JPS6353911B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing clad steel that can easily and inexpensively obtain good joint strength. Traditionally, the main manufacturing methods for clad steel are the hot rolling method and the explosion bonding method, but the manufacturing costs of both are high, and the cost required for preparing the joining material increases the price of clad steel, which in turn leads to the production of clad steel. This is hindering the spread of the technology. Recently, the excellent properties of non-ferrous alloys such as Cypronickel, such as resistance to edge seawater corrosion and resistance to marine biological fouling, have been reviewed, and attempts are being made to apply these not only to seawater desalination equipment, which has traditionally been applied, but also to marine structures and ship hulls. There is a movement to
The need to develop these economically viable clad steels is rapidly increasing. Over the past several decades, numerous researchers have conducted research into low-cost cladding steel manufacturing methods in Japan, as well as other major countries such as the United States, France, and Germany.
No new technology had been developed to replace the crimp and explosion bonding methods, and the development of a new manufacturing method suitable for mass production was considered to be an extremely difficult task. Japanese Patent Application Publication No. 1987-1, which was recently developed in Japan.
The new manufacturing method described in 48468 is a technology developed against this background. This new manufacturing method involves inserting a low-melting point metal plate between the base material and the mating material, and then melting and joining only this joining metal (insert metal), a so-called brazing technique. This method is different from the conventional crimping method, explosion bonding method, and overlay method in that it applies . The feature of this manufacturing method is that it is bonded in advance before rolling. Therefore, the bonding method is also dynamic bonding, whereas crimping and explosion bonding are dynamic bonding.
This method has characteristics similar to static joining. For this reason, there is a need to keep the joint surfaces particularly clean, and the new manufacturing method of the above-mentioned patent application also focuses on this method. In other words, in order to keep the bonding interface clean during heat bonding, one or more substances that form hydrides, oxides, and nitrides, such as zirconium foil, are placed in a space continuous with the gap between the bonding surfaces, and The space is enclosed and isolated from the outside air by welding steel plates, etc. Such a method cannot avoid high costs due to the use of expensive materials such as zirconium foil and the welding work of the steel plate clave for atmospheric shielding. Therefore, in order to create a new technology to replace the conventional method,
There is a need to keep the bonding interface clean during heat bonding and to implement a method for blocking it at low cost. The inventors dared to tackle this difficult problem and, as a result of intensive research, developed a technology to implement this outside air blocking method at low cost using molten flux. The present invention involves melting a low melting point metal for joining (insert metal) inserted between the base material and the joining material, or by semi-melting the joining material itself and then solidifying it without using the joining metal. In order to prevent contamination such as oxidation of the joint in the method of joining two materials by using a molten flux, we propose a method in which the joint is shielded from the outside air by using molten flux. interface can be obtained. The flux selected should be one that completely melts during heating for bonding, is stable for long periods of time at high temperatures, and does not generate harmful fumes.
The flux is not limited as long as it satisfies this condition (for example, a flux for hard soldering is applied).
The method of the present invention allows the use of materials such as expensive zirconium foil in the technique of the patented invention described above;
The difficulties arising from both the welding process and the number of welding work steps are solved. The configuration and effects of the present invention will be explained below with reference to the drawings. The figure shows three methods of shielding the joint from the atmosphere during diffusion bonding.
I gave an example. A is when one set of clad steel is manufactured, and B and C are when two sets of clad steel are manufactured at the same time, and both have the same point that the joint is shielded from the atmosphere by molten flux. are doing. The method shown in Figure A will be explained below.
Since molten flux is used for atmospheric shielding, a receiving tray 6 is prepared, and the base material and the joining materials are assembled in this tray. As shown in the figure, the product support table 7 is placed in the tray 6, the laminating material 2 is placed thereon, and the base material 1 is placed thereon. A low melting point metal plate 5 for bonding is inserted between the base material 1 and the mating material 2 as required. Note that a release agent 8 is sprayed between the support base 7 and the laminated material 2. The joint surface of the base material 1 is pre-coated with Ni plating or the like, if necessary. There are shielding frame plates 4 around the base material.
are welded as shown in the figure. A gap is provided between the frame plate 4 and the laminated material 2 to allow a small amount of molten flux 3 to infiltrate by capillary action. The saucer 6 is filled with flux 3 in an amount sufficient to fill the gap between the product support 7 and the frame plate 4 welded around the four circumferences of the base material 1, but not exceeding the bonding interface. Completely shield the bonding interface from the atmosphere. That is, in the present invention, a shielding frame plate is fixed to the four circumferences of the superimposed upper base material to form a slight gap between it and the side edge of the laminated material, and a shielding frame plate is fixed to the bonding interface within this gap. This method is characterized in that the two materials are diffusion bonded by supplying molten flux so that they do not touch and then heating.
