JP3241871B2 - Metal band saw body and metal band saw with excellent fatigue life characteristics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal band saw composed of a high-speed tool steel as a blade material and a body member joined in parallel with the blade material, and more particularly to a metal band saw body material having improved fatigue life. It is.

[0002]

2. Description of the Related Art Metal band saws use a high-speed tool steel blade and an inexpensive low-grade steel body by electron beam welding to save expensive high-speed tool steel. After that, heat treatment adapted to the high speed steel of the blade material, for example, about 11
Quenching at 60 to 1220 ° C and tempering at 540 to 580 ° C are performed. Conventional S50C or AISI for body material
However, when these bodies were heat-treated under the same quenching and tempering conditions as high-speed tool steel, the quenching temperature was too high and the toughness of the bodies was reduced, and the tempering temperature was also high. If too large, the hardness is reduced, sufficient tensile strength cannot be obtained, and the fatigue strength is also reduced.

In order to solve this problem, the present inventors have studied materials capable of securing sufficient hardness under the same heat treatment conditions as high-speed steel, and have examined such materials as JP-B-54-5366 and JP-B-55-32778. New alloys such as those disclosed in Japanese Patent Application Publication No. 61-12022 and Japanese Patent Application Laid-Open No. 2-115353 have been developed and put into practical use.

[0004]

SUMMARY OF THE INVENTION Metal band saws
Generally, a blade material and a body material are endlessly welded and driven by two wheels provided in a band saw machine to cut a non-cut material, mainly a steel material, held horizontally between the wheels. The metal band saw is loaded with tension between the wheels so that the steel material does not bend, and at the same time, receives a repeated bending stress along the wheels when driven. Further, the wheel is inclined with respect to the horizontal, and a twist is applied to the metal band saw according to the inclination of the wheel. Therefore, while driving the metal band saw,
Subjected to tensile stress and bending and torsional stress loads.

In the metal band saw described above,
In recent years, cutting conditions have become increasingly severe due to the increase in difficult-to-cut materials such as super heat-resistant steel and stainless steel and the improvement in cutting efficiency. Have been. Further, in order to reduce the cutting cost, a metal band saw machine is being automated and unmanned, and for this purpose, a stable and long-lasting body material is required. An object of the present invention is to provide a metal band saw body and a metal band saw capable of obtaining a stable and high fatigue life even when heat treatment is performed simultaneously with high-speed steel as a blade material.

[0006]

SUMMARY OF THE INVENTION The present inventor has found that Al (aluminum), which has been recognized as unfavorable because it reduces the fatigue life of a metal band saw body, has been found to exist in certain steels in the presence of N (nitrogen). ) To form aluminum nitride, thereby suppressing the growth of crystal grains during the heat treatment and significantly improving the fatigue life, and reached the present invention.

That is, according to the present invention, C: 0.25% by weight
0.60%, Si: 0.6% or less, Mn: 1.2% or less, Ni: 0.4 to 1.0%, Cr: 4.5 to 6.5
%, One or two of Mo and W are added to Mo + ／ W at 0.1%.
5 to 3.0%, V: 0.03 to 0.50%, Al: 0.
0.3 to 0.20%, N: 0.015 to 0.040%, preferably further contains 0.30% or less of one or more of Nb, Ti and Zr, with the balance being Fe and impurities. Metal band saw body with excellent fatigue life characteristics. In the metal band saw which has been subjected to a heat treatment by joining the metal band saw body in parallel with the blade material made of high-speed tool steel, the crystal grains of the body material forming the metal band saw have an ASTM crystal grain number of 6.
It becomes finer than No. 5 and has a high fatigue life.

[0008]

As described above, one of the most significant features of the present invention is that aluminum is combined with N present in steel to form aluminum nitride, which suppresses the growth of crystal grains during heat treatment and increases the fatigue life. It is in. Since the basic composition of steel greatly affects the fatigue life, the effect of suppressing the growth of crystal grains due to the formation of aluminum nitride and increasing the fatigue life does not clearly appear only by specifying the amounts of Al and N. . Therefore, it is necessary to specify other components to have a composition having a high fatigue life, and further add Al and N. The reasons for the components specified in the present invention are described below.

