RU2715929C1 - Control method of milling of rolled products - Google Patents

Abstract

FIELD: machine building; metallurgy.SUBSTANCE: invention relates to the field of metallurgy and machine building and can be used at milling of flat-rolled products with cylindrical cutters. Method involves optimization of treatment modes consisting in gradual increase of the number of teeth duplicating the work of each tooth forming tooth and located behind it in circumferential direction of the cutter.EFFECT: ensuring quality stabilization of milled surface of rolled metal, higher durability of cutters.1 cl, 6 dwg, 2 tbl, 1 ex

Description

The invention relates to the field of engineering and metallurgy, in particular, to the milling of continuous flat surfaces of sheet metal by cylindrical mills.

A known method of milling flat surfaces with cylindrical mills [Handbook technologist-machine builder: 2 tons / ed. AM Dalsky, A.G. Kosilova, R.K. Meshcheryakova, A.G. Suslov. - 5th ed., Revised. and add. - M.: Mechanical Engineering, 2001]. In this case, as a rule, the rectilinear movement of the workpiece intended for milling with respect to the rotating mill is carried out due to the reciprocating stroke of the working table of the milling machine. But in this way it is impossible to process a strip of conditionally infinite length due to the limited travel of the desktop. In addition, a characteristic relief, consisting of alternating scallops and depressions, a kind of ordered roughness, appears due to the discontinuity of the cutting process, on the milled surface. The height of the combs relative to the depressions h, which determines the roughness R _{Z of the} milled surface, is found from purely geometric representations as a function of the mill diameter D and the distance between adjacent combs L:

As follows from (1), with increasing L, the height of the combs increases parabolic. So, for example, for the cutter diameter D = 250 mm with an increase in L from 3 mm to 15 mm, the height of the combs should increase from h = 9 μm to h = 225 μm, which corresponds to the transition from the sixth to the first class of surface cleanliness. In turn, the classical theory of cutting, based on the notion that each of the teeth located around the circumference of the cutter leaves a separate cavity on the machined surface, determines the distance between the combs by the tooth feed formula S _Z [Toolmaker's Handbook. - L .: Engineering, 1987. - 846 p.]:

where S _M - the speed of the strip, minute feed, m / min;

n is the speed of rotation of the cutter, rpm

Z is the number of teeth around the circumference of the cutter;

S _O - feed per revolution, mm / rev.

The range of modes B, in which the formula (2) is performed, is shown in figure 1.

A known method of milling strips obtained by hot rolling [A.S. 460127 USSR, M. Cl. B23c 3/14, B21b 45/00. Device for milling hot rolled steel in a stream / V.A. Satsky, V.N. Ershov, L.S. Korneev [et al.]. - No. 1774391 / 25-8; declared 04/15/72; publ. 02/15/75, Bull. No. 6. - 3 p.: Ill.] Or continuously cast strips [Dukmasov, V.G. Efficiency of modern technologies in metallurgy / V.G. Dukmasov, V.G. Ilyichev: under the editorship of G.P. Vyatkina. - Chelyabinsk: Publishing house of SUSU, 2006. - 178 p.]. It allows you to eliminate surface defects in the workpiece foundry origin or arising during hot rolling. Here, instead of the movement of the working table of the milling machine, the movement of the strips is used, in particular, by rewinding them from the unwinder to the coiler, and, as a rule, a support roller is installed on the side of the strip opposite from the mill. The method allows to process strips of infinite length or length limited only by the maximum allowable size of a rolled roll of them. In this case, the relief of the milled rolled surface, consisting of alternating scallops and depressions, is preserved. As a rule, milled strips are intended for subsequent cold rolling. In this case, a high surface roughness can cause a characteristic type, especially for soft non-ferrous rolled products, of “scraping” or “scoring” (GOST 21014-88), caused, in particular, by inter-turn friction when unwinding the roll during rolling. Thus, a relatively slight roughness is a prerequisite for obtaining high-quality finished products, which is not always achieved by the considered method. However, as was established in the works [Nadezhkin, M.P. The formation of the surface topography during the milling of rolled strips / M.P. Nadezhkin, M.Z. Pevzner // Production of rental. - 2000. - No. 4. - S. 32-36; Pevzner, M.Z. About the milling modes and the surface topography of the milled strips / M.Z. Pevzner // Production of rental. - 2008. - No. 9. - S. 24-26], in a fairly wide range of modes of milling of rolled products of 5-10 mm / rev, the distance between the combs L was not equal to the feed S _Z (2) per tooth, and Z times more than the feed per revolution S _O (3 ):

