JPH0847710A - Manufacture of cold finished steel bar made of high-speed tool steel - Google Patents

Abstract

PURPOSE:To provide a cold finished steel bar made of high-speed tool steel with which the wear of a die is reduced, also the execution of heat treatment in the middle is unnecessitated, the shortening of the process is possible and which is excellent in straightness. CONSTITUTION:Using a wire 20 having the composition of high-speed tool steel consisting of, by weight, 0.80-1.25% C, <=0.50% Si, $ 0.40% Mn, 3.50-4.50% Cr, 3.00-10.00% Mo, 1.50-11.00% W, 0.90-3.70% V, <=12.5% Co and the balance Fe with impurities, the wire is inductionally heated to 500-700 deg.C with an induction heating device 3. After that, the wire is drawn to a reduction of area of <=30% with a die 5 having a die approach angle of 10-20 deg., bearing length of 1.5-3.5mm and, further, after making the wire into the steel bar having proper length by cutting the wire with a cutting machine 7, the bar is straightened at 300-450 deg.C with a straightening device 9 by utilizing remaining heat.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is used for producing high-speed tool steel polished steel bar used in a wide range of fields such as shafts of various hydraulic equipment and industrial machines, cutting tools such as drills and taps, and the like. The present invention relates to a method for producing a high-speed tool steel polished steel bar.

[0002]

2. Description of the Related Art Polished steel bars are made of hot-rolled steel bars (bars) and wire rods (bar-in coils) that are drawn through a die, cut, or ground.
Further, it is manufactured by combining heat treatments as required, and is a high-grade steel bar having excellent surface quality, uniform dimensional accuracy, uniform material, and good workability.

In manufacturing such a polished steel bar, (i) the cold plastic deformability of the steel is utilized to draw out a steel bar or a wire rod (hereinafter referred to as a wire rod) through a die to obtain good dimensional accuracy. A method of making a drawn and polished steel bar with smooth and bright skin, or (ii) using a centerless bar peeling machine, cutting with a bite,
A method of using a polished steel bar with surface scratches and surface decarburized layer removed, or (iii) a wire rod that has been subjected to drawing or peeling is ground around the periphery with a centerless grinder to obtain good dimensional accuracy and surface texture, and to obtain surface scratches and surface debris. For example, a method of removing a defective surface layer such as a charcoal layer into a polished steel bar is adopted.

Conventionally, when producing a high-speed tool steel polished steel bar through a drawing process using a die, a hot-rolled steel wire rod is used as a raw material, spheroidized, and then passed through a cassette roller die. Then, the steel bar was drawn several times, annealed, and then cut into a fixed length to obtain a steel bar having an appropriate length. The material was bent to some extent by the drawing, so that the steel bar was straightened.

[0005]

However, in the conventional method for producing a high-speed tool steel polished steel bar, the die wear was large, heat treatment was required in the middle, and the straightness was not sufficient. An object of the present invention is to manufacture a high-speed tool steel polished steel bar having a long die life and further excellent straightness without heat treatment in the middle.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is possible to reduce the wear of the die, improve the life of the die, and to perform the heat treatment in the middle. Without, it is possible to shorten the process,
It is an object of the present invention to provide a method for producing a high-speed tool steel polished steel bar, which can further improve the straightness of the high-speed tool steel polished steel bar.

[0007]

A method for producing a high-speed tool steel polished steel bar according to the present invention uses a wire rod having a composition of a high-speed tool steel, heats it to a temperature of 500 to 700 ° C. by induction heating, and then uses a die approach. 30% with a die with an angle of 10 to 20 ° and a bearing length of 1.5 to 3.5 mm
After drawing to the following area reduction rate, further cutting the wire rod into a steel bar of an appropriate length, and then using residual heat, 300 to 45
The feature is that the temperature is corrected at 0 ° C.

In an embodiment of the method for producing a high speed tool steel polished steel bar according to the present invention, the wire having a high speed tool steel composition has a weight ratio of C: 0.80 to 1.25%,
Si: 0.50% or less, Mn: 0.40% or less, Cr:
3.50 to 4.50%, Mo: 3.00 to 10.00
%, W: 1.50 to 11.00%, V: 0.90 to 3.
70%, Co: 12.5% or less, and a high-speed tool steel wire rod composed of the balance Fe and impurities. In the same embodiment, graphite can be used as a die lubricant. Similarly, in the embodiment, polishing may be performed by a centerless grinder after straightening.

The high speed tool steel applied in the method for producing the high speed tool steel polished steel bar according to the present invention includes:
C: 0.80 to 1.25%, Si: 0.50% or less, M
n: 0.40% or less, Cr: 3.50 to 4.50%, M
o: 3.00 to 10.00%, W: 1.50 to 11.0
0%, V: 0.90 to 3.70%, Co: 12.5% or less, a high-speed tool steel wire rod composed of the balance Fe and impurities is used. There is speed tool steel.