First, the reasons for limiting the elements for preventing the coarsening of the crystal grains of the body material by quenching high speed tool steel will be described. Al combines with N in steel to form aluminum nitride. Aluminum nitride does not form a solid solution in a matrix even at a high temperature such as quenching of high-speed steel, and prevents crystal grains from coarsening. Al has no effect unless it is 0.03% or more, and when it is excessive, a large amount of nonmetallic inclusions are formed, and when the blade material and the body material are joined by electron beam welding, the inclusions of Al float in a beat shape. Therefore, the upper limit was set to 0.20%.

[0010] N is an essential component for forming nitrides and preventing crystal grains from becoming coarse. In order to ensure the amount of nitride so as to be effective in preventing the crystal grains from coarsening, N should be set to 0.
015% or more is necessary, and if it is too much, a pinhole is formed in the weld bead, so the upper limit was made 0.04%.

Nb, Ti and Zr are nitride-forming elements like Al. However, these elements are strong carbide-forming elements, and the carbides are partially dissolved in the quenching of the high-speed steel, so that they do not have the effect of preventing crystal grains from becoming coarser than nitrides. Therefore, it is necessary to add a complex with Al. Excessive addition causes a tendency for the fatigue strength to decrease due to an increase in the amount of carbide, so the upper limit was made 0.30%. These elements are less effective if one or two or more of them are combined in 0.05% or more. Therefore, the content is preferably 0.05% or more.

Next, the reasons for defining the elements for securing the basic characteristics of the body material of the present invention will be described. C is an essential element for securing the strength and toughness of the body material. Cr, M
It combines with carbide-forming elements such as o, W, and V to precipitate fine carbides during tempering, thereby increasing tempering softening resistance. The amount of C must be determined in balance with the amount of carbide forming elements. To obtain Hv450 or more by tempering, 0.25% or more is required. An excessive amount of C lowers the toughness. %.

[0013] Cr not only enhances the hardenability of the body material,
To form a Cr carbide to increase the tempering softening resistance and improve toughness, so that 4.5% or more is required to increase the fatigue life. However, when Cr carbide is excessive, the softening resistance is conversely lowered, so that the balance of other carbide forming elements is 6.5% or less, preferably 5.
Limited to 5% or less. Ni forms a solid solution in the matrix and contributes to improvement in toughness. Further, even if a fatigue crack is formed, the crack is slow in progress and is an element for preventing brittle fracture, and is an essential element for increasing the fatigue life. To obtain this effect, 0.40% or more is required, and an excessive amount has an adverse effect of insufficient heat treatment hardness. Therefore, the upper limit is set to 1.0%.

Mo and W are effective elements for toughness and abrasion resistance and are also secondary hardening elements. To obtain temper hardness, it is necessary to add one or two of Mo and W. is there. However, since these carbides are apt to agglomerate, an excess thereof causes a decrease in toughness. This gives the Mo equivalent (=
Mo + 1 / 2W) is effective at 0.5-3.0%. V is an element that precipitates as a primary carbide during solidification and is effective in refining crystal grains. In addition, since carbides are hard, they contribute to wear resistance. 0.03% to get these effects
The above is necessary. However, an excessive amount of VC carbide increases the probability of becoming a starting point of fatigue crack generation. Therefore, the upper limit is set to 0.50%.

Mn is added to steel as a deoxidizing agent. M
If n is contained excessively, it impairs the cold workability, so the upper limit was made 1.2%. Si is added as a deoxidizing agent similarly to Mn. An excessive amount of Si tends to increase nonmetallic inclusions and impair the fatigue strength.
And

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
Table 1 shows the chemical components of the steel of the present invention and the comparative steel. Steel ingots of these components were manufactured by melting in an electric furnace, and the steel ingots were processed to a thickness of 1 mm by hot rolling and cold rolling and subjected to an accuracy test. As a certainty test, a heat treatment hardness, a grain size, and a tensile fatigue test were performed. The heat treatment of the test material is the same condition as the normal heat treatment of the high-speed steel SKH59 which is a typical blade material, quenching temperature 1200 ° C, tempering temperature 560 ° C.
And then measured. In the tensile fatigue test, a notched tensile test piece having a depth of 1 mm and a radius of 2 mm shown in FIG. 1 was used. The finish of the notch was a precision finish of JIS 3S. The stress load condition was a partial pulsating tensile load having a minimum tensile stress of 295 N / mm ² and a maximum tensile stress of 980 N / mm ² , and a stress cycle of 10 Hz.

