Metal fusion bonding – Process – With measuring – testing – indicating – inspecting – or...
Reexamination Certificate
1998-12-31
2001-10-16
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
With measuring, testing, indicating, inspecting, or...
C228S104000
Reexamination Certificate
active
06302314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for examining bonded-metal by ultrasonic examination, and more particularly, to the method by which the bonding properties such as a bonding temperature, a bonding strength and the like are examined on the basis of an attenuation amount of the ultrasonic wave through a bonding interface of the bonded-metal.
2. Description of Related Art
A method for joining metals together is a process by which pieces of metals are joined together, it can be classified generally into two categories: a metallurgic joining method which gives energy locally to metals to form an atomic bonding therebetween, and a mechanical joining method which use rivets and bolts.
The metallurgic joining method is further classified into a fusion welding method, a pressure welding method, a brazing and soldering method, a diffusion bonding method.
A process of the fusion welding method is as follows. Firstly, bonding faces of base metals are heated to be fusion condition. While heating, if necessary, filler metals may be added therein. The base metals are then bonded together.
A process of the pressure welding is that a high mechanical pressure is applied to bonding faces of metals, the metals are then bonded together. This pressure welding method is classified into a cold pressure welding method, a friction welding method, an explosive welding method, a ultrasonic welding method and a resistance welding method.
A process of the brazing and soldering method is as follows. Firstly, the brazing filler metals are caused to flow into gaps between bonding faces under a fusion condition. Secondly, the metals are caused to solidify, then being bonded together. In this process, the employed brazing filler metals have a lower melting point than the base metals have.
Further, a process of the diffusion bonding method is as follows. Firstly, pieces of metals are caused to contact closely, a pressure is then applied thereto under a temperature of a melting point or less of the metals so as not to produce plastic deformation. Secondly, the metals are bonded with employing atomic diffusion produced on a bonding interface. This diffusion bonding method is classified into a solid-state diffusion bonding method and a liquid phase diffusion welding method. The former is that pieces of metals are directly contacted closely, then causing elements to diffuse under a solid-state. The latter is that insert metals having a lower melting point is put between pieces of metals, then being caused to be fused momentary and solidified by way of isothermal solidification with employing elimination of diffusion of the specified elements in a liquid phase.
The metallurgic joining method such as the diffusion bonding method, different from the mechanical joining method, enables to save material and to cut man-hour, thereby producing a joint having excellent bonding strength, air tightness and pressure tightness. In contrast, a procedure for bonding metals together is irreversible, it is therefore difficult to bond them together repeatedly after separation of the bonding. Further, there is such problem that the bonding properties, such as strength and fracture toughness, vary largely, depending on a type of deficiency of a bonding interface. A lot of factors cause such flaws.
Accordingly, in the case that the metallurgic joining method such as a diffusion bonding method requires high reliability, whether deficiency exists at the bonding interface or not, is examined after bonding. Several nondestructive examinations such as a radiographic testing, a ultrasonic examination, a magnetic particle testing and a liquid penetrant testing can be applied to the bonded-metals. In the case of mass production of the same bonded-metals, from which a part is sampled and a test specimen with a bonding interface is cut off. A destructive examination such as a tensile testing is then carried out.
However, the metallurgic joining method such as a diffusion bonding method accompanies a local heating and/or cooling of metals. Thus, a heat-affected zone with variation both a micro structure and a mechanical property is liable to be produced on vicinity of the bonding interface. Even if deficiency such as flaws, blowholes and bonding defectives is not detected, the bonding properties such as joining strength and fracture toughness may unfortunately be deteriorated.
In such case, destructive examination can be applied to samples produced on a large scale. However, it can not be applied to samples produced on a small scale such as a plant production, thus there is no method for examining the bonding properties of the bonded-metal. Further, the actual bonded-metal includes both deficiency (such as flaws, voids and bonding defectives) and a heat-affected zone. There is also no method for examining the bonding properties of such bonded-metal with achieving high accuracy.
In order to overcome such problem, for example, a procedure for bonding metals together may be standardized by a manufacturer's manual book. However, the bonding properties depend on many requirements such as design of joint, accuracy, cleanliness, a bonding temperature, a holding time, and a bonding pressure. Further, in the case of having no choice but to carry out the bonding procedure out of doors, it is influenced by a weather condition such as a temperature as well as skill of an operator. To use the manufacture's manual book is not enough to achieve high reliability for such bonded-metal which is used for such portion that requires particular high-reliability.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a method for examining bonded-metal by ultrasonic examination, which enables to estimate the bonding properties such as strength and fracture toughness of the metals bonded by way of the metallurgic joining method such as the diffusion welding method, without destructing the bonded-metal.
Another purpose of the present invention is to provide a method for examining bonded-metal by ultrasonic examination, which enables to achieve high-accuracy of estimation.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, a method for examining bonded-metal by ultrasonic examination, the method comprises a step of measuring an attenuation amount of an ultrasonic wave, the ultrasonic wave being generated by a sending probe and received by a receiving probe through a bonding interface, the sending probe and the receiving probe being disposed on the bonded-metal with putting the bonding interface therebetween, the bonded-metal being bonded under unknown condition, and a step of examining a bonding property of the bonded-metal based on the attenuation amount, with utilizing a relationship between a bonding property and an attenuation amount for standard metal bonded under known condition measured preliminarily.
The attenuation amount of ultrasonic wave through bonded-metal is effected by variation of a bonding property at vicinity of a bonding interface. In the case that the bonding property varies due to heat-history, variation of the bonding property is detected in terms of variation of the attenuation amount of ultrasonic wave through the bonding interface.
By comparing the attenuation amount for actual bonded-metal with the attenuation amount for standard metal bonded under known condition, the bonding property of the actual bonded-metal can be estimated, with utilizing a relationship between a bonding property and an attenuation amount for the standard metal.
Preferably, it may be desirable to select a bonding temperature or a bonding strength as the bonding property. Because, a bonding strength is the most important evaluation item for structures upon which stress act, additionally, a bonding temperature affects exceedingly a bonding strength. Where, the bonding properties mean all properties which affect mechanical prop
Horio Hirotsugu
Nakase Hisao
Daido Tokushuko Kabushiki Kaisha
Elve M. Alexandra
Oliff & Berridg,e PLC
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