JP2010082773A - Saw wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a saw wire having high tensile strength and large strength for twisting by preventing the occurrence of brittleness by hydrogen generated by electrolysis of water when abrasive particles are fixed by electrolytic plating in a fixed abrasive particle type saw wire. <P>SOLUTION: A core part is made of a metal containing iron having high tensile strength as a main component, and a surface layer part is covered by a metal excellent in hydrogen brittleness-resistance, preferably a stainless steel to prevent hydrogen brittleness. Thereby, the fixed abrasive particle type saw wire attaining high tensile strength and the twisting property are achieved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wire saw wire used in a wire saw apparatus for cutting hard and brittle materials such as silicon ingots, artificial crystals, cemented carbides, magnets, and ceramics, which are wafer materials for solar cells and semiconductors. The present invention relates to a method for manufacturing a fixed-abrasive saw wire to which is fixed.

In recent years, fixed-abrasive saw wires in which fine abrasive grains such as diamond are fixed on the surface of a thin metal wire have begun to be used. This fixed-abrasive saw wire has attracted attention because of its much higher cutting ability than a free-abrasive saw wire that is cut by blowing abrasive grains.

The saw wire is long, such as several tens to several hundreds km, and is required to have high strength, and a hard steel wire is generally used as a base material. Further, a thinner wire is desired in order to make a portion (working margin) removed by processing such as an ingot smaller. Furthermore, since the wire is wound several times on the saw machine, it is inevitable that the wire itself will be twisted. Therefore, the wire must be strong against twisting and must be a high-strength wire that does not break. It is desired.

Further, in the fixed abrasive type saw wire, there are, for example, one in which a non-metallic material such as a resin is used as a bonding medium and abrasive grains are fixed to the wire surface, and another type in which a metal is used as a bonding medium and abrasive grains are fixed. The former saw wire using a non-metallic material as a bonding medium allows a resin mixed with abrasive grains to adhere to the surface of the metal wire by allowing the metal wire to pass through the resin mixed with abrasive grains, which is then cooled and cured. Manufactured. Further, the saw wire using the latter metal as a binder is manufactured by floating abrasive grains in a plating solution and fixing the abrasive grains to the surface of the metal wire together with plating during the plating process. In the case of bonding by the above plating, first, a base metal plating is performed on the metal surface, and then a two-layer plating on which a metal plating containing abrasive grains is applied, or in order to further increase the adhesive strength of the abrasive grains, further metal is applied from above. In general, the plating is a three-layer plating.

Among them, for example, in Patent Document 1, the abrasive grains are fixed by composite electrolytic Ni plating, and a large number of hydrogen bubbles are generated by setting the current density in the composite electrolytic Ni plating tank to be equal to or higher than the limit current density. At the same time, there is a method in which surface irregularities appear by this abnormal plating, and abrasive grains are trapped by these irregularities and hydrogen bubbles to fix the abrasive grains uniformly and firmly in the circumferential direction of the core wire.

However, not only when the current density is higher than the limit current density as in the cited document 1, but even when the current density is lower than the limit current density, electrolysis of water always occurs at the same time. In electrolytic plating, a wire is a cathode, for example, in Ni plating, a Ni metal plate is used as an anode, so that water in the plating solution is decomposed and hydrogen is generated on the surface of the wire as the cathode. If it does so, the hydrogen which generate | occur | produces during electroplating will infiltrate the inside of the wire which is a cathode. In such a wire impregnated with hydrogen, when the stress is applied, the movement of atoms is hindered, so that the strength of the wire is reduced, and particularly weakening against twisting occurs, so-called hydrogen embrittlement occurs. Further, in the plating set to the limit current density or more, the effect becomes more remarkable. The smaller the diameter, the greater the influence of hydrogen embrittlement, and as a result, it is extremely difficult to set the limit current density or more.

Although it is conceivable to carry out at a low current density in order to suppress the generation of hydrogen as much as possible, it takes a very long time to manufacture a long wire of several tens to several hundreds km, so it is manufactured to realize mass production The equipment must be excessive, and as a result, it is inevitable to increase the wire unit price.

Regarding such a problem, it is known to use a stainless steel wire as disclosed in the cited document 2 for hydrogen embrittlement. A stable passive film is formed on the stainless steel surface layer, and even in an atmosphere in which a large amount of hydrogen is generated in the plating process, strength reduction due to hydrogen embrittlement cannot occur.
JP-A-2005-46937 JP2000-71162A

However, when stainless steel wire is used, the effects of hydrogen embrittlement can be prevented. For example, martensitic stainless steel has high strength but poor cold workability, and has a small diameter and a long length required as a saw wire. Is difficult to draw. In general, heat treatment can eliminate work hardening, but the number of steps increases and productivity decreases.

In addition, austenitic stainless steel with excellent cold workability can be drawn, but the strength becomes insufficient and the strength sufficient to withstand the tension in use in a saw machine cannot be obtained. Inevitably, there is a problem that it is not possible to reduce the diameter as desired.