The range of modes A, in which the formula (3) is performed, is shown in figure 1.

This is explained by the features of the milling modes used in this case, and most importantly, by the fact that milling of rolled products is fundamentally different from milling of a part rigidly fixed in the fixture - it is characterized by a softer machine-tool-fixture-tool-component system (AIDS system) [Nadezhkin, M.P. . The formation of the surface topography during the milling of rolled strips / M.P. Nadezhkin, M.Z. Pevzner // Production of rental. - 2000. - No. 4. - S. 32-36]. Indeed, the place of fastening of the strip and the place of its processing in this case can share a multimeter distance. As a result, the total accumulated elastic deformations of the strip processing site relative to the place of its fastening reach a significant value close to L. When the accumulated elastic stress forces exceed the shear resistance (rotation) forces of the cutter provided by the cutter in conjunction with the support roller, this shift occurs L value, equal in this case to feed per revolution. In this case, of all the teeth located around the circumference of the cutter, only one tooth is fully loaded, working immediately after such a displacement, which actually forms a cavity. All other teeth only smooth the resulting relief, eliminating possible burrs and other defects, due to which there is uneven wear of the cutter teeth and its quick failure. In addition, due to the fact that the length of the scallops increases Z times, respectively (1) their height increases many times (Z ² times), which may be the cause of the formation of “nadirs” during rolling.

On the other hand, at sufficiently high feed rates per revolution S _O ≥S _M / n mm / rev, L = S _Z is observed [Pevzner, M.Z. About the milling modes and the surface topography of the milled strips / M.Z. Pevzner // Production of rental. - 2008. - No. 9. - S. 24-26]. But in this case, when each of the teeth located around the circumference of the cutter leaves a separate cavity on the treated surface, the smallest defect of the cutting surface of the cutter tooth is printed on the surface of the product, impairing its quality. This defect may be the “chipping” of the tooth, the natural gap between the carbide inserts of the combined cutter, etc. Naturally, during the operation of this kind of defects, the teeth of the cutter and, accordingly, the machined surface quickly increase. Thus, in sufficiently large intervals of the milling regimes S _M / n, the dependence of the distance between the combs L on S _M / n is two horizontal lines L = S _Z and L = S _O connected by a certain intermediate line [Nadezhkin, MP The formation of the surface topography during the milling of rolled strips / M.P. Nadezhkin, M.Z. Pevzner // Production of rental. - 2000. - No. 4. - S. 32-36; Pevzner, M.Z. About the milling modes and the surface topography of the milled strips / M.Z. Pevzner // Production of rental. - 2008. - No. 9. - S. 24-26]. In figure 1, it is conventionally presented in the form of an inclined dotted line. Obviously, it was in the interval of the milling modes corresponding to this segment that one should look for those that allow you to combine the advantages of each of the modes represented by horizontal sections of the L (S _M / n) diagram, see figure 1, but avoid their inherent disadvantages.

