JPH0159338B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a steel belt used for cutting architectural materials such as marble and optical materials such as quartz glass, and more specifically relates to a welded portion of the steel belt. The present invention relates to a method of manufacturing a steel belt that can significantly improve the strength of the steel belt.

[Prior art]

It is well known that a steel belt coated with diamond particles on its surface is rotated at high speed to cut architectural materials such as marble or optical materials such as quartz glass.

This type of steel belt must be able to withstand harsh conditions of use as a cutting tool, and therefore must not only be hard but also resistant to fatigue. In response to such demands, this type of steel belt has conventionally been manufactured in the following manner. That is, a strip-shaped material made of carbon steel is hardened, then its ends are welded to form an endless body, which is then tempered.

As is well known, carbon steel becomes hard when it is hardened, and by tempering the hardened carbon steel at an appropriate temperature, the material becomes sticky while maintaining its hardness. be able to.

[Problems to be solved]

Incidentally, in recent years, the above-mentioned steel belts have also been used to cut electronic component materials such as silicon, germanium, artificial quartz, and the like. Especially IC and LSI
Steel belts, which are used to cut out silicon slices that have been formed, are currently attracting the most attention. In other words, technology in the semiconductor field is progressing extremely rapidly, and in particular, the degree of integration has improved significantly. As the degree of integration increases, it is desired to cut silicon slices as thinly as possible. The belt must be thin in order to cut thin slices.

However, in the manufacturing process of conventional steel belts, as mentioned above, after hardening a belt-shaped material made of carbon steel, the ends are welded to form an endless body. There was a problem in that both end portions, that is, the welded portions, which were in a tempered state, went from an extremely high temperature state to a tempered state, and the composition of that portion became extremely soft. For this reason, if the weld is made thinner, the strength of the welded part will be insufficient, and there is a risk of a cutting accident, so it has not been possible to make the weld extremely thin. On the other hand, with recent advances in semiconductor technology, the demand for cutting thin slices has been increasing, and the development of a thin and durable steel belt has been desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a steel belt that can significantly improve the strength of a welded part and, therefore, can manufacture a thin and durable steel belt. shall be.

[Means for solving problems]

In order to achieve the above object, the present invention involves welding the ends of a strip-shaped material made of carbon steel to form an endless body, annealing at least the welded portion of the endless body, and then annealing the annealed endless body. After the quenching, the quenched endless body is tempered.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

The material for steel belts is so-called SK.
High carbon steel with a carbon content of 0.5 to 0.85% is used.

(1) Welding process Prepare a band-shaped material (annealed material) made of the above-mentioned carbon steel, and by butt-welding both ends of the material, an endless body,
In other words, make it a steel belt.

(2) Annealing process The composition of the welded portion of the steel belt has changed and it has become extremely hard and brittle. Annealing to remove this property from the weld.

A neutral salt furnace is used for annealing. The inside of this furnace is filled with a mixture of potassium chloride and sodium chloride, and this mixture is heated and maintained at 760°C. The welded portion of the steel belt is immersed in this mixed solution. In this case, the entire steel belt may be immersed.

After 20 minutes have elapsed after immersion, the heating of the furnace is stopped while the material is immersed, and the material is allowed to cool naturally. As a result, the welded part is annealed and returned to its pre-weld state. That is, the composition of the welded part becomes the same as that of other parts.

The surface of the weld is then polished and finished.

(3) Hardening process The jig shown in Figure 1 is used for hardening.
This jig has an annular frame 1 and a plurality of reinforcing members 2, 2, . A plurality of posts 3, 3, . . . are provided projecting upward. Further, a hook 4 supporting the jig is fixed to the reinforcing member 2 at the center of the jig.

When hardening is performed, as shown in Fig. 1, a steel belt 5, which is a raw material, is placed on the jig.
Place. At this time, the steel belt 5 is held on the jig by being entwined with the posts 3, 3, . . . Then, the steel belt 5 together with the jig is immersed in the above-mentioned neutral salt bath furnace.

This time, the mixed liquid in the furnace was heated and maintained at approximately 830°C, that is, above the transformation point _A3 of carbon steel. Approximately add the steel belt 5, which is the material mentioned above, to this mixed liquid.
Soak for 120 seconds. As a result, the steel belt 5 becomes austenitic.

Next, the steel belt 5 which has become austenite is pulled up from the neutral salt bath furnace and immersed together with the jig in a cooling tank. The cooling tank is filled with a mixture of potassium nitrite and sodium nitrite, and this mixture is heated and maintained at approximately 260°C. The steel belt 5 is immersed in this mixed solution for about 16 minutes.

