JPS649484B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to fasteners such as bolts and nuts, and more particularly to a fastener fastener made of ceramics and a fastener fastening method suitable for fastening ceramic members. As a method of joining ceramic members together, there is a method of bolting using ceramic bolts. However, as is well known, ceramics is a brittle material, so if it is tightened too strongly or an impact load is applied, localized stress concentration will occur, resulting in damage to the thread groove. Additionally, ceramic parts are generally not easy to process, and dimensional accuracy is low in complex-shaped bolts, etc., and the thread grooves formed also have low dimensional accuracy, which exacerbates the problems mentioned above. There are drawbacks. Other conventional examples include Japanese Utility Model Application Publication No. 57-124612 and Japanese Utility Model Application Publication No. 59-37412. However, the fasteners described in these documents simply cover the threaded part with a soft material or a rigid elastic material and are fastened as is, so the parts with low dimensional accuracy between the threaded parts cannot be filled sufficiently. , which was insufficient in preventing local stress concentration. Therefore, there was a problem in that the joint strength of the fastened portion and the resistance to impact loads were low. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for fastening ceramic fasteners that can increase the joint strength of the fastened part and further improve the resistance to impact loads even if the threaded part has a portion with low dimensional accuracy. . In order to achieve the above object, the present invention provides a member that softens at a higher temperature than room temperature between the screw portions of a male threaded body and a female threaded body that are fastened together, and that is a member that softens by heating and hardening by cooling. By using a fastener fastening method that uses an intervening member that has gone through a hardening process, the intervening member spreads between the threaded parts without any gaps during the heating and softening process, and the subsequent cooling and hardening process improves the bonding strength and impact of the fastened part. It has increased resistance to load. In order to fasten members using the fastener according to the present invention, the fastener is first heated to a predetermined temperature range to soften the intervening member fitted in the thread groove or the like. Then, it is fastened in this heated state, and then cooled. Then, the intervening member will also become hard due to cooling, and a robust connection will be achieved. Also,
During tightening, the intervening member is softened and spreads evenly over the gap between the male threaded body and the female threaded body, and after cooling and hardening, the male threaded body and the female threaded body become tightly integrated. As a result, even if an impact load is applied to the fastener, local stress concentration on the fastener is prevented, the risk of thread groove breakage is eliminated, and the joint strength is greatly improved. It is. A superplastic alloy is suitable for such an intervening member that softens in a temperature range higher than room temperature, but other materials such as an alloy, plastic, gasket, etc. that are soft in the heating temperature range during bonding may also be used. Table 1 shows the composition, elongation, and temperature range showing superplasticity of typical superplastic metals.

【table】

[Table] The present invention will be described in more detail below with reference to embodiments shown in the drawings. FIG. 1 is a side view of a bolt according to an embodiment of the present invention. The threaded portion 1a of the bolt 1 and the back side 1b of the bolt head are coated or lined with a superplastic alloy. FIG. 2 is a sectional view of a nut according to an embodiment of the present invention, and the thread groove 2a of this nut 2 is also coated or lined with superplastic alloy. Note that the bolt 1 and nut 2 are each made of ceramics. There are various methods for lining or coating superplastic materials, and methods for coating superplastic alloys include plating, which is an electrochemical method, thermal spraying, and blast bonding. This internal thermal spraying method is a method in which an alloy is melted using a high-temperature flame (for example, an oxygen-propane flame) or an electric arc, atomized with compressed air, and then sprayed and bonded to a material. The blast bonding method is a method in which a superplastic material powder is blasted onto the surface of a material, and the superplastic flow at that time is utilized to quickly cover the material with the powder by pressure bonding. The coating may be applied only to the contact area between the member to be joined and the coupling bolt or nut, or may be applied to the entire coupling bolt or nut. FIG. 3 is a sectional view showing a state in which the ceramic plates 3, 3 are joined together using the bolt 1 and nut 2. That is, holes are made in the ceramic plates 3, 3, and bolts 1 are inserted through them and nuts 2 are fastened. In this connection, the nut 2 and the ceramic plate 3,
3 must be heated to a predetermined temperature. That is, when heated in this way, the nut 2 and the ceramic plate 3 thermally expand, making it easier to insert and tighten the bolt 1, and the superplastic alloy coated on the surface comes to exhibit a superplastic state, reducing the gap between them. When the temperature drops, the nut 2 comes to strongly engage the bolt 1. Conversely, when removing the nut 2, the nut 2 can be easily removed by heating the nut 2 to a predetermined temperature. When heating the nut 2, it is necessary to adjust the heating temperature to the temperature at which the superplastic alloy is most easily deformed. This prevents local stress concentration at the contact surfaces between the ceramics and ensures uniform It serves to fill the gap. In addition, in the bolt 1 shown in Fig. 1, the back side 1b of the bolt head is also lined with superplastic alloy, so when used for joining as shown in Fig. 3, the surface of the ceramic plate 3 and the back side of the bolt head are lined with superplastic alloy. It also has the effect of making the contact with 1b soft and uniform. FIG. 4 is a sectional view showing a state in which a ceramic plate 4 and a thick ceramic member 5 are connected using bolts 1. That is, a through hole 4a and a screw hole 5a are provided in the ceramic plate 4 and the ceramic member 5, respectively, and the bolt 1 is tightened. Also in this embodiment, the bolt 1 and the ceramic member 5 are firmly joined, and the ceramic plate 4 and the bolt 1
The area between the bolt head and the back side 1b becomes uniformly soft. In this embodiment as well, when tightening the bolt 1, tightening is facilitated by heating the ceramic member 5 in advance to a temperature range that shows the superplastic behavior of the lined superplastic alloy. At the same time, the contact surface exhibits superplastic behavior, preventing the generation of local stress and increasing the bonding strength after the temperature of the ceramic member 5 has decreased. Furthermore, if the ceramic plate 4 is heated, the bolt 1 can be inserted easily. In this embodiment, the thread groove of the threaded hole 5a formed in the ceramic member 5 may also be lined with a superplastic alloy. In each of the above embodiments, the bolt 1 and nut 2 are lined with a superplastic alloy, but the lining may be made of other metals that become soft within a predetermined temperature range, plastics, gaskets, or the like. Furthermore, in the present invention, the material of the ceramics constituting the bolts, nuts, etc. is not particularly limited, and it is clear that various oxides, nitrides, carbides, or compositions of combinations of these can be used. According to the present invention, a method for fastening a ceramic fastener is performed between a male screw body and a female screw body that are fastened.
The method uses an intervening member that softens at a temperature higher than room temperature and has gone through a softening process of heat softening and cooling hardening while being interposed, so that the intervening member can be made sufficiently without any gaps between the threaded parts. Since it is interposed in a pervasive state, it has high bonding strength and high resistance to impact loads, allowing for reliable and strong bonding.

[Brief explanation of drawings]

Fig. 1 is a side view of a bolt according to an embodiment of the present invention, Fig. 2 is a sectional view of the same nut, Fig. 3 is a sectional view of a state in which a ceramic plate 3 is joined, and Fig. 4 shows a different state of joining. FIG. 1... Ceramic bolt, 2... Ceramic nut.

Claims (1)

[Scope of Claims] 1. In a method for fastening a ceramic fastener comprising a male threaded body having a male thread and a female threaded body having a female thread, the threaded portion of the fastened male threaded body and the female threaded body may be heated at a temperature higher than room temperature. A method for fastening ceramic fasteners, characterized by interposing a softening intervening member and passing through a softening and hardening process of heating softening and cooling hardening in that state. 2. The method for fastening a ceramic fastener according to claim 1, wherein the intervening member is a superplastic alloy.