JPH0881739A - Cutting tool for shearing steel sheet - Google Patents

Abstract

PURPOSE: To produce a cutting tool for shearing a steel sheet having wear resistance and excellent in toughness or setting resistance and seizing resistance by specifying the amt. of primary carbides having a dimension of specified value or above, impact value and proof stress. CONSTITUTION: This cutting tool for shearing is formed of a steel having a compsn., e.g. contg., by weight, 0.50 to 1.00% C, 0.10 to 1.50 Si, 0.20 to l.50% Mn, 4.0 to 8.0% Cr, 0.5 to 3.0% Mn, 0.4 to 1.7% V, <=4.5% Ni, and the balance Fe. Then, the amt. of primary carbides is regulated to 1 to 5% by the area ratio of the microstructure, its impact resistance to >=25J/cm<2> and its 0.2 proof stress to >=1700N/mm<2> . This cutting tool is excellent in toughness, in which chipping and peeling are hard to occur and furthermore excellent in wear resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blade used in a shearing machine for cutting a steel sheet.

[0002]

2. Description of the Related Art The blade for shearing a steel plate is selected according to the type of material to be cut (normal steel, stainless steel, high-tensile steel, etc.) and plate thickness, as well as the working conditions such as hardness of the material to be cut. Therefore, SKS3, SKD11, SKD61, etc. have been mainly used. In recent years, the use of stainless steel plates and high-tensile steel plates has been increasing, and among them, the plate thickness of these plates is 3 mm to 16 m.
When cutting a medium plate or thick plate of about m
It has been a problem that wear, seizure and other damages occur early. For cutting steel sheets of this type, SKD1 is usually used.
1, SKD61 is used, but these problems have not been solved, and the quality of the material to be cut is poor, that is, it is necessary to rework such as cutting the sheared surface after cutting, resulting in a decrease in yield and man-hours. In addition to the increase in the number of blades, it causes various inconveniences such as a decrease in productivity due to the exchange of blades.

[0003]

In order to solve these problems, a conventional high-toughness material having a small amount of primary carbide is used for the selection of a conventional cutting material for a cutting tool having a large wear phenomenon such as chipping or peeling. For blades with a large wear phenomenon,
A high hardness material or a material containing a large amount of coarse carbide was used. However, the wear phenomena of these blades cannot always be classified as described above, and toughness and wear resistance are contradictory properties, and it has been difficult to achieve both at the same time. The inventor examined the force acting on the blade edge portion at the time of shearing as to whether the shearing blade cannot achieve both the wear resistance and the toughness, and as a result, obtained the following findings.

FIG. 1 shows a schematic view of the force acting on the shearing blade. (A) of the upper blade (movable blade) that descends when cutting
Since the forces of μFu and μPu act on parts (B) and (B), respectively, the wear on these parts becomes significant (μ:
Friction coefficient between blade edge and material to be cut, Fu: lateral force acting on blade edge, Pu: shear load). Further, the larger the μFu acting on the (A) portion, the larger the tensile / compressive stress acting on the side surface of the blade, resulting in fatigue due to insufficient strength.
The timing of chipping and peeling due to insufficient toughness becomes earlier. From this, the smaller the force acting on the cutting edge portion, μFu, μPu, the more early wear can be suppressed (at this time, the lateral force Fu and the shear load Pu are values unrelated to the material of the cutting edge portion, and the shearing machine Depends on the specifications). That is, it was found that reducing the friction coefficient μ between the cutting edge and the material to be cut improves the life of the cutting tool.

An object of the present invention is a steel plate having wear resistance, excellent toughness such as chipping and peeling, or seizure resistance, and particularly suitable for cutting a middle plate or a thick plate material having a plate thickness of about 3 mm to 16 mm. The present invention provides a shearing blade.

