and the following 9 parts: potassium fluoride 40 per cent, boric acid 30 per cent, sodium borate 30 per cent. A molten salt bath at about 1450 DEG F. containing:- sodium chloride 60 or 45 per cent, potassium chloride 40 or 55 per cent is used to provide the heat for the brazing operation. |