[0017]

[Table 1]

Table 2 shows the results of these tests. Table 2 shows that the comparative steels 1 to 4 in which the amounts of Al and N are small and the grain refinement is not effected by the production of aluminum nitride have a grain size number of ASTM smaller than 5.2 and are coarse grains. I understand. Accordingly, it can be seen that the comparative steels 1-4 have a significantly shorter fatigue life than the inventive steels 8-18. In Comparative Steels 5 to 7, in which the amounts of Ni, V, and Cr are smaller than those of the present invention, the effect of refinement of the crystal grain due to the formation of aluminum nitride is exhibited, but the fatigue life is insufficient because the amounts of Ni, V, and Cr are not appropriate. Is shorter than the steel of the present invention.

[0019]

[Table 2]

[0020] As shown in Table 2, the steel of the present invention was obtained by refining crystal grains by Al and N and optimizing other alloy components.
It has a high fatigue life of 7 × 10 ⁴ times or more. Also,
It is understood that the steels 15 to 18 of the present invention obtained by further adding Nb, Ti, and Zr to the steel of the present invention have an extremely high fatigue life of 11 × 10 ⁴ times or more.

[0021]

According to the present invention, a metal band saw body having fine crystal grains and a long fatigue life can be obtained even if heat treatment is performed under the same conditions as that of high-speed steel as a blade material. Therefore, the metal band saw of the present invention not only lowers the cost of material cutting, but also has high reliability and can be used with confidence in automatic unmanned operation.

[Brief description of the drawings]

FIG. 1 is a diagram of a test piece used for a tensile fatigue test of a test steel.

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 38/00-38/60 B23P 15/28

Claims (4)

(57) [Claims] 1. C: 0.25 to 0.60% by weight, S
i: 0.6% or less, Mn: 1.2% or less, Ni: 0.4
1.0 to 1.0%, Cr: 4.5 to 6.5%, one or two of Mo and W at 0.5% to 3.0% of Mo + 1 / 2W, V:
0.03 to 0.50%, Al: 0.03 to 0.20%,
N: A metal band saw body having excellent fatigue life characteristics, comprising 0.015 to 0.040%, the balance being Fe and impurities. 2. C: 0.25 to 0.60% by weight, S
i: 0.6% or less, Mn: 1.2% or less, Ni: 0.4
1.0 to 1.0%, Cr: 4.5 to 6.5%, one or two of Mo and W at 0.5% to 3.0% of Mo + 1 / 2W, V:
0.03 to 0.50%, Al: 0.03 to 0.20%,
N: 0.015 to 0.040%, Nb, Ti and Zr
A metal band saw body excellent in fatigue life characteristics, characterized in that one or more of the above comprises 0.30% or less, with the balance being Fe and impurities. 3. A blade made of high-speed tool steel and a body joined in parallel with the blade, wherein the body has a C of 0.25 to 0.25.
0.60%, Si: 0.6% or less, Mn: 1.2% or less, Ni: 0.4 to 1.0%, Cr: 4.5 to 6.5
%, One or two of Mo and W are added to Mo + ／ W at 0.1%.
5 to 3.0%, V: 0.03 to 0.50%, Al: 0.
Fatigue life characterized in that the chemical composition and the crystal grain size, which are 03 to 0.20%, N: 0.015 to 0.040%, and the balance Fe and impurities are finer than 6.5 in the crystal grain size number. Metal band saw with excellent characteristics. 4. A blade made of high-speed tool steel and a body joined in parallel with the blade, wherein the body has a C of 0.25 to 0.25.
0.60%, Si: 0.6% or less, Mn: 1.2% or less, Ni: 0.4 to 1.0%, Cr: 4.5 to 6.5
%, One or two of Mo and W are added to Mo + ／ W at 0.1%.
5 to 3.0%, V: 0.03 to 0.50%, Al: 0.
03-0.20%, N: 0.015-0.040%, N
0.30% of one or more of b, Ti and Zr
A metal band saw having excellent fatigue life characteristics, characterized in that the chemical composition and crystal grain size of the balance of Fe and impurities are finer than 6.5 in crystal grain size number.