tailieunhanh - Manufacturing Processes phần 4

đường kính cũng sẽ ảnh hưởng đến cường độ dòng điện. Đối với một tốc độ cố định thức ăn chăn nuôi dây, ngắn hơn điện ra thanh sẽ kết quả trong amperages cao hơn. Nếu thủ tục được thiết lập dựa vào tốc độ thức ăn dây, cường độ dòng điện kết quả xác minh rằng các phần mở rộng điện cực thích hợp đang được sử dụng. | ARC WELDING 13-31 Fig. FCAW and GMAW equipment. wire feed speed WFS since electrode extension polarity and electrode diameter will also affect amperage. For a fixed wire feed speed a shorter electrical stick-out will result in higher amperages. If procedures are set based on the wire feed speed the resulting amperage verifies that proper electrode extensions are being used. If amperage is used to set welding procedures an inaccurate electrode extension may go undetected. Self-Shielded and Gas-Shielded FCAW Within the category of FCAW there are two specific subsets self-shielded flux core arc welding FCAW-S Fig. and gas-shielded flux core arc welding FCAW-G Fig. . Self-shielded flux cored electrodes require no external Fig. Self-shielded FCAW. Fig. Gas-shielded FCAW. shielding gas. The entire shielding system results from the flux ingredients contained in the tubular electrode. The gas-shielded variety of flux cored electrode utilizes in addition to the flux core an externally supplied shielding gas. Often CO2 is used although other mixtures may be used. Both these subsets of FCAW are capable of delivering weld deposits featuring consistency high quality and excellent mechanical properties. Self-shielded flux cored electrodes are ideal for field welding operations for since no externally supplied shielding gas is required the process may be used in high winds without adversely affecting the quality of the weld metal deposited. With any gas-shielded processes wind shields must be erected to preclude wind interference with the gas shield. Many fabricators with large shops have found that self-shielded flux core welding offers advantages when the shop door can be left open or fans are used to improve ventilation. Gas-shielded flux cored electrodes tend to be more versatile than self-shielded flux cored electrodes and in general provide better arc action. Operator acceptance is usually higher. The gas shield must be protected from .