In the present invention, the heat treatment method itself is not particularly limited, but a furnace with a non-oxidizing or reducing atmosphere is preferable in order to prevent oxidation of the surface of the base material other than the interface between the laminated material and the base material and the frame plate. After producing a clad steel with good joint strength through this treatment, it is possible to produce a wide and long clad steel by further hot rolling the clad steel. The method shown in Figure C is for carrying out this hot rolling in a state where the steel is assembled into a sandwich, and the two sets of upper and lower clad steels are joined together using a filler at the special diffusion bonding stage to prevent distortion during rolling. This prevents it from twisting and separating. The effects of this method are as follows. First of all, the bonding interface can be kept clean without being contaminated by the shielding flux. This atmospheric shielding by molten flux is a very effective means for preventing defects caused by impurities and inclusions at the bonding interface. The second is related to bonding pressure. It is clear that applying welding pressure during welding is more advantageous in increasing the welding strength; however, as in the method of the present invention, a low melting point alloy plate for joining is inserted between the base material and the mating material. The bonding pressure is especially effective for bonding when melting the bonded materials, or when diffusion bonding is performed by heating the laminated materials themselves above their solidus temperature and below their liquidus temperature to semi-melt them. Therefore, the holding time required for diffusion can be greatly shortened.
In the technique described in the above-mentioned publication, a pressurized slab is also used for this purpose, but in this case, a steel plate melting clave is used as a method of shielding the joint surface from the outside air, and the pressurized slab It was necessary to place it in this creve. Therefore, there have been problems such as the need to increase the size of the clave by the volume of the pressurized slab and the fact that gas generated from the pressurized slab during heating has an adverse effect on the bonding interface. In general, it can be considered that it is preferable in terms of shielding efficiency that the space including the joint interface that requires shielding from outside air be as small as possible. The shielding method of the present invention using molten flux makes it possible to reduce the size of the shielding area, and due to this reduction, it is possible to use the weight of the base material as the bonding pressure without creating a large clave, and further reduce the bonding pressure. Even if an increase in pressure is required, there is no need to build a large clave, making it possible to use a pressurized slab outside the shielded space. As described above, by using the present invention, the above-mentioned problems in the above description of the published publication can be solved. Another very advantageous feature of the present invention is that the number of man-hours required for preparation for joining, such as assembling the base material and the mating material, can be significantly reduced. For example, in the case of hot rolling, it is necessary to completely shield the joint interface from the outside air until the joint is joined by rolling, so it is especially important to firmly weld the four circumferences of the joining surfaces of the base material and the mating material. be. Furthermore, the explosive bonding method also involves the use of explosives, which requires a lot of man-hours to assemble and prepare for safety reasons. In contrast to such methods, the method of the present invention using molten flux can significantly reduce working time and costs. In fact, the technique disclosed in the above-mentioned publication requires expensive and man-hour assembly welding work before diffusion bonding in order to isolate the joint from the outside air, and is also expensive.
The use of Zr foil, etc. is essential. In contrast, the method of the present invention involves welding by simply surrounding the base metal with a frame plate, and the number of welding steps is significantly reduced. As explained above, in the bonding method that uses the shielding method using molten flux, which is easy to implement, the bonding interface is completely shielded from the outside air, so the interfacial diffusion is normal and sufficient, and the base material and the bonding material are are completely joined. The clad steel thus produced can be hot-rolled as necessary.
It is possible to use wide and long clad steel. Examples of the present invention will be shown below. Base material of JIS SM41B with plate thickness of 65mm and plate thickness of 15mm
One side of each of the 90/10 Cypronickel alloy plates is finished smooth by machining, and those surfaces are made of a low melting point alloy for joining with a thickness of 0.26.
Both materials and the pure copper plate were placed so as to face each other with a pure copper plate of mm in diameter interposed therebetween. For these supports, ordinary steel with a plate thickness of 20 mm was used. Next, using the method shown in Figure A, the area to be joined was shielded from the outside air with a flux made of borax and boric acid, and a diffusion bonding process was performed by heating at 1100°C for 1 hour in an Ar atmosphere furnace. In addition, a test material of the same type as above was prepared in which the low melting point alloy for joining was not charged at the interface between the base material and the bonding material, and the two materials were in direct contact with each other, and the method of shielding the atmosphere at the area to be joined as shown in Figure A was used. By heating the composite material at 1120°C for 1 hour to a semi-molten state, it was diffusion bonded to the base material. Two pieces of clad steel were manufactured using this process. In the next process, the support plate used for these connections is welded to the clad steel formed on it.
It was hot rolled in the form of a single piece to a thickness of 20mm. This hot rolling condition is a heating temperature of 700℃ and a rolling pass count of 850~.
14 passes at 740°C, rolling reduction rate of 10% per pass. The shear strength of these clad steels before and after rolling is
The table shows the results of testing using the test method specified by JIS G 0601.