The closest in technical essence to the proposed method is a method of controlling milling of rolled products [Pat. No. 2687638 Russian Federation, IPC В23С 3/13. The way to control milling hire [Text] / Pevzner MZ .; Applicant and patent holder of FSBEI HE “Vyatka State University”. - No. 2018127480; declared 07/25/2018; publ. 05/15/2019, Bull. No. 14], based on the works of [Nadezhkin, M.P. The formation of the surface topography during the milling of rolled strips / M.P. Nadezhkin, M.Z. Pevzner // Production of rental. - 2000. - No. 4. - S. 32-36; Pevzner, M.Z. About the milling modes and the surface topography of the milled strips / M.Z. Pevzner // Production of rental. - 2008. - No. 9. - S. 24-26] and equation (3). To increase the resistance of the cutters on one side and to prevent the transfer of defects of the cutters on the machined surface on the other, the treatment mode (S _M / n) is assigned according to a pre-established regression dependence of its relationship with the distance between the scallops L so that the distance between the scallops is any value in the interval L '= (2 ÷ 4) × S _Z. That is, for a particular process, the true shape and position of the line connecting L = S _O and L = S _Z is determined, and then the conditionally “intermediate” processing mode (S _M / n) is assigned (milling mode B, see figure 1), when which sets a certain number of teeth (1 ÷ 3), duplicating the work of each tooth forming a cavity.

But the number of duplicate teeth necessary to obtain a milled surface of satisfactory quality, depending on the condition of the cutter, can vary from one (n = 2, a high-quality cutter perfectly assembled and / or sharpened) to 3-4 or more (worn-out cutter, teeth which abound in chips and other defects). Such a large number of duplicate teeth is designed to guarantee the compensation of “imprinted” on the milled surface traces of defects in the teeth of the milling cutter to satisfy even the increased requirements for the quality of the milled surface. Of course, if this kind of guarantee cannot be provided, the mill needs to be replaced. That is, the higher the requirements for the quality of the milled surface and the more damage to the mill, the more duplicate teeth should provide the selected processing mode. Thus, it is not enough to avoid both extremes: L = S _Z and L = S _O (work with each tooth in a separate cavity and with all the teeth on the circumference of the cutter in one cavity) - it is necessary to correlate the number of duplicate teeth with a number of circumstances. The ultimate "beneficiaries" of the right choice of processing mode should be the achievement of a consistently high quality and increased tool life.

The aim of the proposed invention is to increase the efficiency of the milling process and the quality of the final product.

The technical result of the proposed invention is to stabilize the quality of the milled surface throughout the life of the cutter, thereby increasing the yield during the production of rolled products, to increase the productivity of the process, as well as to extend the life of the cutter to the maximum possible limit.

This result is achieved by assigning a processing mode (the ratio of the strip speed and the rotation of the cutter) according to a pre-established regression dependence of its relationship with the distance between the scallops L 'so that the condition

where S _Z is the calculated value of the feed per tooth.

n = 2 is the number of teeth processing one cavity (one duplicate tooth).

During operation of the cutter, at the slightest sign of deterioration in the quality of the machined surface, the processing technology is adjusted (parameter S _M / n is reduced), thereby increasing the number of teeth duplicating the work of each tooth forming the cavity and the distance between the combs L '. The process is stopped and the mill is sent to the next sharpening when the distance between the combs reaches the critical value _CRIT for the given process. (Size L _CRETE defined previously customer requirements or, if a subsequent cold rolling, the conditions of its implementation, for example, relatively soft materials are more prone to the formation Nadirov require minimal value L _CRIT). Thus, it performed "corner" milling control condition in in accordance with the proposed method, when the number of teeth duplicating the work of each tooth forming a cavity depends on the condition of the cutter, the degree of its wear and gradually increases in the process of operation. The more defects (chips, “chipping”, etc.) are present on the teeth of the cutter, the greater the number of teeth duplicating the work of each tooth forming a cavity is required to compensate for these defects and guarantee a high-quality surface of the finished product. The condition L <L _CRIT provides a relatively small distance between the scallops and a relatively small roughness, and by increasing the number of duplicate teeth, it is ensured:

- stabilization of the surface quality of the milled rolled products and the finished product, regardless of the degree of "wear" of the tool;

- increase durability (time period and the amount of material processed between the operations of sharpening mills) and, consequently, the total service life and efficiency of use;

- reducing the operating time of the mill to its next replacement for sharpening, and, consequently, the total time spent on replacing the milling cutter, and, as a result - increasing the productivity of the milling line.

