JPH0377708A - On line processing method for roll surface of cross helical rolling mill - Google Patents

Abstract

PURPOSE:To properly hold a roll gripping force by executing a knurling so as to make the roll surface in the depth shown by an expression while under the size changing of a rolled stock in the state of roll being assembled to a housing. CONSTITUTION:A roll facing device 6 is fitted to the upper part of a cross helical rolling mill. An air cylinder 11 is moved up and down by air pressure, a jig 13 is operated and punching is executed on the roll 1. The cylinder 11 is movable by the rotation of a screw 8 and can be moved to the specific position of the roll 1. The depth (h) in punching is worked in the depth as shown by an expression and the depth is adjusted by a feeding air pressure. In the expression NB: number of billet rollings, DB: billet diameter, a, b: coefficient found experimentally. Since the knurling in an optimum depth is executed on the roll 1 on each size changing, the gripping force can be held properly at all times and the productivity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for online processing of the roll surface of an inclined rolling mill for rolling seamless steel pipes using the Mannesmann method.

<Prior art> Conventionally, when rolling a seam M#j J pipe by Mannesmann method such as Mannesmann plug mill method or mandrel mill method, the raw material round billet is usually rolled by a pair of inclined rolls, a pair of guide shoes, Further, the holes are perforated by an inclined rolling mill called a piercer, which is composed of one perforation plug.

On the surface of the roll used in this tIJI inclined rolling mill,
In order to ensure the roll grip force to prevent slipping during drilling of round billets and poor biting and poor ash removal, knurling is generally applied in advance at the time of roll manufacture (for example, 3rd Edition Steel Handbook 111(2)
(See p. 935).

As shown in FIGS. 4(a) and 4(b), this knurling is applied to the gorge G by a predetermined width l2 on the entrance side 2, or between a width 1t on the entrance side 2 and a width l on the exit side 3. , a knurling 4 having a predetermined diameter d (m) and a predetermined depth h (m) is manually punched using a predetermined In gap chisel or round punch.

The deeper the depth h of this knurling 4, the greater the roll grip force and the greater the slip prevention effect. However, if it is too deep, it is likely to cause print flaws, so care must be taken, for example, 0.25 to 0.45 m. Punches are made to the same depth on the entire surface.

<Problems to be Solved by the Invention> However, in the roll surface processing by knurling as described above, as the number of rolling rolls increases and the wear of the roll surface progresses, the depth h naturally becomes shallower and F ! ! There is a problem in that the coefficient of friction decreases and the roll grip force decreases.

FIG. 5 shows an example of a situation in which the coefficient of friction between the roll surface and the rolled material varies depending on the number of rolled materials.

In the figure, the lIh line A shows the change in the PJFJ coefficient due to the knurling process on the roll surface, and as the number of rolls increases, the friction coefficient tends to decrease, while the r
The line B shows the change in the friction coefficient due to roughness on the roll surface, and it can be seen that the friction coefficient increases as the number of rolled rolls increases. Therefore, the total P7 between the roll surface and the rolled material! The friction coefficient changes in a substantially U-shape as shown by curve C, and cannot maintain a constant value.

Therefore, in order to always maintain the total friction coefficient above a predetermined value, it is necessary to knurling the roll surface when the friction coefficient drops below a certain value, but each time the roll is removed from the housing and knurling is performed manually. This is a problem because it takes time and reduces productivity.

In particular, when rolling difficult-to-work materials such as high alloy steel, a large roll grip force is required.
The rolling opportunities will be regulated.

The present invention is as described above! ! The purpose of the present invention is to provide an online processing method for the surface of an inclined rolling mill roll that solves Ia.

<! ! Means for Solving IN〉 According to the present invention, when the surface of a roll used in an inclined rolling mill for rolling seamless steel pipes is incorporated into a housing, the following formula % is applied during size change of a rolled material. Formula % Here, N: Number of round billets rolled.

D,; Round billet diameter (-1).

a, b: The above objective is achieved by processing the material to a depth h (m) determined by a coefficient determined empirically.

<Function> As a result of intensive studies to maintain the roll grip force at a predetermined value, the present inventor found that the friction coefficient (+th II A in Figure 5 above) due to the knurling process on the roll surface.
The knurling depth required to keep the value within a predetermined range during rolling is expressed mathematically, and a means is provided to punch the roll surface in a short time online to ensure that knurling depth. This is what I did.

