JPH0350822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fusible conductor alloy suitable for fusible links.

Conventionally, the fusible conductors of fusible links that protect wire harnesses have mainly been () tin-plated soft copper stranded wire as a fusible conductor, and () tin-plated bimetal (bonded conductor). ), () one using Cu-Fe alloy, and () are used.

Of these, () and () aim to speed up the fusing time near the limit current by utilizing the diffusion of tin and copper (decreasing the melting point), but () to ()
Both have high melting points. Therefore, even if a current near the fusing limit flows, the temperature rises slowly and it takes a long time until the fusing occurs. As a result, the fusible conductor remains in a red-hot state, that is, a high-temperature state, for a long time, and there is a danger that the housing housing the fusible conductor, etc., may melt and burn out, exposing the current-carrying portion, and causing a fire.

On the other hand, if attention is paid to materials with a low melting point, the use of zinc, solder, etc. may be considered, but these materials are unsuitable as they tend to melt and have poor mechanical strength as fusible conductors used in automobiles that run and vibrate.

In addition, β-brass (generally an alloy of 57% copper and 43% zinc) is attracting attention as a material that can solve the above problems. However, β-brass has a large amount of zinc and is therefore difficult to roll, causing stress corrosion cracking (stress cracking) especially during cold working, and dezincing phenomenon in which zinc is eluted in a corrosive atmosphere.

The present invention was made in view of the above problems, and
By adding 0.5 to 3.0% tin to Shiroku brass (40% zinc), which is commonly used for castings, plates, bars, etc., it has excellent fusing characteristics (i.e. current sensitivity) and corrosion resistance.
Moreover, it has been found that a soluble conductor with good workability can be obtained.

The fusible conductor alloy of the present invention can be obtained by adding 0.5 to 3.0% by weight of tin to Shiroku brass, but from the viewpoint of fusing characteristics and workability, the content is preferably 0.8 to 1.5%. In other words, the alloy of the present invention relatively reduces the amount of copper and increases the proportion of β by adding tin to 460°C, and the atomic arrangement of this β-brass changes at around 470°C and the electrical resistance increases. The aim is to utilize the property of rapidly increasing properties without compromising mechanical strength as much as possible. If the amount of tin added is less than 0.5%, the degree of melting point depression will be small and sharp fusing properties will not be obtained, and if it exceeds 3.0%, the mechanical strength will decrease and it will not be suitable for vehicles with vibrations. It becomes less practical.

FIG. 1 is a graph showing the fusing characteristics of the alloy of the present invention and a conventional product, in which the vertical axis represents the time (seconds) required from the red-hot state of the fusible conductor to the time of fusing. As is clear from the figure, the conventional Cu-Fe alloy (described above)
has a faster fusing time than the annealed copper stranded wire product (above),
In addition to being safer, the tin-containing brass of the present invention also has a shorter glow time and excellent fusing characteristics. In addition, the numerical values such as , , etc. in the figure indicate the number of melted pieces when 10 housings each made of thermoplastic synthetic resin (nylon 66 + glass fiber 30%) containing fusible links are used.

In addition, metals such as iron, manganese, aluminum, silicon, chromium, and manganese are added to the alloy of the present invention to improve corrosion resistance and mechanical properties.
It can also be added in a range of 1.0 or less.

FIG. 2 shows an embodiment in which the alloy of the present invention is used as a fusible link. That is, 1 is a housing made of thermoplastic synthetic resin such as polyamide resin or polypropylene, 2 is a cover thereof, and a fusible link 5 composed of a fusible conductor 3 and a female terminal 4 is accommodated in the housing 1. It is becoming more and more common.

The fusible conductor 3 is made by connecting one end of the plate-shaped fusible conductor part 3a made of an alloy of brass and tin to the female terminal 4 by crimping or the like, as described above, and connecting the bent end to the other end. A tin chip 6 is crimped onto the piece 3b by a claw piece 3c.

A current near the fusing limit current flows through the fusible conductor 3, and when the temperature reaches around 400°C, the tin of the chip 6 that is bound and fixed is heated and gradually begins to diffuse. At this time, since the fusible conductor 3 itself is a tin-containing alloy, it has a strong affinity for the chips 6, making it easier for tin to diffuse. Next, when the temperature rises to about 470° C. or higher, the atomic arrangement within the crystal lattice of the β phase undergoes a phase change from aligned to misaligned, resulting in a rapid increase in electrical resistance. As a result, due to the synergistic effect with the diffusion phenomenon of tin in the chips 6, alloying further progresses and the melting point decreases, making it possible to significantly shorten the time from temperature rise to melting.

As explained above, the present invention has 0.5 to 46 brass.
Since it contains up to 3.0% tin, it has better workability and productivity than β-brass, and it contains more β-phase than Shiroku brass, making it an alloy for fusible conductors with excellent current sensitivity. can be provided.

Furthermore, since the time from temperature rise to melting is short, a safer fusible link can be manufactured, and this is further promoted by the combination with tin chips, etc., as shown in FIG.

Furthermore, the addition of tin suppresses the dezincing phenomenon and stress corrosion cracking, which become stronger as the amount of zinc increases, resulting in a fusible link with a long life.

[Brief explanation of drawings]

FIG. 1 is a graph showing the fusing characteristics of the alloy of the present invention and a conventional product, and FIG. 2 is an explanatory diagram showing an embodiment of a fusible link using the alloy of the present invention. 1... Housing, 2... Cover, 3... Fusible conductor, 4... Female terminal, 5... Fusible link, 6... Tin chip.

Claims (1)

[Claims] 1. A fusible conductor alloy characterized by adding 0.5 to 3.0% of tin to 46 brass.