Description of the method.

The proposed method includes:

- continuous milling of rolling, consisting in the movement (rewind) of the strip relative to the rotating cutter;

- preliminary determination of the relationship of the milling mode (the ratio of the speeds of the strip and the rotation of the cutter) with the profile of the milled surface (the distance between the scallops L);

- determination of the milling mode on the basis of its relationship with the distance between the combs and from the condition L = 2 × S _Z , where S _Z is the calculated value of the feed per tooth (4) and the execution of the technological operation in the selected mode;

- when there are signs of deterioration in the quality of the milled surface, adjusting the milling mode in the direction of decreasing the parameter S _M / n and performing the technological operation in the mode optimal for the current state of the milling cutter;

- mode control process of milling and processing continues under preservation conditions L <L _CRETE and stops at the L≥L _CRIT.

Execution example.

The processing was carried out in a double-sided milling line, consisting, in particular, of a straight-unwinding machine, scissors, “on-line” milling machines [Handbook of a machine-building engineer: 2 tons / ed. A.M. Dalsky, A.G. Kosilova, R.K. Meshcheryakova, A.G. Suslova: 5th ed., Revised. and add. - M.: Engineering, 2001] the upper and lower sides of the strip and convolutional machine. The distance between the pulling rollers with the subsequent leveling machine, relatively rigidly connected with the machined strip, and milling machines was 8 ÷ 12 m. The technological characteristics of the line are presented in table 1, and a general view is shown in figure 2.

As a tool used prefabricated cylindrical mills with a diameter of ~ 250 mm with 14 helical teeth (ω = 25 ° 53 'degrees) [Bannikov, E.A. Milling machine manual / E.A. Bannikov. - Rostov n / A: Phoenix, 2005. - 320 p.] (Figure 3). They were “recruited” from P6M5 alloy plates, and then sharpened at the rear α = 12 ° and the front γ = 3 ° angles. To control the sharpening angles, we used the 2URI goniometer according to TU2-034-617-84.

The thickness of the film was ~ 0.3 mm. Hot-rolled strips of brass L63 were processed with a thickness of ~ 8 mm and a width of ~ 650 mm, varying n, S _M. The actual distance L and the transformation of the cavity between the “scallops”, the resistance of the cutters and other technological parameters were controlled, and the feed per tooth S _Z (2), feed per revolution S _O (3) and the ratio L / S _Z , which determines the number of teeth, were calculated sequentially processing one cavity, table 2. Control of the distance between the combs was carried out by measuring with a measuring ruler the length of 10 cavities.

It can be seen that when milling according to the traditionally used modes No. 1 and No. 2 (see table 2, figure 1), the distance between the scallops (L≈10 mm) was equal to not applying to the tooth S _Z , and Z times as much - applying to the revolution S _O. That is, it was not formula (2) that was executed here, but formula (3) and the strip surface was rather rough, Figure 4. As a result of subsequent cold rolling on a three-stand mill to a size of 1.8 ÷ 2.0 mm, nadirs were found on the surface of the tape.

In order to reduce L and, thus, prevent the formation of nadirs, we used a regime based on a decrease in the feed rate S _M and a corresponding decrease in the feed per revolution S _O = S _M / n (traditionally used regime No. 3, see table 2). Using this mode increased the cleanliness of the milled surface and eliminated the formation of nadirs during subsequent rolling, but at the same time L = S _{O was} preserved, as well as uneven load on the teeth and low resistance of the cutters. In addition, a decrease in the ratio S _M / n due to a decrease in the feed rate S _M is associated with a corresponding decrease in the productivity of the milling line. When S _M / n changed upward, the initially established ratio L = S _{O was} maintained and the distance between the combs increased (L = S _O ≈13.3 mm / rev, mode No. 4, see table 2, figure 1).

