JPH04100615A - Rolling caliber roll - Google Patents

Abstract

PURPOSE:To prolong the life of a roll by giving compression stress in the width direction of a roll body to the bottom part of a caliber. CONSTITUTION:A rolling caliber roll is composed of a hollow roll body 11 having a caliber 11-2 and a roll shaft 12 fitted tightly into the hollow part 11-1 of this roll body. Then, a shrink bit allowance 11-3 or a cold fit allowance is made large on both sides in the width direction of the roll body 11 and reduced gradually toward the central part. Compression stress in the width direction of the roll body is given by the shrink bit or cold fit of this roll body to the bottom part of the caliber 11-2. In this way, effect preventing cracks on the roll body can be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rolling roll used for groove rolling of tubes and bars, and more particularly to a rolling groove roll assembled from a roll body and a roll shaft.

Conventional technology A rolling groove roll used for groove rolling of pipes and bars consists of a hollow roll body (1) having grooves (1-1) and a hollow roll body (1) having grooves (1-1), as shown in Fig. 9. It consists of a roll shaft (2) that fits tightly into the hollow part.

In the case of this grooved roll for rolling, the roll body (
Due to the surface pressure P acting on the hole (1-1) in 1), a tensile stress σt acts on the bottom cross section of the hole of the roll body.

The distribution of this tensile stress σt has a maximum value on the hole bottom surface of the roll body (1), and if this maximum value is σtrnax, the surface pressure P may be high depending on the rolling conditions, resulting in σtmax
becomes high, and when this σtmax exceeds the material strength of the roll body, cracks will appear on the bottom surface of the hole and cracks will occur in the roll body.

In addition, cracks are more likely to occur on the hole-shaped bottom surface of the roll body due to repeated thermal stress caused by processing heat and cooling by lubricating oil.

As a countermeasure against roll cracking, conventional methods have been used to change the roll material to a material with higher strength, but this increases the cost of the roll and generally reduces the toughness of high-strength materials, leading to cracking due to impact. There is a problem in that it is easy to cause

Another known method is to provide a gap between the contact surface between the roll body and the roll shaft (Japanese Patent Publication No. 59-2
561, JP-A No. 61-216807)
.

In both of these methods, by forming a recess in the center of the roll body or at the corresponding roll axis position,
The roll is deflected by the vertical component of the surface pressure during rolling to generate compressive stress at the bottom of the groove, thereby reducing the tensile stress at the bottom of the groove caused by the rolling force.

In other words, the roll reaction force generates bending stress on the bottom cross section of the roll hole, and this bending stress becomes compressive stress on the roll hole surface, so this compressive stress reduces the above-mentioned maximum tensile stress σtmax and prevents cracking. This is a method of measuring

Problems to be Solved by the Invention However, even with the above-described method of forming a recess at the center of the roll body or at the corresponding roll axis position, cracks and roll breaks could not be sufficiently prevented for the following reasons. .

Figure 10 shows the vertical component of the surface pressure (roll reaction force) P applied to the groove roll of a cold pilger rolling mill in which a groove whose radius gradually decreases in the circumferential direction is formed, and the cross section of the bottom of the groove generated by this. The average tensile stress σH and the tensile stress σT on the bottom surface of the hole
(corresponding to σtmax in FIG. 9) and shows an example of the distribution value in the roll circumferential direction, where the horizontal axis is the position in the roll circumferential direction, and the vertical axis is the roll reaction force and tensile stress.

That is, according to this figure, the roll reaction force P is maximum near section N090.3 in the roll circumferential position, and the average tensile stress σH is maximum at the maximum position of the roll reaction force P. However, the tensile stress σT on the bottom surface of the hole is maximum at section No. 0.55.
It can be seen that it is nearby.

In this way, the reason why the position of maximum tensile stress on the bottom surface of the hole deviates in the direction of national control, that is, toward the side where the radius of the hole is smaller, with respect to the position of maximum roll reaction force is because the average tensile stress σH increases as the roll reaction force increases. Therefore, even if the roll reaction force is the same, as the hole radius becomes smaller, the tensile stress σT on the hole bottom surface increases due to stress concentration. The position where the stress σT is maximum shifts toward the smaller hole radius.