[Table] All clad steels have good bonding strength that exceeds the lower limit of 10 kg/mm ² of shear strength stipulated in the clad steel standard JIS G 3604 before rolling, and It is clear that those after rolling also exhibit the same or even higher bond strength. There was no occurrence of cracking or peeling of the cladding material due to rolling, and it was verified that high-quality wide and long cladding steel can be manufactured simply and at low cost.

[Brief explanation of the drawing]

The figures explain the method of the present invention, where A shows the case in which one set of clad steel is manufactured, and B and C show the case in which two sets of clad steel are simultaneously manufactured, with the base material and cladding materials etc. The mode of arrangement is shown in a longitudinal sectional view. 1... Base material, 2... Composite material, 3... Molten flux for shielding, 4... Frame plate for shielding, 5... Low melting point metal for joining (insert metal), 6... Receiver, 7... Product Support stand, 8... Peeling agent, 9...
...Filling material.

Claims (1)

[Scope of Claims] 1. When joining a steel plate serving as a base material and a metal plate serving as a joining material, a melting temperature lower than the melting point of both materials is created between the surfaces of the base material and the joining material to be joined. A point joining metal is interposed, and these are heated to a temperature higher than the melting point of the joining metal and lower than the respective melting points of both materials to melt only the joining metal, and then solidify. Therefore, if the laminated material and the base material are bonded together, or if the melting point of the laminated material is lower than that of the base material, the laminated materials may be bonded together without the intervening metal for bonding, at the solidus line of the laminated material. Heat the laminated material to a semi-molten state by heating it to a temperature above the liquidus temperature and below the liquidus temperature,
In the method of joining a laminated material and a base material, a shielding frame plate is fixed to the four circumferences of the superimposed upper base material to form a slight gap between the side edges of the laminated material, and this gap is A method for manufacturing clad steel using a special diffusion bonding method, characterized in that the two materials are diffusion bonded by supplying a molten flux to the bonding surface so as not to touch the bonding interface and then heating.