[0006]

In order to suppress the wear of the cutting edge portion in the shearing of the steel sheet as described above, the inventor of the present invention can reduce the friction coefficient between the cutting edge portion and the material to be cut. Further investigation was conducted based on the knowledge that the life of the cutting tool can be improved. As a result, among the blades that have been conventionally used, a blade having a large amount of primary carbides such as SKD11 has not only 10% or more of coarse primary carbides, but also has a significantly poor impact value, and thus was used as a shearing blade. In this case, the cutting edge may be chipped or peeled off early. On the other hand, when the same material is used to reduce the hardness for the purpose of imparting toughness, the wear of the matrix progresses preferentially,
It was found that primary carbides were present in the worn matrix in a protruding state.

When the cutting operation is continued in such a state, the protruding primary carbides bite into the sheared surface of the material to be cut, and the friction coefficient is rapidly increased. At the same time, the primary carbides fall off to promote wear. Not only that, it is observed that chipping, peeling and the like starting from this are progressing at the same time. On the other hand, in the case of blades such as SKD61 in which primary carbides are less than 1% and scarcely present, wear and seizure gradually start from the initial stage, and especially seizure between the blade tip and the material to be cut significantly increases the friction coefficient. It was recognized that In order to prevent the increase in the friction coefficient that causes such an early life of the blade, the present invention contains an appropriate amount of primary carbides having a certain standard size, and at the same time, has an impact value above a specific value and a 0.2% proof stress. It has been found that the combination of is effective.

That is, the present invention is a blade for shearing a steel plate, in which primary carbides of 1 μm or more have a microstructure area ratio of 1 to 5%, and an impact value of 25 J / cm ² or more,
A blade for shearing a steel sheet, which has a 0.2% proof stress of 1700 N / mm ² or more. The desirable composition of the shearing blade is C: 0.50 to 1.0 by weight%.
0%, Si: 0.10 to 1.50%, Mn: 0.20 to
1.50%, Cr: 4.0-8.0%, Mo: 0.5-
3.0%, V: 0.4 to 1.7%, Ni: 4.5% or less, and the balance Fe and inevitable impurities are preferable.

The reasons for limiting the blade for shearing a steel sheet according to the present invention will be described below. Primary carbide: 1 to 5% (vol%) Primary carbide enhances the wear resistance of the cutting edge part, and especially primary carbide having a size of 1 μm or more reduces the friction coefficient between the cutting edge part and the steel plate, and at the same time improves the seizure resistance. Is effective for. If the amount of primary carbides of 1 μm or more is less than 1%, the above effect cannot be obtained and 5%
A primary carbide having a diameter of 1 μm or more exceeding 10 μm tends to project when the base of the cutting edge portion is worn, and the coefficient of friction between the cutting edge portion and the material to be cut sharply increases. Is limited to 1 to 5%.

Impact value: 25 J / cm ² or more ( ² mmU notch) The impact value is an important constituent factor for ensuring the toughness of a blade in which primary carbides are appropriately present. Impact value of blade is 2
If it is less than 5 J / cm ² , sufficient toughness cannot be obtained, which may cause chipping or peeling of the cutting edge.
Limit to J / cm ² or more. The desired impact value is 26 J /
cm ² or more. 0.2% proof stress: 1700 N / mm ² or more 0.2% proof stress is important for securing the deformation resistance against tensile and compressive stress acting on the blade side face during cutting,
If the% proof stress is less than 1700 N / mm ^{2, the} settling resistance of the cutting edge is reduced and the wear of the cutting edge becomes significant, so that the cutting edge of the cutting edge is 0.
The 2% proof stress is limited to 1700 N / mm ² or more. A desirable 0.2% proof stress is 1900 N / mm ² or more. Next, the desirable composition and range of the shearing blade of the present invention will be described. C: 0.50 to 1.00% C not only enhances the hardness of the matrix, but also combines with Cr, Mo, V and the like to form hard primary carbides, and not only enhances wear resistance and seizure resistance. It is an important element for obtaining the effect of reducing the friction coefficient between the cutting edge portion and the steel plate by setting the predetermined primary carbide amount. If C is less than 0.50%, the above effect cannot be obtained, and if it exceeds 1.00%, the carbides become coarse and the toughness deteriorates.
It is preferable to set it to 50 to 1.00%. A desirable C range is 0.55 to 0.80%.