In addition, the crack-prone area of the grooved roll in the figure coincides with the maximum position of tensile stress σT on the grooved bottom surface.If the above-mentioned concave formation technique is adopted for the grooved roll showing such distribution, The compressive stress generated at the bottom of the roll hole mold depends on the magnitude of the roll reaction force itself, so the compressive stress generated at the position of maximum tensile stress on the bottom surface of the hole mold is greater than the compressive stress generated at the position of maximum roll reaction force. Therefore, the effect of compressive stress at the position of maximum tensile stress on the bottom surface of the hole is small, and roll cracking occurs.

In view of the above-mentioned circumstances, the present invention aims to solve the above-mentioned problems of the method of forming a recess at the center of the roll body or at the corresponding roll axis position, and to provide a grooved rolling roll with a long life and low cost. That is.

Means for Solving the Problems This invention provides that, in a state in which a hollow roll body having a groove and a roll shaft are combined, a compressive stress in the width direction of the roll body is applied to the bottom of the groove; In addition to applying this compressive stress, the gist of the roll is a grooved roll for rolling, which is provided with a concave void on either or both of the inner surface of the axially central portion of the roll body and the outer surface of the corresponding roll shaft. It is something.

In a rolling groove roll consisting of a hollow roll body with a working hole and a roll shaft, by applying compressive stress in the width direction of the roll body to the bottom of the groove, holes that can cause cracks and cracks can be eliminated. Maximum value σTl of zero tensile stress on the mold bottom surface
l1aX can be lowered.

As a means for applying the compressive stress, when assembling the roll body and the roll shaft by shrink fit or cold shrinkage, the shrink fit or cold shrinkage margin is large on both sides of the roll body in the width direction toward the center. Compressive stress can be applied to the bottom of the hole mold by gradually decreasing the pressure.

Furthermore, at this time, by providing a concave cavity on either or both of the inner surface of the axially central portion of the roll body and the corresponding outer surface of the roll shaft, the compressive stress generated on the hole surface can be reduced by shrink fitting or cold fitting. A large compressive stress can be applied to the bottom of the groove by the compressive stress generated at the bottom of the groove by greatly reducing the shrinkage allowance on both sides of the roll main body in the width direction toward the center.

That is, as a specific method for gradually decreasing the shrinkage fit or cold shrinkage allowance on both sides of the roll body in the width direction toward the center, the following method can be used.

(a) A method in which a roll shaft whose outer diameter gradually decreases in a tapered manner toward the center of the roll body is shrink-fitted or cold-shrinked into a roll body having the same inner diameter in the shrink-fit or cold-shrink portion of the roll shaft. .

(b) A method of shrink-fitting or cold-shrinking a roll shaft having the same outer diameter and a roll body having a hollow portion whose inner diameter tapers toward the center in the width direction of the roll body.

(c) A method in which a concave cavity is provided in the hollow part of a roll body with an equal inner diameter, and a tapered roll shaft whose outer diameter gradually decreases toward the center of the roll body is shrink-fitted or cold-shrinked.

(d) A method in which a concave gap is provided in a hollow portion whose inner diameter tapers toward the center in the width direction of the roll body, and a roll shaft having the same outer diameter is shrink-fitted or cold-shrinked.

Another method is to use a method in which a press ring having a circumferentially corresponding press head is screwed or keyed onto the roll shaft at the hole-shaped bottom of the roll body, and compressive force is applied using a lock nut or tightening nut. I can do it.

Embodiment FIGS. 1 to 4 illustrate the roll body and roll shaft of the grooved roll for rolling according to the present invention.
) is a longitudinal cross-sectional view showing the roll shaft, and Figure (B) is a longitudinal cross-sectional view showing the roll body with some parts omitted. It gradually decreases.