Then, such a high speed tool steel wire is used as a raw material and heated to a temperature of 500 to 700 ° C. by induction heating. At this time, if the induction heating temperature is lower than 500 ° C., work hardening cannot be suppressed and residual stress remains, so the load on the die during drawing becomes large and the life of the die is shortened. Therefore, the induction heating temperature is 500 ° C. or higher, more preferably 55 ° C.
The temperature is preferably 0 ° C or higher. Also, the induction heating temperature is 700
When the temperature is higher than ℃, the friction coefficient between the wire and the die during pulling may become too large, which may cause breakage, so the induction heating temperature is 700
C. or lower, more preferably 650.degree. C. or lower.

In this induction heating, the wire having a high-speed tool steel composition has better induction heating characteristics than the austenitic material, and therefore, it can be heated by induction heating with a relatively low frequency and low capacity. Heating up to about 700 ° C., which is about 100 ° C. lower than that of an austenitic material, is sufficient.

Then, after heating the wire having a high speed tool steel composition to a temperature of 500 to 700 ° C. by induction heating, a die having a die approach angle of 10 to 20 ° and a bearing length of 1.5 to 3.5 mm is used. It is used to draw a wire to a surface reduction rate of 30% or less.

At this time, the die approach angle is 10 °
If it is smaller than this, the drawing stress will increase and the load on the die will increase, which will shorten the life of the die,
If the die approach angle is larger than 20 °, the pulling stress will increase and the load on the die will increase and the life of the die will decrease. However, it is not preferable because it may worsen the surface texture after drawing.

The die bearing length is 1.5 mm.
If it is smaller than the above value, the straightness of the drawn wire tends to be lowered, which is not preferable, and the bearing length is 3.
If it is larger than 5 mm, the straightness of the drawn wire is good, but the drawing force is increased, which is not preferable.

Further, when the area reduction rate exceeds 30%, the load on the die becomes large and there is a possibility that the die may be cut off. Therefore, the area reduction rate is preferably set to 30% or less.

In this way, after the wire is drawn using the die, the wire is cut into a steel bar having an appropriate length, and the residual heat is used to straighten at a temperature of 300 to 450 ° C.

At this time, the straightening temperature of the steel bar due to the residual heat is 3
If the temperature is lower than 00 ° C, the straightening property of the steel bar will decrease, so 3
It is preferable to set the temperature to 00 ° C. or higher, and if the steel bar straightening temperature due to the residual heat is higher than 450 ° C., it becomes difficult to obtain the straightness of the steel bar, so the straightening temperature utilizing the residual heat is set to 300 to 450 ° C. By performing such warm correction, it is possible to further reduce the occurrence of distortion, and to reduce the heat treatment deformation when heat-treating after quenching and tempering after forming into taps. It becomes possible to make things.

After the straightening, if necessary, by polishing with a centerless grinder, surface defects such as surface flaws and surface decarburized layer can be removed, and the surface texture is further improved at a high speed. It becomes possible to obtain a tool steel and a polished steel bar.

[0019]

The method for producing a high-speed tool steel polished steel bar according to the present invention has the above-described structure, so that the life of the die is improved and it is not necessary to perform heat treatment in an intermediate step. Since the process will be shortened and since the warm correction using the residual heat is adopted, heating in the middle is unnecessary in this case as well, energy cost is reduced and distortion is reduced, The straightness is further improved, and high-quality high-speed tool steel polished steel bar is produced at low cost.

[0020]

【Example】

[Table 1]

Diameters having the chemical composition shown in Table 1.
1 mm, tensile strength 80 kgf / mm ² , hardness HRC15
As shown in FIG. 1, using the high speed tool steel wire rods of No. 16 to 16 as a raw material, the wire rod 2 of the high speed tool steel composition drawn from the feed coil 1 at the feed position is passed through the induction heating device 3 to generate 5
After heating individually to the target temperatures of 00 ° C, 600 ° C and 700 ° C, they are brought into contact with the die lubricant 4 made of graphite and passed through the die 5 having an approach angle of 18 ° and a bearing length of 3.0 mm. Drawing speed 8.0m /
10%, 20%,
Wires were drawn at different wire drawing rates of 30% and the wire diameter was 6.65 mm
A drawn wire rod having a size of 6.35 mm and 5.95 mm was obtained.

Further, the drawn wire is cut into a fixed length of 4.0 m by a cutting machine 7, and the residual heat is used to make 30
Straightening is performed by a straightening device 9 using a water-soluble straightening oil at a temperature of 0 to 450 ° C., and then a centerless grinder 11 is used.
Polished by.

When the relationship between the working temperature and the deformation resistance (pulling stress) in this high speed tool steel polished steel bar was examined by a greeble test, it was found that the deformation resistance ( It was possible to reduce the drawing stress). However, in the actual drawing process, the coefficient of friction between the wire and the die increases by increasing the processing temperature. Therefore, the drawing temperature is 500 to 700 because of the balance between the deformation resistance and the friction coefficient.
It was confirmed by various experiments that it is preferable to select in the range of ° C.

