Transient responses of temperature and penetration to a step change in welding conditions were investigated using FEM calculation of three-dimensional heat conduction and TIC welding of mild steels. Correlations between welding parameters and transient response of temperature and penetration were clarified through the comparison of experimental results with calculated ones. In addition, the temperature distribution and heat flow in the workpiece were also analyzed, from which the main factors of welding parameters dominating the transient response were discussed. Temperature and penetration showed different behaviors to a step change in welding parameters, and their transient responses were characterized by their variation rates from the former quasi-state to later one. With a step change in welding velocity, the characteristics of transient response of temperature showed identical behaviors regardless of the variation of step change and heat input. The same response was also observed in the transient change of penetration. The main factor dominating the transient response to the step change in welding velocity was the heat flow direction. The transient response to a step change in welding current or heat input showed the different characteristics depending upon the variation of heat input, which was caused from the heat flow rate in the workpiece.
Essentially, it is impossible to braze graphite with copper filler metal because no wetting occurs. However, when the graphite is combined with iron in copper brazing, the iron base metal dissolves in molten copper. Simultaneously, the dissolved iron is deposited as columnar Fe/9-6%Cu/1.4-1, 6%C alloy phase from the graphite base material interface at a ocnstant brazing temperature-that is, the "dissolution and deposit of base metal" takes place. By placing the iron foil insert between both graphite base materials, therefore, the columnar phase is deposited from both graphite boundaries toward the foil during heating. As a result, both graphite base materials are united by the columnar phase through the iron foil insert. In the same way, the graphite-to-molybdenum or -tungsten joint can he produced. The shear strength of the graphite-to-graphite joint at 298K was about 32MPa. Further, in the 4-point bending tests at elevated temperature, the flexural strength of the graphite-to-graphite joint was 35-40MPa over temperature ranges from 298 to 873K.
Fusing treatment and press-sintering process of the thermal sprayed coatings have been applied conventionally to improve the wear properties of the ocating. However, it is restricted in application in spite of many advantages of this coating caused by the lack of fundamental data. The purpose of this investigation is to examine the effect of the strengthening treatment on the wear resistance of thermally sprayed Nickel-base self-fluxing alloy. Two strengthening treatments were conducted to sprayed coatings, namely, normal fusing treatment and press-sintering treatment. Dry-sliding wear test were carried out under the conditions of the four types of final load. The wear resistance of each specimen was evaluated by the specific wear which was obtained by measuring the wear trace's width. The results obtained are summarized as follows: 1) An adequate correlation was observed between wear resistance of sprayed coating and both porosity in the coating and macro hardness of the coating, that is, wear resistance was improved by decreasing the porosity and by increasing the macro hardness, respectively. 2) The strengthening treatment to the coating was effective to decrease the porosity and to increase the macro hardness. The change of these factors suggests that it is important to strengthen the cohesion of particles deposited to improve the wear resistance of the coating.
The deposit characteristics of ceramic powder sprayed onto a substrate by the gas tunnel type plasma spraying apparatus were studied, and it was found that the special spraying distance L* can be determined by the deposit characteristics. The relation between the deposit characteristics and the coating quality such as the Vickers hardness and porosity was discussed and it was clarified that the special spraying distance L* governing deposit characteristics corresponded to the critical spraying distance Lc which indicated the largest distance in order to obtain the good coating quality.
Copper to copper lap joint was made by the resistance heating apparatus by which heating and pressure was applied simultaneously. The copper plate was pre-soldered and the alloyed layer was pre-formed by using Pb-50Sn solder. Tensile test of the joints was carried out at room temperature after heat test at 150°C or 250°C for 1000h, heat cycle test from -55°C to +150°C by 1000 cycles or salt spray test at 35°C for 1000h. All of these joints were fractureed at the base metal, copper. The strengths of the joints were as those of the joints which were brazed by using BAg-6. Although the joints made by press-soldering were heated at 150°C or 250°C the thickness of the alloyed layer was constant.