Figure 1 shows a roll body (11) having a hollow part (11-1) with the same inner diameter, and the outer diameter of the shrink-fitted or cold-shrinked part tapering gradually from both ends of the roll body toward the center. It is a grooved roll formed by combining a roll shaft (12) that
Shrink fit or cold fit allowance (11-3) is provided.

In other words, in the case of this grooved roll, when the 5 roll bodies and the roll shaft are shrink-fitted or cold-shrinked, the roll shaft (1
Compressive stress is generated at the bottom of the roll hole mold (11-2) due to the Taber action of 2).

Figure 2 shows a roll shaft (22) with the same outer diameter and a hollow part (22) whose inner diameter tapers toward the center in the width direction of the roll body.
21-1>, and a roll body (21) having a shrink fit or cold fit allowance (21-1).
-3), and in the case of this groove roll, the compressive stress generated at the bottom of the groove (21-2) due to shrink fit or cold shrinkage is substantially the same as that in Fig. 1 above. are equivalent.

Figure 3 shows a roll body (31) with a hollow part (31-1) having the same inner diameter and a concave gap (31-3) in the center in the roll direction, and the roll shaft shown in Figure 1. This is a grooved roll formed by combining the same tapered roll shaft (32).

In this case, the compressive stress caused by the shrink fit or cold fit allowance (31-4) and the compressive stress generated by the deflection of the roll due to the concave gap (31-3) are applied to the bottom of the hole mold (31-2). occurs in

FIG. 4 shows a roll body (41) in which a concave gap (41-3> is provided in the center of the roll width direction of a hollow part (41-1) whose inner diameter tapers toward the center of the roll body; This is a grooved roll formed by combining a roll shaft (42) with the same outer diameter, and in this case as well, compressive stress due to shrink fit or cold fit allowance (41-4>) and concave voids are (41
Compressive stress generated by the deflection of the roll due to -3) is generated at the bottom of the hole mold (41-2).

Here, to explain the mechanism of generating compressive stress due to shrink fit or cold shrinkage when the inner surface of the roll is machined into a tapered shape, as shown in Figures 5 and 6, the shrink fit or cold shrinkage allowance is δmin at the center in the width direction of the main body and δmax at both ends, and when shrink fitting or cold tight fitting is performed, the roll deforms in the shape of a broken line and forms a hole (21-2) (41
-2) Compressive stress is applied to the bottom.

Next, a method for determining the shrinkage fit or cold shrinkage allowance will be explained.

■ Average shrink fit or cold fit allowance (δmean) In the case of conventional pilger rolling rolls (no taper processing, no concave voids), this is to prevent slip between the roll body and the roll shaft. The shrink fit or cold shrink force is set as a design specification, and the shrink fit or cold shrink allowance is also set to ensure this shrink fit or cold shrink force.

Therefore, as shown in Figure 5, the shrink fit or cold shrinkage allowance is δmax on both sides of the roll body and δmi at the center.
In the case of n, the average shrink fit or cold fit allowance δmean
((δmax+δm1nX1/2) 'r is set to be equal to or larger than the set shrink fit or cold fit allowance.

■ Maximum shrink fit or cold fit allowance (δmax) The roll shaft and roll body are made of, for example, JIS-3KD class 11, and the strength is adjusted by final quenching and tempering.The tempering temperature varies depending on the steel type, but it is low. The average temperature is about 250°C.

In addition, in the case of shrink fitting, it is necessary to avoid the heating temperature of the roll body from exceeding the above-mentioned tempering temperature, and in order to prevent the surface of the roll body from softening, the temperature is preferably about 200°C or less. .

Therefore, the maximum shrink fit allowance δmax is based on the thermal expansion allowance due to heating of the roll body, and the maximum cold fit allowance δ
max is determined based on the shrinkage margin due to cooling of the roll shaft, and in consideration of workability and the like.

■ Once the minimum shrink fit or cold fit allowance (8m1n), average shrink fit or cold fit allowance (δmean), and maximum shrink fit or cold fit allowance (δmax) are determined, δ
min can be calculated using the following formula.