Therefore, in the present invention, in order to realize the adhesion of abrasive grains with excellent productivity, even when the current density during plating is set higher, the wire does not cause brittleness due to hydrogen and realizes high strength. As a result of repeated trial and error, the core part and the surface layer part are clad steel wires made of different metals, the core part is a metal having a high tensile strength, and the surface layer part is a saw wire made of stainless steel. The problem can be solved by providing

Since the saw wire according to the present invention is not affected by hydrogen embrittlement in the plating process, it exhibits an excellent effect that it is strong against twisting and has a high strength that can withstand the tensile strength during use. In addition, since it is not necessary to provide a limit of the limit current density that is concerned about hydrogen embrittlement, it is possible to exert an excellent effect in productivity that a necessary plating thickness can be formed in a short time.

The “metal wire having a high tensile strength” of the core portion of the present invention refers to a metal having a high tensile strength enough to withstand the use conditions in the saw machine. Since the usage conditions vary depending on the saw machine and the setting conditions, it cannot be defined, but generally, the wire quality is generally required to be 3000 MPa or more. Therefore, the present invention is also effective for those having a tensile strength equal to or higher than that and capable of causing hydrogen embrittlement. As a typical configuration, there is a high carbon steel wire represented by a piano wire, for example, as the core portion, and an austenitic stainless steel wire represented by SUS304, for example, as the surface layer portion.

As an example, in the high carbon steel wire used as the core, for example, carbon having a carbon content of 0.6 to 1.0%, preferably 0.7 to 0.8% is generally used. The required strength to be used as a saw wire is obtained, and it is also suitable from the viewpoint of cost, and it can be said that it is an optimal material in the present invention. A metal wire that can be obtained is sufficient.

In addition, the stainless steel forming the surface layer part is less likely to cause hydrogen embrittlement for the purpose of the present invention, and has to be drawn to a length of several tens to several hundreds km, and therefore has good drawing workability. Since it is necessary to be a thing, it is good to use austenitic stainless steel.

The stainless steel forming the surface layer is provided to prevent hydrogen embrittlement, and the thickness may be as thin as possible. Assuming that the metal wire diameter of the core portion is constant, if the thickness of the stainless steel of the surface layer portion is large, the wire diameter as a whole becomes large and the object of the present invention cannot be achieved. Further, assuming that the outer diameter of the saw wire is constant, if the thickness of the stainless steel of the surface layer portion is large, the metal wire diameter of the core portion becomes small and high tensile strength cannot be obtained. Therefore, it is necessary to design the thickness of the stainless steel, which is the surface layer portion, assuming the wire diameter and tensile strength required for the final product.

A billet having a surface layer made of SUS304 is rolled onto a high carbon steel containing 0.8% carbon to obtain a wire having a diameter of 5 mm. A wire with a diameter of 2 mm is obtained from this by a drawing process and a heat treatment (about 1000 ° C.) process. This is subjected to heat treatment for removing work hardening by wire drawing, and then drawn to φ0.14 mm in the final wire drawing. As for the wire after drawing, the high carbon steel wire part which is a core part is φ0.11, and the thickness of SUS304 which is a surface layer part is φ0.015. Next, after the base metal plating is performed, the abrasive grains are temporarily fixed to the metal surface by electrolytic plating with a nickel plating liquid in a state where the diamond abrasive grains are suspended, and further, electrolytic nickel plating is applied to strengthen the adhesive strength. .

A tensile test was performed based on JIS Z2241 and a twist test was performed based on JIS G3522-8.4 (1991) for each of the wire of the present invention thus obtained and a wire manufactured by a conventional manufacturing method with the same outer diameter. Among Examples 1 to 4 according to the present invention, Examples 1 and 2 were subjected to temporary fixation to adhesion strengthening plating of abrasive grains at a low current density (40 A / mm ² ), and Examples 3 and 4 were limited in current limit. Temporary fixing to fixing strengthening plating of abrasive grains was performed at a density equal to or higher than (120 A / mm ² ). For further comparison, Conventional Examples 1 to 4 were carried out, Conventional Examples 1 and 2 were made of hard steel wire (φ0.14 mm), Conventional Examples 3 and 4 were made of stainless steel wire (SUS304 / φ0.14 mm), Conventional examples 1 and 3 were plated at the same current density as in examples 1 and 2, and conventional examples 2 and 4 were plated at the same current density as in examples 3 and 4. The results of various tests are shown in the following table.

According to Table 1, the tensile strength is low in the stainless steel wires (conventional examples 3 and 4), which causes a problem in actual use. However, it can be said that it has strength with no problem under actual use conditions. As for the twist value, as in conventional examples 1 and 2, it can be seen that when the current density is increased, the twist value is extremely lowered. However, Examples 1-4 which are this invention by which the surface layer part was covered with stainless steel were the twist values equivalent to a stainless steel wire.

Sectional view of a typical fixed abrasive saw wire of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fixed abrasive saw wire 2 ... Core part 3 ... Surface layer part (stainless steel part)
4 ... Ni plating layer 5 ... Fixed diamond abrasive grains

Claims (2)

Among the wires used in wire saws that thinly slice a hard material by running a wire wound several times around a plurality of rollers, in a fixed abrasive saw wire to which abrasive grains are fixed,
A fixed-abrasive saw wire in which a core portion and a surface layer portion of a saw wire are clad steel wires made of different metals, a core portion is a metal wire having high tensile strength, and a surface layer portion is made of stainless steel. The fixed abrasive saw wire according to claim 1, wherein the core portion of the saw wire is made of piano wire and the surface layer portion is made of austenitic stainless steel.