Si: 0.10 to 1.50% Si is usually added as a deoxidizer, and also increases temper softening resistance and contributes to strengthening the matrix. If Si is less than 0.10%, the wear resistance and sag resistance are deteriorated, causing early wear of the cutting edge, and if added in excess of 1.50%, the toughness is decreased, so the Si range is set to 0.10. It is good to set to 1.50%. The desirable range of Si is 0.5 to 1.4%. Mn: 0.20 to 1.50% Mn is added as a deoxidizing agent like Si, and is effective in improving hardenability and strengthening the matrix. To obtain the above effect, Mn is added at 0.20% or more,
The addition of more than 1.50% lowers the transformation point and lowers the seizure resistance, so the range of Mn is 0.20 to 1.5.
It is good to set it to 0%. The desirable range of Mn is 0.2-
It is 0.6%.

Cr: 4.0-8.0% Cr forms a solid solution in the matrix to increase the tempering softening resistance and contributes to strengthening the matrix, and at the same time, partly combines with C to form primary carbides. It has the effects of increasing the wear resistance and seizure resistance of the blade and reducing the friction coefficient between the blade tip and the steel plate by forming an appropriate amount of primary carbide. If Cr is less than 4.0%, the above effect cannot be obtained, and if it exceeds 8.0%, the primary carbides become coarse, which causes chipping and peeling of the cutting edge. Therefore, the Cr range is 4.0. It is good to set it to 0 to 8.0%. The desirable range of Cr is 6.0 to 8.0%. Mo: 0.5 to 3.0% Like Cr, Mo improves temper softening resistance, and formation of carbide contributes to wear resistance, seizure resistance, and reduction of friction coefficient. If Mo is less than 0.5%, the above effect cannot be obtained, and if it exceeds 3.0%, the toughness is remarkably deteriorated, so 0.5 to 3.0% is preferable. The desirable range of Mo is 0.7 to 2.0%.

V: 0.4-1.7% V has the effect of combining with C to form high hardness primary carbides, improving wear resistance and seizure resistance, and further refining the crystal grains. Have. Further, formation of an appropriate primary carbide is effective in reducing the coefficient of friction between the cutting edge portion and the steel plate.
If V is less than 0.4%, the above effect cannot be obtained and 1.7%
If it is contained in excess of 0.1%, the toughness will be deteriorated. Therefore, the range of V is preferably 0.4 to 1.7%. The desirable range of V is 0.8 to 1.6%. Ni: 4.5% or less Ni is not necessarily required to be added, but Ni has an effect of forming a solid solution in the base material of the blade to enhance toughness, and can be contained if necessary. However, if Ni is added in excess of 4.5%, the hardness decreases, so even if Ni is added, it is preferable to set it to 4.5% or less. The desirable range of Ni is 1
~ 3%.

With respect to the composition of the above-mentioned blade, the primary feature of the present invention is that the primary carbide has an area ratio of the microstructure of 1 to 5%,
In addition, it is preferable that at least the hardness of the cutting edge satisfies 51HRC to 58HRC, and the alloying elements shown below may be included. W: 1.0% or less, Ti:
0.5% or less, Zr: 0.5% or less, Al: 0.2% or less, Nb: 0.5% or less, REM: 0.01% or less, C
o: 3.0% or less

[0015]

EXAMPLES The present invention will be described below based on examples. (Example 1) Materials having the compositions shown in Table 1 were melted in a high frequency induction melting furnace. The obtained ingot was subjected to hot working to form a flat plate having a cross section of 15 mm × 35 mm, which was used as a test material. Of these, the test material No. 9 is equivalent to SKD61, N
o. 10 has a composition equivalent to SKD11. The following characteristic tests were performed on the above test materials. In each characteristic test, a test piece was cut out from the annealed test material and rough-processed into a test piece. For Nos. 1 to 8, oil quenching at 1025 ° C. was performed, and subsequently, the tempering temperature was adjusted to 500 to 560 ° C. so that the hardness became 57 HRC, and the specimen No. Nos. 9 and 10 were adjusted to the quenching and tempering hardness specified in JIS G4404.