δmin = 2δmean-δmax δ as above
max and δmin are determined, and both sides of the roll body are δm
The roll shaft or the hollow part of the roll body is processed into a tapered shape so that ax and the central part thereof are δmin.

In addition, as shown in Fig. 6, in the case of a grooved roll having a concave cavity in the hollow part of the roll body, the concave cavity is used to ensure shrink fit or cold shrink fit force during shrink fit or cold shrinkage. Therefore, the average shrink fit or cold fit allowance δmean on both sides is set large depending on the width of the concave gap, and the maximum shrink fit or cold fit allowance and the minimum shrink fit or cold fit allowance are determined. do.

When the shrink fit or cold fit allowance is determined as described above, the taper degree of the shrink fit or cold fit allowance (Fig. 5a)
, FIG. 6 β), the flange portion of the roll body falls in the direction of the groove, and a compressive stress σA corresponding to the Taber angles α and β acts on the bottom of the groove.

By the way, as a result of determining the Taber angle for shrink fit or cold fit as described above, the compressive stress σ acting on the bottom of the hole is
As A increases, the tensile stress σB acting on the center of the hollow part also increases, and σT acting on the bottom surface of the hole during rolling increases.
The value obtained by subtracting the previously applied compressive stress σA from max may be smaller than the tensile stress σB acting on the center of the hollow portion.

In such a state, although roll cracking from the bottom of the hole can be prevented, roll cracking from the center of the hollow part may occur (because the tensile stress σB is large). At this time, the Taber angle of the shrink fit or cold fit allowance is made small so that the value obtained by subtracting σA from σTmax is approximately σB.

Further, in the case of a roll in which a concave void is provided in the hollow portion of the roll body, compressive stress acts on the bottom portion due to deflection of the roll due to the concave void. The sum of this compressive stress and the compressive stress caused by the Taber angle of the shrink fit or cold fit allowance is subtracted from the tensile stress σTmax acting during rolling, and the result is less than the tensile stress σB acting at the center of the hollow part. 41
You can do the same thing as when it gets colder.

Fig. 7 shows an example of a grooved roll in which compressive stress is applied to the bottom of the groove by a pressing ring. Figure (A) shows a roll with the same groove in the circumferential direction, and Figure (B) shows a roll with the same groove in the circumferential direction. Each is shown below.

That is, Figure (A>) shows a grooved roll consisting of a combination of a roll body (51) having the same circumferential groove (51-2) and a roll shaft (52) fitted inside the roll body. A male thread (52-1) is formed on the roll shaft, and a perfect circular pressing ring (53) having a pressing head portion (53-1) corresponding to the circumferential direction at the hole bottom is attached to the roll shaft together with a lock nut (54). It is screwed into a male screw (52-1) and applies compressive force to the bottom of the hole.

Figure (B) shows a grooved roll consisting of a combination of a roll body (61) having circumferentially tapered holes (61-2) and a roll shaft (62) fitted into the roll body. A non-perfect circular pressing ring (63) having a pressing head portion (63-1) corresponding to the circumferential direction at the bottom of the mold is fitted onto the roll shaft (52), and the pressing head portion (53-1) and the hole mold are fitted around the roll shaft (52). To make it compatible with the bottom, it is prevented from rotating with a sinking key (65), and for tightening, screw the Nara I- (64) into the male screw (62-1) of the roll shaft to apply compressive force to the bottom of the hole mold. This is what I did.

Note that both figures (A) and (B) show a concave cavity (513
), (61-3) can be used in combination.

Example 1 Table 2 shows the results of rolling under the conditions shown in Table 1.

Sample No. 1 is an inner flat roll, No. 2 is an example in which the present invention shown in Fig. 1 is applied to an inner flat roll,
No. 3 is a roll with grooves on the inner surface of the roll, No.
, 4 is an example in which the present invention shown in FIG. 3 is applied to a roll with grooves formed on the inner surface of the roll, and both are based on the shrink fitting method.