In other words, for example, when we investigated the depth of knurling for a piercer roll used for mandrel rolls each time the size of the rolled material was changed and the rolls of the mill were changed, we found that the depth h (knurling) was the same as that of the round billet being pierced and rolled. Diameter Da (m
φ) and its rolling number N and (rolls), and the relationship between them can be expressed by the following equation (1).

h = (a-b −N*) −DI−−・−(
11 Here, a and b are dimensionless coefficients determined empirically; for example, a is 2X10-' to 5X10-'', and b is lX10- to 5X10-'.

Therefore, at the next rolling opportunity, the diameter was reduced and the ■φ round billet was rolled. The depth h of the knurling required for the main rolling is calculated in advance using the above formula (1), and the depth h
This can be ensured by punching the rolled material using the time available for resizing it before the next rolling opportunity.

Figure 3 shows the nominal friction coefficient, or roll grip force, during rolling when a knurling of the necessary depth h determined using the above (+) formula is formed on the roll surface each time the size of the rolled material is changed. This shows the progress.

As can be seen from this figure, the friction coefficient due to roll surface treatment (toward line III in Figure 5), which conventionally decreased as the number of rolled rolls increased, decreased with each knurling process as shown by curve A'. Because it can be restored and increased,
The total friction coefficient including the friction coefficient due to surface roughness of Ib line B (curve C'
It is possible to always maintain the coefficient of friction (denoted by ) higher than the minimum required coefficient of friction.

In this way, each time the size of the rolled material is changed,
By processing the surface of the roll while the J1 skew rolling mill is stopped, it is possible to always maintain the roll grip force within an appropriate range.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a front view showing an embodiment of the present invention, and FIG. 2 is a side view schematically showing a roll surface processing apparatus.

As shown in the figure, a roll surface processing device 6 is installed above each roll 1 of an inclined rolling mill consisting of a pair of rolls 1 and a pair of guide shoes 5.

As shown in detail in FIG. 2, this roll surface processing device 6 includes a pair of bearings 7, a screw shaft 8 supported by the bearings 7, and a motor 9 coupled to the screw shaft 8 so as to be freely rotatable. , a pedestal 10 screwed onto the screw shaft 8 and movable in the axial direction, that is, the length direction of the roll 1; a cylinder 11 fixed to the pedestal 10; It is comprised of a knurling jig I3, such as a round punch, which is attached.

Then, from the air pressure control device 14 via the pipe 15 (Jj
By driving the cylinder it up and down by the supplied air pressure, the jig 13 operates and punches the roll l at a predetermined position to a predetermined depth.

In addition, by making it possible to adjust the air pressure of the air pressure control device f14 in several stages, the depth h at which the roll l is punched can be adjusted to 11 sections.

Using the roll surface processing equipment R4 configured in this way,
The roll grip force can be maintained within an appropriate range by punching the knurling depth h required for the next rolling chance, which is determined by equation (1) above, each time the size of the rolled material is changed. can.

<Effects of the Invention> As explained above, according to the present invention, the roll can be knurled to an appropriate depth each time the roll is changed in size, so the roll grip force can always be maintained within an appropriate range. , it becomes possible to expand the chances of rolling difficult-to-process materials, which have been considered difficult in the past, and thus greatly contributes to improving productivity.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a side view schematically showing a roll surface processing apparatus, FIG. 3 is a detailed explanatory diagram of the present invention, and FIG. a), crest) is a side view of the roll of the inclined rolling mill, and FIG. 5 is an explanatory diagram showing the transition of the friction coefficient. Surface processing device, 8... Screw shaft, 11.
...Cylinder, 13...Knurling jig, 14.
...Pneumatic control device.

Claims (1)

[Claims] When the surface of a roll used in an inclined rolling mill for rolling seamless steel pipes is assembled into a housing, the depth h (mm) determined by the following formula is An online processing method for the surface of an inclined rolling mill roll. h=(a-b・N_R)・D_W Here, N_R: Number of rolled billets, D_W: Billet diameter (mmφ), a, b: Coefficients determined empirically.