Tham khảo tài liệu 'process selection - from design to manufacture episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 224 Selecting candidate processes Infrared Brazing IRB uses quartz-iodine incandescent lamps as heat energy. For joining pipes typically. Diffusion Brazing DFB braze filler actually diffuses into the base metal creating a new alloy at the joint interface. Gives a strong bond of equal strength to that of the base metal. Braze welding base metal is pre-heated with an oxyacetylene or oxypropane gas torch at the joint area. Brazing filler metal usually supplied in rod form and a flux is applied to joint area where the filler becomes molten and fills the joint gap through capillary action see . Filler metal can be in preforms wire foil coatings slugs and pastes in a variety of metal alloys commonly the alloys are based on copper silver nickel and aluminum. Flux types borax borates fluoroborates alkali-fluorides and alkali-chlorides for brazing aluminum and its alloys in powder pastes or liquid form. Economic considerations High production rates possible using FB and IB but low with TB. Cycle times vary. Long for FB and DFB short for TB. Very flexible process. Large fabrications may be better suited to welding than brazing. Economical for very low production volumes. Can be used for one-offs. Tooling costs low. Little tooling required. Equipment costs vary depending on process and degree of automation. Low for TB high for FB. Direct labor costs low to moderate. Cost of joint preparation can be high. Finishing costs moderate. Cleaning of the parts to remove corrosive flux residues is critical. Typical applications Machine parts Pipework Bicycle frames Repair work Cutting tool inserts Design aspects All levels of complexity. Joints should be designed to operate in shear or compression not tension. Typical joint designs using brazing lap and scarf in thin joints with large contact areas or a combination of lap and fillet. Fillets can help to distribute stresses at the joint. Butt joints are possible but can cause stress concentrators in bending. Lap joints should have