A new algorithm for perimeter measurement for a binary image has been developed. The adjacent two horizontal lines in the image are scanned simultaneously in this algorithm, therefore it is named as DLS(Dual Lines Scanning) method. Its performance is very fast, so suitable for real time measurement, and also its construction is so simple that hardware design is easy. It is proved that the accuracy of measurement in this method increases by employing rectangular pixel with large vertical-horizontal ratio through experimental analysis. This fact is opposed to the intuitive common sense, then the consideration is made on that cause. The simulation is also made on the characteristics of measurement for the simple figure image. As the conclusion, this algorithm is very useful for industrial application, especially for measuring moving objects because of the high-speed and simple configuration.
In electron beam welding, it is very important to set focal position of beam on work piece appropriately. However, it is very difficult to set one accurately in case of complex joint geometry. New beam focus detecting system have been developed as part of intelligent welding system for electron beam welding. When electron beam is irradiated on work poece, backscattered electron, thermoelectron, secondary electron, ion or X-ray emitted from work piece are observed. Among these, thermoelectron is much affected with surface condition of a work piece. That is, as soon as the surface melted, thermoelectron increased rapidly. The results obtained are as follows. 1. In case that the condition of beam convergency on work piece is shifted from out of focus to in focus, signal of thermoelectron shows peak value when beam focal position coincide with the surface of work piece. 2. It is possible to obtain high S/N ratio by employing positive collector bias by which thermoelectron gathered easily to the collector. 3. The detecting accuracy is within ±1% in the case that ab factor is 1.0.
The restraint weld cracking test was conducted to investigate the hydrogen cracking in duplex stainless steels which contain various ferrite/austenite ratio. The gas tungsten arc (GTA) welding was applied with the argon shielding gas containing 10% hydrogen. The effects of preheating or post weld heat treatment (PWHT) on the hydrogen cracking were also tested. The hydrogen cracking occurred in the weld metal with the ferrite ratio higher than 60% using the 10% hydrogen containing shielding gas under the severe restraint condition. The higher ferrite ratio of weld metal produced larger amount of diffusible hydrogen bacause the hydrogen can dissolve in the austenite phase. It was effective for the prevention of cracking to apply the preheating at 473K of the solution treatment at 1373K or to reduce the ferrite ratio by the adjusting the nickel and nitrogen content in the weld metal.
This paper deals with singularity of residual stress produced in edge-bonded rectangles of dissimilar materials using a theory of eigen value and numerical analysis of boundary element method. It was clear that the singularity of residual stress field is the same as that of mechanical field from connecting stress functions of Muskhelishvili with a theory of eigen function. The method of calculating the singularity of rectangles bonded by diffusion bonding was proposed by using similar law and numerical analysis. It was shown that the residual stress distribution of bonded dissimilar materials was more important than the singularity of those for investigating reasonable combination of materials or estimating a joint-strength of dissimilar materials.
Parallel gap resistance welding of Ag plated 0.18 mm diameter oxygen free copper wires to solder plated prined circuit boards (P/B) was investigated. Results obtained are summarized as follows. (1) Proper electrode force of weld condition is selected; the electoode force 2.5 kgf (24.5N, at the start of current on) and the maximum electrode force 2.8 kgf (27.4N). (2) Opteimum Thikness of Solder plating is 15-35μm. (3) Proper width of the Patterns is 0.8 mm (tolerance±0.1mm). (4) Electrode material of Cu-W (Cu 30%, W 70%) has seven times longer life than Mo in the number of tolerable continuous welding points. (90°peel welding strength is over 0.3 kgf (2.94N))
Bonding of Al2O3 coated with Cu2O+Cu obtained by vacuum vaporized deposition of Cu in O2 flow to steel using Ag-Cu-Ti brazing filler metal was proposed and its joint properties were investigated. Spreadability of Ag-Cu-Ti brazing filler metal to Al2O3 coated with Cu2O+Cu was investigated in a vacuum furnace in comparison with no treated Al2O3. Metallurgical joint properties of bonding of Al2O3 to steel (29Ni-16Co steel) using this proposed method were observed with XPS analyser. From spreadability test, it was found that excellent spreadability of Ag-Cu-Ti brazing filler metal to Al2O3 was obtained in Cu2O+Cu coated Al2O3. XPS revealed that joint fracture occured in Ag-Cu layer containing TiO2, Cu2O, CaO and TiO2, Cu2O existed at bonding interface of Al2O3. It was suggested that joint properties were affected with Ag-Cu layer containing TiO2, Cu2O, CaO and bonding was due to oxide reaction between TiO2, Cu2O in Ag-Cu layer and Al2O3 containing SiO2, CaO fluxing oxides.