A further decrease in n to n = 200 rpm, which ensured the ratio S _M / n = 40 mm / rev (mode No. 5, see table 2), led at first glance to a paradoxical phenomenon: instead, L = S _M / n = S _O (3), the relation L'≈S _Z = S _M / (n × Z) (2) was fulfilled, see figure 1. (The depression between the ridges of length L splits into 14 shallow depressions with the distance between the ridges of length L '= S _Z. ) Since mainly these small depressions of length L 'determined the roughness of the profile of the milled strip, it became much more even (1). However, it should be noted that the large initial depressions did not disappear at all, but remained in the form of waves that were slightly noticeable in height, each of which is still equal in length to L = S _O = S _M / n. (Table 2 in one column presents the values of L in the case when the cavity between the combs is in a “whole state”, and L '- after its decay, the distance between the combs of the small cavities)

Thus, the phenomena of sequential operation in one place of the strip of all teeth located around the circumference of the cutter can be avoided by increasing the ratio S _M / n. (With a further decrease in n and, consequently, an increase in S _O = S _M / n> 40 mm / rev, the ratio L '= S _{Z was} maintained.) The fulfillment of the ratio L' = S _Z led to the need to comply with special requirements for the quality of mills, but even in this case, on the surface of the strips treated with newly sharpened mills, traces of structural gaps between carbide inserts were observed. In the process, the “chipping” of each cutter tooth led to the appearance of a significant defect on the treated surface and, as a consequence, to the need for frequent replacement of cutters and the ineffectiveness of their use. Indeed, in this case, each tooth processes a separate cavity, and duplication of its work by the next tooth along the circumference of the cutter is not carried out, as a result of which the milled profile began to accurately reflect the defects of the processing tool.

In order to eliminate both adverse extremes - nadir during subsequent rolling (modes 1, 2) and the need for frequent replacement of cutters (mode 5), an intermediate mode was used, corresponding to the dashed line connecting the horizontal sections of the graph schematically shown in Figure 1. In our case, for the double-sided milling line used, the extreme values of this transition line of the communication function L (S _M / n) are already known: the interval of the change of L from L = S _O to L '= S _Z corresponds to the interval of the processing modes 13 mm / rev <S _M / n <40 mm / rev (It can be seen that with a minute feed of S _M = 8 m / min, such modes are achieved by varying the cutter rotation speed in the range of 200 rpm <S _M / n <600 rpm, see table 2.) This intermediate mode 6 (S _M / n≈26.7), see table 2 (prototype), just as mode 5 provided a “splitting” of the large initial depression (L≈26.7 mm) into intermediate depressions with a distance between combs L'≈4.5 mm (see table 2). But, unlike all the previous modes, the distance between the combs L 'occupied an intermediate position between the values of S _Z and S _O corresponding to this mode (~ 1.9 mm / tooth <~ 4.5 mm <~ 26.7 mm / about). In this case, there was a general alignment of the profile (figure 5) in comparison with the traditionally obtained (compare with figure 4).

To establish the initial processing mode, which ensures, in accordance with the proposed method, duplication of the work of the tooth forming the cavity with another tooth, it is necessary to establish the location and shape of the dashed line of the transition from L = S _O to L '= S _Z (see figure 1) as a preliminary the distance between the scallops L 'from the milling mode (S _M / n). (In each case, it depends primarily on the layout and total rigidity of the equipment used, the number of teeth around the circumference of the cutter, but also, albeit to a lesser extent, on frequently changing factors: the mechanical properties of the material being processed and the degree of eccentricity of the cutter installation.) mode 6 (S _M / n≈26,7 mm / r) value of the distance between the crests of small depressions L 'accurately determine the true shape of the intermediate transition portion, figure 6, which determines the function _{L' = f (S M /} n) and Ini- cial represented by a straight line (see. the dotted line in Figure 1). Similarly, the dependence of the approximate number of teeth processing one small depression L '/ S _Z (see table 2), on the processing mode - L' / S _Z = f (S _M / n), see figure 6, table 2. Power functions in this case provide a significantly higher degree of approximation (determination coefficient R ² ): L (L ') = 417.1 (Sm / n) ^-1.35 mm; R ² = 0.99; L / Sz = 5963 (Sm / n) ^-2.35 ; R ² = 0.996. (The degree of approximation of the initially specified linear coupling function L (S _M / n) of the transient mode, see the dashed line in Figure 1, was only R ² = 0.82 ÷ 0.86.) To select a processing mode that provides one “duplicate” tooth, that is, the number of teeth processing one cavity L '/ S _Z ≈ 2 (the proposed method), used the graph of the dependence L' / S _Z = f (S _M / n), see figure 6. But at the same time solved the inverse problem : according to the graph from the value of L '/ S _Z = 2 (ordinate axis) on the abscissa axis, the processing mode was determined - S _M / n≈30 mm / rev.