By immersing the steel belt 5 in the austenitic state in a cooling tank, the steel belt 5 is cooled and hardened. At that time, since the temperature of the mixed liquid in the cooling tank is relatively high as mentioned above,
The structure within the steel belt 5 undergoes isothermal transformation into acicular bainite. This transformation of the structure into acicular bainite allows the steel belt to exhibit higher flexibility and impact resistance than usual when tempered later.

(4) Tempering Although the tempered steel belt 5 is hard, it has no stickiness and is brittle. Also, residual stress is generated inside, causing deformation. Therefore, the hardened steel belt 5 is sandwiched between the jig shown in FIG. 2 and immersed in a tempering bath.

The jig shown in FIG. 2 is a type of correction tool, and has a circular outer ring 10 and a circular inner ring 11. As shown in FIG. 3, a steel belt 5 deformed by hardening is sandwiched between the outer ring 10 and the inner ring 11, and a plurality of fasteners 12, 12...
Fix by. As a result, the shape of the steel belt 5 is corrected into a circular shape, and the shape is maintained during tempering. The tempering tank, like the cooling tank, is filled with a mixed solution of potassium nitrite and sodium nitrite, and this mixed solution is heated and maintained at approximately 430°C. The steel belt 5 held by the jig shown in FIG. 2 is immersed in this mixed solution for about 20 minutes.

After dipping, the steel belt 5 taken out from the tempering bath is slowly cooled while being held in a jig shown in FIG. As a result, the steel belt 5 becomes sticky while maintaining its hardness, and furthermore, the residual stress is removed and the belt becomes circular.

Steel belt 5 manufactured by the above method
The feature is that the structure of the welded part is the same as that of other parts, and the physical properties such as strength are uniform in all parts.

Figure 4 shows a hardness of 300 measured by Microvitkers hardness tester.
3 is a graph showing the measurement results of the Vickers hardness in the vicinity of the welded part under a load of g. Fourth
Figure A shows the measurement results of a conventional steel belt (finished product), and Figure 4B shows the measurement results of the steel belt manufactured according to this example.

As is clear from the graph shown in FIG. 4A, the conventional steel belt has an extremely soft structure distributed on both sides of the weld center.
On the other hand, in the steel belt 5 manufactured according to this example, as shown in FIG. Therefore, the tensile strength of the steel belt itself is also improved.According to experiments, the tensile strength of the conventional steel belt is 116 to 118 Kg/ ^mm2 , but the tensile strength of the steel belt manufactured by this example is 116 to 118 Kg/mm2. It was 156-158Kg/ ^mm2 .

The difference in the composition of the welded part between the conventional steel belt and the steel belt manufactured according to this example is clear from the photographs shown in FIGS. 5 and 6. 5
As shown in the figure, there are some parts whose composition is clearly different from other parts. On the other hand, in the welded part of the steel belt manufactured according to this example, there are no parts with different compositions as seen in conventional steel belts, and the composition is uniform as shown in Fig. 6. .

As described above, the steel belt manufactured according to this embodiment has uniform strength throughout, making it possible to manufacture a steel belt that is stronger and thinner than conventional steel belts.

〔Effect of the invention〕

As explained above, according to the present invention, after welding the ends of a strip-shaped material made of carbon steel to form an endless body, at least the welded portion of the endless body is annealed, and then the annealed endless body is annealed. Since the quenched endless body is tempered after being inserted, a soft composition is no longer generated in the welded part, and the strength of the welded part is significantly improved compared to the conventional one. As a result, a strong and thin steel belt can be manufactured, and processed materials such as silicon slices can be cut into thinner pieces.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a jig used for hardening, which is one step in the embodiment of the present invention, and FIG. 2 is a perspective view showing a jig used in tempering, which is another step in the same embodiment. , FIG. 3 is a sectional view of the jig shown in FIG. 2, and FIGS. 4A and 4B show the hardness distribution of the welded portion of a conventional steel belt and a steel belt manufactured according to an embodiment of the present invention, respectively. 5 is a photograph showing the metallographic structure of the welded part of a steel belt manufactured by the conventional method. FIG. 6 is a photograph showing the metallographic structure of the welded part of the steel belt manufactured by the method according to the present invention. be. 1: Annular frame, 2: Reinforcement material, 3: Post, 4: Hook, 5: Steel belt, 10: Outer ring, 11: Inner ring, 12: Fastener.

Claims (1)

[Claims] 1. (a) Welding the ends of a strip-shaped material made of carbon steel to form an endless body; (b) Annealing at least the welded portion of the endless body; (c) A method for manufacturing a steel belt, comprising the steps of: hardening the annealed endless body; and (d) tempering the hardened endless body.