Bonding of Al2O3 coated with Cu2O+Cu to steel using Ag-Cu-Ti brazing filler metal was conducted in a vacuum furance and joint strength between 96%, 99% Al2O3 and 29Ni-16Co, 13Cr, 18Cr-8Ni steel was investigated in comparison with conventional Ag-Cu-Ti method, Joint strength (shear strength) was evaluated in relation to position of fracture at joint strength test and calculated thermal stress of joint after bonding. Main results obtained are as follows. (1) Position of fracture at joint strength test was in Al2O3 when thermal stress (tension) in Al2O3 was high such as Al2O3/13Cr, 18Cr-8Ni steel joint and in brazing filler metal when thermal stress (tension) in Al2O3 was low such as Al2O3/29Ni-16Co steel joint for both bonding methods. Average value of joint strength indicated high value when position of fracture was in brazing filler metal. Coefficient of variation indicated low value and Weibull shape parameter indicated high value when position of fracture was in brazing filler metal which had no brazing defect. Al2O3/29Ni-16Co steel joint was excellent for bonding combination. (2) Excellent joint properties (average value of joint strength, coefficient of variation, Weibull shape parameter) were obtained at Cu2O+Cu+Ag-Cu-Ti bonding method for Al2O3/29Ni-16Co stell joint. 96% Al2O3 was recomended because it had good spreadability of Ag-Cu-Ti brazing filler metal and maximum values of joint properties were obtained.
The influence of the reaction zone thickness in fiber-matrix reaction on the tensile strength of commercially pure titanium, Ti-6Al-4V and Ti-21V-4Al alloys matrix composites reinforced with silicon carbide fiber made by CVD method was investigated. The silicon carbide fiber is called SCS-6, which is provided for Ti matrix by AVCO CO, Ltd. And the effects of various kinds of additives on the growth rate of reaction zone were also examined using Ti-base binary alloys matrices. The tensile strength of these composites decreased with the increase of the reaction zone due to heattreating reaction, but the strength was not reduced while the thickness of reaction zone was up to about 1μm. Concerning this fact, the fracture mechanism of the reaction zone was discussed based on the circumferential notch analysis proposed by Irwin. The Ti-base binary alloys matrix composites containing Al, V, Me and Cr up to about 30 at%, and Zr and Sn up to about 10 at% could play the most important role in the mechanism responsible for the decrease of the growth rate of the reaction zone with the increase of the additives. This shows that the reaction could be controlled using such additives as mentioned above, which contributes to the stabilization of the composites under severe service conditions, comparing with the case of fibers coated with reaction inhibitors.
In case of bonding materials at room temperature, it is necessary to remove the contamination of oxide-films and absorbed gas from the surface of materials. Such cold solid-phase welding has been studied to joint materials without large deformation. Two processes of cold solid-phase welding were developed under ultra-high vacuum atomosphere and under pure inert gas atomosphere. Under ultra-high vacuum atomosphere, 10-6 Pa, the effect of metal friction for making the clean metal surface, the vacuum level and friction time are discussed. The specimens of copper and aluminum were able to bond each other by rotating 24 rpm for 5 minutes and bonding pressure was 120 MPa. Next, under pure argon gas atomosphere less than 10 ppm oxygen, the effect of radio-frequency discharge time and roughness of material surface are discussed. The copper and aluminum were bonded by 8 and 5 minutes discharge respectively.