This initial mode was carried out by setting: S _M = 6 m / min, n = 200 rpm. During the processing of the strips, upon detection of the slightest signs that can be identified as milling defects, the cutter rotation speed was increased by ~ 20 rpm each time, thereby decreasing S _M / n and increasing L '. Comparing L 'with a predetermined value for the bands L63 _CRETE L = 8 mm. Upon reaching L'≥8 mm, “transshipment” was carried out, after which the process was resumed.

To assess the effectiveness of the proposed method, the processing was performed in comparison:

- the proposed method, starting from mode 7 and increasing as necessary n until the achievement of L'≥8 mm;

- the prototype method (mode 6, which remains constant until the appearance of signs of unacceptable defects on the treated surface).

After achieving these critical features for each processing method, the cutter was sent to sharpening and replaced with another cutter of the corresponding processing method. Then, the milling was resumed until critical signs for each processing method and the replacement of the cutter with a sharpened one after initial use appeared. Such processing cycles were repeated, controlling the amount of milled material by each mill for each cycle and for the entire time that each mill was used until it was fully developed.

During the experimental work, the “nadir” defects were not found on the surface of the tape rolled from strips milled in accordance with both processing methods. Since the change in the ratio S _M / n by the proposed method was made by gradually increasing n, the change in the mode did not lead to a decrease in productivity and did not affect the operation of the second milling machine processing the other side of the strip. But at the same time, the quality of the milled surface during the machining cycle and the entire operation time of the cutter remained stable high due to regular adjustment of the mode. On the contrary, the quality of the surface milled in accordance with the prototype gradually decreased during the cycle of the milling cutter between its regrind, remaining, however, within the limits of the requirements. Regulation of the processing mode depending on the quality condition of the cutter made it possible to increase the volume of material milled in accordance with the proposed method for the entire period of operation of the cutter (i.e., cutter resistance) by ~ 25%, and for the processing cycle between sharpening (and the cycle time itself) by ~ 40%. As a result, due to the reduction in the total time spent on “transshipment”, productivity increased by ~ 5%.

Thus, the proposed method of controlling strip milling will stabilize the surface quality of the machined rolled products, increase the productivity and resistance of the mills, and, consequently, the efficiency of the milling process and the entire tape production.

Claims (1)

 A method for controlling rolling milling, including rewinding a strip of a strip relative to a rotating cutter, in which the relief of the milled surface, determined by the distance between the ridges of cavities formed by the cutter on the strip surface, is controlled by changing the processing modes, and the ratio of the strip speed and the rotation of the cutter is set according to previously established regression dependencies, depending on the number of teeth located around the circumference of the cutter, following each forming cavity in a tooth and duplicating its work, characterized in that initially the ratio of the speeds of the strip and the rotation of the cutter is determined from the condition that the work of each tooth forming the cavity is duplicated by one tooth following it, then, as the cutter works, the ratio of the speeds of the strip and the rotation of the cutter is reduced and increase the number of teeth duplicating the work of each tooth forming the cavity of the tooth, and the distance between the scallops until the specified distance exceeds a predetermined critical value.

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