[0016]

[Table 1]

(1) Coefficient of friction The coefficient of friction was obtained by processing a test piece into a test piece having a length of 8 mm and a length of 25 mm, and sliding it without lubrication while pressing the end surface of the test piece against the flat surface of the plate-shaped mating material. The friction coefficient μ was obtained from the frictional force at that time. The mating material is SUS304 and SCM415 (annealed material), and the load is 10 kg.
f, the sliding speed was measured after reciprocating at a speed of 10 m / min for a certain time. (2) Tensile strength A test piece parallel to the longitudinal direction centering on a 1/4 part of a flat plate having a width of 35 mm was sampled to obtain 0.2% proof stress and tensile strength.

(3) Impact Value A test piece parallel to the longitudinal direction centering on a 1/4 part of a flat plate having a width of 35 mm was sampled and subjected to a 2 mm U-notch impact test to determine the absorbed energy. Table 2 shows the characteristics and hardness of the above (1), (2), and (3) and the amount of primary carbides of 1 μm or more obtained from each test material.

[0019]

[Table 2]

From Table 2, the amount of primary carbides of 1 μm or more is 1
Comparative blade No. No. 9 and No. 10 of the present invention are blades. It can be seen that the friction coefficient is larger than those of 1 to 8.
In addition, No. No. 9 has a large impact value, but has a small yield strength and tensile strength. In No. 10, both impact value and tensile strength are lower than those of the blade of the present invention.

(Example 2) A shearing blade was produced from the same test material as in Example 1 and incorporated in a shearing machine to carry out a shearing test. The material to be sheared is SUS304 and SC with a thickness of 6 mm.
A plate of M415 was used. The shear test is defined as the life when the chipping or peeling of the cutting edge occurs, and the time when the cut surface of the material to be sheared due to wear or seizure becomes large or the burr of the cut portion becomes large. Up to C
Expressed in ut number. In addition, the cutting tool in which the above defects were not observed at 6000 Cut was stopped at that time. S in Table 3
The results of shear test of the plate material of US304 and the plate material of SCM415 are shown in Table 4.

[0022]

[Table 3]

[0023]

[Table 4]

From Tables 3 and 4, the comparative blade Nos. No. 9 has a low 0.2% proof stress value and a small amount of primary carbides, and therefore has poor sag resistance and wear resistance. Further, due to surface roughness of the cutting edge due to seizure, unevenness appeared on the sheared surface of the material to be cut. . On the other hand, comparative blade No. No. 10 had a large amount of primary carbides, and chipping and peeling occurred early. On the other hand, the cause of the service life of the cutting tool of the present invention is mainly due to fine chipping, and in some cases, fatigue and wear were observed.

[0025]

The blade for shearing a steel sheet according to the present invention is 1 μm.
The area ratio of the microstructure is 1 to 5% of the primary carbide amount of m or more.
By doing so, it becomes possible to reduce the coefficient of friction between the cutting edge and the material to be cut during shearing, and at the same time, make the impact value 25 J
/ Cm ² or more and 0.2% proof stress of 1700 N / mm ² or more, the toughness is excellent, and the problems of sag, wear resistance and seizure resistance are solved, and the life of the sheared blade of the steel plate is improved. It has become possible to extend it significantly.

[Brief description of drawings]

FIG. 1 is a schematic view showing a force acting on a shearing blade when a steel plate is cut.

Claims (2)

[Claims] 1. A shearing blade for steel plates, wherein primary carbides of 1 μm or more have an area ratio of microstructure of 1 to 5%,
Moreover, the impact value is 25 J / cm ² or more, and the 0.2% proof stress is 17
A blade for shearing a steel plate, which has a strength of at least 00 N / mm ² . 2. C: 0.50 to 1.00% by weight,
Si: 0.10 to 1.50%, Mn: 0.20 to 1.5
0%, Cr: 4.0 to 8.0%, Mo: 0.5 to 3.0
%, V: 0.4 to 1.7%, Ni: 4.5% or less, the balance Fe and unavoidable impurities, and primary carbides of 1 μm or more have an area ratio of the microstructure of 1 to 5%, and Impact value is 25 J / cm ² or more, 0.2% proof stress is 1700
A blade for shearing a steel sheet, which has a N / mm ² or more.