Next, when the straightness accuracy of the high speed tool steel polished steel bar thus obtained was examined, as shown in FIG. 3, it was found that the processing was performed at a temperature of 500 to 700 ° C. It was confirmed that it is possible to obtain a better straightness accuracy.

Further, when the hardness of the material, the hardness after drawing and the hardness after drawing-correcting were examined at each temperature, as shown in FIG. 4, good results were obtained even in the temperature range of 500 to 700 ° C. It was confirmed that it exhibited a hardness value.

Further, when the residual stress of the obtained high speed tool steel polished steel bar was examined, as shown in FIG. 5, as compared with the cold drawing-cold straightening material, warm drawing-warm straightening (600
The residual stress of the (.degree. C.) material was smaller, and the effect of suppressing the residual stress in warm working was confirmed.

Further, in consideration of use as a cutting tool such as a tap, the high-speed tool steel polished steel bar obtained here was subjected to heat treatment such as quenching and tempering by a conventional method. As shown in FIG. 5, it was confirmed that the hardness hardly changed as compared with the conventional material, and that the high speed tool steel polished steel bar suitable for the working tool such as tap was obtained by the method of the present invention.

Furthermore, when the amount of bending before and after the heat treatment for quenching and tempering was examined, it was confirmed that the higher the processing temperature, the smaller the amount of bending as compared with the conventional material, as shown in FIG.

[0029]

EFFECT OF THE INVENTION The method for producing a high speed tool steel polished steel bar according to the present invention uses a wire rod having a composition of a high speed tool steel and after heating to a temperature of 500 to 700 ° C. by induction heating, a die approach angle of 10 to 10 is obtained. 20 °, bearing length is 1.
Draw with a die of 5 to 3.5 mm to a surface reduction rate of 30% or less, further cut the wire rod into a steel bar of an appropriate length, and then use the residual heat to correct it at a temperature of 300 to 450 ° C. Therefore, it is possible to improve the life of the die, and it is possible to shorten the process because there is no need to perform heat treatment in the middle. The cost can be reduced, the occurrence of strain can be suppressed, and the straightness can be further improved. Therefore, it is possible to manufacture high-quality high-speed tool steel polished steel bar at low cost. The remarkably excellent effect of

In the embodiment, the wire having a high speed tool steel composition has a weight ratio of C: 0.80 to 1.25%,
Si: 0.50% or less, Mn: 0.40% or less, Cr:
3.50 to 4.50%, Mo: 3.00 to 10.00
%, W: 1.50 to 11.00%, V: 0.90 to 3.
70%, Co: 12.5% or less, and a high-speed tool steel wire rod composed of the balance Fe and impurities brings about an effect that a polished steel bar suitable for taps, drills and the like can be obtained. .

Similarly, in the embodiment, by using graphite as the die lubricant, even when the drawing process is performed up to a temperature of 700 ° C., there is no occurrence of tearing or rough skin, and a centerless grinder after straightening. The polishing has the excellent effect that a high-speed tool steel polished steel bar having an even better surface quality can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a line configuration according to an embodiment of a method for producing a high-speed tool steel polished steel bar according to the present invention.

FIG. 2 is a graph showing an example of a relationship between a heating temperature and a pulling stress (deformation resistance) by a greeble test.

FIG. 3 is a graph showing a measurement result of straightness accuracy.

FIG. 4 is a graph showing the measurement results of hardness.

FIG. 5 is a graph showing measurement results of residual stress.

FIG. 6 is a graph showing the measurement results of hardness after heat treatment.

FIG. 7 is a graph showing the results of measuring the amount of bending before and after heat treatment.

[Explanation of symbols]

 1 Feeding coil 2 Wire material of high speed tool steel composition 3 Induction heating device 4 Dice lubricant 5 Die 7 Cutting machine 9 Straightening device 11 Centerless grinder

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C22C 38/24

Claims (4)

[Claims] 1. A wire rod having a high-speed tool steel composition is used, and after heating to a temperature of 500 to 700 ° C. by induction heating, a die approach angle is 10 to 20 ° and a bearing length is 1.
Draw with a die of 5 to 3.5 mm to a surface reduction rate of 30% or less, further cut the wire rod into a steel bar of an appropriate length, and then use the residual heat to correct it at a temperature of 300 to 450 ° C. A method for producing a high-speed tool steel polished steel bar, which comprises: 2. A wire rod having a high-speed tool steel composition, in a weight ratio,
C: 0.80 to 1.25%, Si: 0.50% or less, M
n: 0.40% or less, Cr: 3.50 to 4.50%, M
o: 3.00 to 10.00%, W: 1.50 to 11.0
The method for producing a high-speed tool steel polished steel bar according to claim 1, wherein the high-speed tool steel wire rod comprises 0%, V: 0.90 to 3.70%, Co: 12.5% or less, and the balance Fe and impurities. . 3. The method for producing a high speed tool steel polished steel bar according to claim 1, wherein graphite is used as a die lubricant. 4. The method for producing a high-speed tool steel polished steel bar according to claim 1, wherein polishing is performed by a centerless grinder after straightening.