Obiettivo
The main aim of the present research is to research and develop new, low cost alloys for the brazing of steels at temperatures lower than those used when brazing with classical bronzes. The effect of braze composition, base metal, temperature, surface preparation, fluxes and binders on joining is under investigation. Braze metal interfaces are investigated by different methods including transition electron microscopy (TEM), hot stages scanning electron microscopy (SEM), microprobe and ultrasonic (US) testing. Strength and corrosion resistance are investigated as are techniques for ribbon production (including melt spinning). Wires, powders and pastes are under investigation.
The achievements so far include:
The production of new alloys for brazing steels copper (Cu-X-Y-Z) alloys with melting range below 875 C and tensile strength of the brazed joints of the order of 500 MPa for brazing of mild and stainless steels;
copper tin phosphorous (Cu-Sn-P-Y-Z) alloys with melting range below 715 C and joint tensile strength of the order of 150 MPa for large surface brazing or steel to copper brazing;
copper tin (Cu-Sn-A-B) alloy with melting range below 850 C and joint strength of the order of 300 MPa for brazing of titanium stabilised ferretic steels.
Specific fluxes have been developed. Ultrasonic system for nondestructive examination and hot stage scanning electron microscope is in working order. Hot stage SEM, transmission electron microscope and US images of interfaces were produced.
The project has produced materials with some advantages in cost and quality over existing ones. Furthermore, these materials have a good exploitation potential. If the brazing technology becomes more universally accepted, then the research conducted will prove to be of very high value. The brazing technology is relatively new and lacks universal acceptance by industry. An effort to demonstrate its advantages, through more targeted dissemination activities, will, without doubt, help to establish it as a viable alternative to the traditional welding methods.
The brazing technology has a very good potential as a replacement for welding and riveting both in aluminium and steel.
CU-P-SN ALLOY SYSTEM WILL BE INVESTIGATED AS A POTENTIAL CHEAP (SILVER-FREE) ALTERNATIVE FOR BRAZING STEELS AT 700-750 CELSIUS DEGREES. TECHNIQUES OF PRODUCTION OF RIBBON, POWDER (FOR PASTES) AND WIRE IN THESE BRITTLE ALLOYS WILL BE DEVELOPED.
DESIRED JOINT MICROSTRUCTURES ARE TO CONTAIN DISCRETE PARTICLES OF M3P (IN PLACE OF THE CHARACTERISTIC CONTINUOUS EMBRITTLING FILM OF FE2P IF CU-P WERE TO BE USED). THE EFFECTS OF BRAZE METAL COMPOSITION, TEMPERATURE, BASE METAL, ITS SURFACE PREPARATION, FLUXES, BINDER AND BRAZING ATMOSPHERE ON JOINING WILL BE INVESTIGATED. REACTIONS, IN PARTICULAR AT THE METAL/BRAZE INTERFACE, WILL BE STUDIED BY E.G. OPTICAL AND ELECTRON MICROSCOPY, INCLUDING SEM HOT STAGE, AND MICROPROBE ANALYSIS.
BRAZING AND MECHANICAL (STATIC, DYNAMIC, FRACTURE MECHANICS) PROPERTIES OF SELECTED ALLOYS WILL BE DETERMINED. AT APPROPRIATE STAGES, PROPERTIES AND MICROSTRUCTURES OF THESE JOINTS WILL BE COMPARED WITH THOSE OF SILVER BEARING ALLOYS; IN PARTICULAR U.S. NON-DESTRUCTIVE EXAMINATION WILL BE CARRIED ON FOR BOTH SYSTEM TYPES.
Campo scientifico
Argomento(i)
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CSC - Cost-sharing contractsCoordinatore
75139 Paris
Francia