As is clear from the results in Table 2, in the case of the roll of the present invention, which uses a tapered roll shaft to apply compressive stress to the bottom of the roll hole, the roll life is 3 to 4 times longer than that of the conventional roll. Obtained.

In addition, in the case of rolls with grooves on the inner surface of the roll, compressive stress caused by the bending of the roll due to the concave voids on the inner surface of the roll is added to the compressive stress caused by the action of the tapered roll shaft, which is three times that of conventional rolls. The above roll life was obtained.

Furthermore, similar results were obtained using the cold fit method and the use of pressure rings.

Effects of the Invention As described above, the present invention provides a method for shrink fitting or cold shrinkage between the roll body and the roll shaft of a grooved roll having a flat hollow part or a grooved roll having grooves in the hollow part of the roll body. is largely reduced toward the center on both sides of the roll body in the width direction, and compressive stress in the width direction of the roll body is applied to the bottom of the hole by shrink fitting or cold shrinkage force, or by using a pressing ring. Therefore, the effect of preventing the roll body from cracking is extremely large, and the life of the roll can be significantly extended without using an expensive and high-strength roll material.

[Brief explanation of the drawing]

Figures 1 to 4 illustrate the grooved roll for rolling according to the present invention. Figure 1 (A) is a side view showing the tapered roll shaft, and Figure 1 (B) is a hollow portion with the same inner diameter. 2(A) is a side view showing a roll shaft having the same outer diameter, and FIG. 2(B) is a side view showing a roll body having a tapered hollow portion. A vertical sectional side view with parts omitted; FIG. 3(A) is a side view showing a tapered roll shaft;
FIG. 4(B) is a longitudinal sectional side view partially omitting a roll main body having a recessed part in a hollow part with the same inner diameter, and FIG. 4(A) is a side view showing a roll shaft with the same outer diameter. Figure (B) is a longitudinal sectional side view partially omitted showing a roll body with a concave part provided in a tapered hollow part, and Figure 5 is a roll body with a tapered hollow part and a roll shaft with the same outer diameter. An explanatory diagram showing the mechanism of generating compressive stress by shrink fitting or cold shrinkage of a grooved roll. Figure 6 shows a grooved roll consisting of a roll body having a concave portion in a tapered hollow part and a roll shaft with the same outer diameter. 7 (A) and 7 (B) are illustrations of a grooved roll for rolling using a pressing ring, and (A) is an explanatory diagram showing the generation mechanism of compressive stress due to shrink fitting or cold shrinking. 8A and 8B are schematic diagrams showing roll types in an embodiment of the present invention. FIG. 8B is a longitudinal side view showing rolls with the same hole type. , Fig. 9 is an explanatory diagram showing the distribution of the tensile stress σT acting on the grooved bottom cross section of the rolling roll due to the surface pressure P, and Fig. 10 shows the vertical component of the surface pressure applied to the same grooved roll and the pores caused by this. It is a figure which shows an example of the roll circumferential direction distribution value with the tensile stress of a mold|type. 11.21.31.41.51.61... Roll body 12.22.32.42.52.62... Roll shaft 11
-1.21-1.31-1.41-1, Hollow part 11
-2.21-2.31-2.41-2.51-2.61
-2... Roll hole type 11-3.21-3.31-4. 31-3.41-3.51-3. 53.63...Press ring 54...Lock nut 64...Tightening size nut 41-4...Shrink fit allowance 61-3...Concavity Fig. 5 Fig. 6 (A) Fig. 7 (B) f6-1

Claims (1)

[Scope of Claims] 1. A grooved roll for rolling comprising a hollow roll body having a groove and a roll shaft tightly fitted into the hollow part of the roll body, the roll having a groove at the bottom of the groove. A grooved roll for rolling, characterized in that compressive stress is applied in the width direction of the main body. 2. The rolling roll according to claim 1, wherein the rolling roll has a concave void on either or both of the inner surface of the widthwise central portion of the roll body and the corresponding outer surface of the roll shaft. Hole roll.