tailieunhanh - Advanced Welding Processes Episode 1 Part 5

Tham khảo tài liệu 'advanced welding processes episode 1 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Filler Materials for Arc Welding 65 where K a and 3 are constants is the mean current I is the stick-out length and A is the cross sectional area of the conductor. The term a represents arc melting whilst the 01I2 A term indicates the resistive heating in the wire extension t DCEP 16mm Extension DCEN 15mm Extension DCEP 6mm Extension - - DCEP 26mm Extension Figure Effect of polarity and electrical extension on the burn-off rate of a basic flux-cored wire. It is obvious from this equation that significant increases in burn-off rate may be achieved by increasing the wire extension and the operating current. b Alloying addition The range of compositions of solid GMAW wires is limited by the technical and commercial difficulties involved in producing relatively small quantities of special compositions. Flux-cored wires can however be modified by minor adjustments in the flux formulation to produce a range of weld metal compositions and operating characteristics. The range of compositions currently available for plain carbon and alloy steels t is similar to that for MMA electrodes with rutile T1O2 based formulations for ease of t Typical burn-off curves which illustrate this relationship will be found in Appendix 3. t The UK and US specifications for flux-cored welding consumables are summarized in Appendix 4. 66 Advanced Welding Processes operation basic CaO high-toughness hydrogen-controlled formulations and metal powder cores for high recovery and low slag formation. It is also possible to extend this technique to produce low-cost austenitic stainless steel or highly alloyed hardfacing deposits from wires with a plain carbon steel sheath. c Slag shielding and support The solidification characteristics of the slag may be designed to enhance the performance of the process. For example a fast freezing Rutile slag may be used to support the weld pool in vertical or overhead welding enabling higher operating currents improved productivity and better fusion .