RU2126740C1 - Method of making abrasive tool on vulcanite binder - Google Patents

Abstract

FIELD: mechanical engineering; grinding polishing and cutting wheels. SUBSTANCE: method comes to preparation of abrasive mass and rolling of semifinished articles and sheet blanks with side upsetting of edges by flexible members. Flexible members are upset by rolls with relative minimum upsetting ε_min= 50-60% which increases when moving away from rolling axis according to linear law ε = (1 + k)ε_min where k is 0.15-0.25. Rolling is carried out at friction coefficient equal to 0.40-0.45 when rolls are in engagement with flexible members. EFFECT: improved quality of abrasive wheels owing to elimination of displacement of flexible members in rolling, reduced consumption of abrasive mass. 4 dwg

Description

 The invention relates to the production of an abrasive tool on a volcanic bond, in particular grinding, polishing and cutting wheels, and can be used in the abrasive industry.

 A known method of manufacturing an abrasive tool on a volcanic bond, including the preparation of abrasive mass, rolling (rolling and calendering) sheet blanks from it, cutting out of them annular blanks of abrasive wheels, thermal (vulcanization) and machining of ring blanks to obtain an abrasive tool [1].

 The disadvantage of this method is the free transverse flow of material during rolling (rolling) from the abrasive mass of semi-finished sheet blanks and rolling (calendering) from semi-finished sheet blanks.

 With free transverse flow during rolling in two smooth rolls of an unplastic abrasive mixture containing up to 70% brittle grinding material, defects in the form of tears and cracks form on the block edges of the semi-finished products and sheet blanks. For this reason, the width of sheet blanks exceeds by 30 - 40% the diameter of the annular blanks of abrasive wheels cut from them. After cutting the circular blanks of the circles from the sheet blanks, the waste in the form of an external layer reaches 50% of the surface of the sheet blanks.

 In addition, with a free transverse flow of material during the rolling process, the specific normal and tangential forces will be distributed unevenly along the width of the deformation zone. The components of these efforts in the rolling direction will have maximum values along the longitudinal axis of symmetry of the semi-finished product and the sheet stock (X axis) and minimum values along the edges of the semi-finished product and the sheet blank. Such an uneven distribution of longitudinal forces leads to uneven roll wear on the barrel length. As a result, semi-finished products and sheet blanks after rolling will receive different heights in width, which leads to the marriage of abrasive wheels in different heights.

 The closest in technical essence and the achieved effect to the proposed is a method of manufacturing an abrasive tool on a volcanic bond, including the preparation of abrasive mass, rolling semi-finished products from it with limiting the transverse mass flow (with side compression), rolling semi-finished sheet blanks, cutting ring blanks from them , thermal and mechanical processing of workpieces to obtain an abrasive tool [2].

 With this method, in the process of rolling the mass and the gap between the rollers simultaneously with the abrasive mass, elastic elements with a height exceeding the gap between the rollers are installed, set apart from each other at a distance that provides a given width of the semi-finished product.

 This method partially eliminates the disadvantages of the rolling process from the abrasive mass of semi-finished sheet blanks with a free transverse flow of material. The number of defects in the form of gaps and cracks on the lateral edges of the semi-finished products and sheet blanks obtained from them is reduced. Therefore, the width of the sheet blanks can be reduced. In this case, waste in the form of external lining is reduced after cutting annular blanks from sheet blanks. The uneven distribution of the longitudinal normal and tangential forces along the length of the roll barrels and the uneven wear of the rolls along the length of the barrels are also reduced. As a result, the height difference in width of the semi-finished products and sheet blanks is reduced, and due to this, the marriage of circles in height difference is reduced.

 However, reducing waste in the form of an external flake after felling is not enough, reducing the marriage of circles at different heights is small, the unevenness of height allowed by normative and technical documentation, for example, cutting wheels, is too high. So, for a cutting wheel with dimensions of 200 x 2 x 32 mm, the permissible unevenness of height is 0.4 mm or 20% of the nominal height of the wheel. When cutting metals in circles with such a high unevenness of the height of the circle, excessive heating of the circle occurs, burns of the surfaces of the metal being cut, or even jamming and rupture of the circle.

In addition, this method is mainly suitable for rolling semi-finished products from abrasive masses, when the longitudinal specific normal pressure (P _x ) in the deformation zone is small and the transverse specific pressure of the rolled mass on the elastic elements (P _y ) does not exceed 0.1 P _x . If the transverse specific pressures of the rolled mass on the elastic elements exceed 0.1 P _x , then the transverse components of the specific tangential forces τ _eu (friction forces on the contact surfaces of the elastic elements with the rolls) will not be enough to hold the elements between the rolls. In this case, the elastic elements will no longer compress the abrasive mass and the side edges of the sheet stock rolled from the semi-finished product.

The semi-finished product rolled at the indicated values of P _y <0.1P _x has insufficient density and cannot be used to obtain a circle. To obtain a density> 2.6 g / cm ^{3, the} semi-finished product must be further rolled. With further rolling, the density and deformation resistance of the processed material increases. Therefore, the specific normal pressure P _x increases and, as experimental studies have shown, the specific transverse pressures of the rolled semi-finished product on the elastic elements increase to P _y = (0.3 - 0.4) P _x . In this case, the forces τ _eu will not be enough to hold the elastic elements between the rolls and the side edges of the rolling will not be crimped. To implement the rolling process with lateral compression of the abrasive mass and semi-finished products, it is necessary to increase the specific forces τ _eu that hold the elastic elements in the rolls several times. This specific force according to the law of Coulomb is equal to
τ _eu = P _e • f _e ,
where P _e - specific normal pressure on the contact surfaces of the elastic element with the rolls;
f _e - coefficient of friction on the contact surfaces of the elastic element with the rolls.

Therefore, to increase τ _eu, it is necessary to increase P _e and f _e . The value of P _e depends primarily on the compression of the elastic element by rolls. In the closest method [2], the elastic element is crimped from a height h ₀ = 4 mm to a height h ₁ = 3 mm, i.e. with an absolute compression (Δh = h ₀ -h ₁ ) 1 mm and a relative compression Δh / h ₀ = 25%. With such a small compression and a small value of f _e (at the contact of the elastic element with polished rolls f _e = 0.1), the values of P _e and τ _eu will be small.
Thus, the main disadvantage of the closest method is the displacement of the elastic elements in the processes of rolling abrasive mass or semi-finished products.

 The objective of the proposed invention is to eliminate this drawback, namely the elimination of the displacement of the elastic elements at the time of rolling, and therefore, reducing the consumption of abrasive mass and improving the quality of sheet blanks (reducing different heights and improving the accuracy of height dimensions).

The problem is achieved in that in the method of manufacturing an abrasive tool on a volcanic bond, including the preparation of abrasive mass and rolling from it semi-finished products and sheet blanks with side compression of the edges with elastic elements, according to the invention, the elastic elements are crimped with rolls with a relative minimum compression ε _min = 50 - 60%, which increases with distance from the axis of rolling according to the linear law ε = (I + K) ε _min , where K = 0.15 - 0.25, and rolling is carried out at a friction coefficient upon contact of the rolls with elastic elements equal to nom 0.40 - 0.45.

With an increase in the minimum relative compression of 2.0 - 2.4 times compared with the above method, the specific normal pressure P _e and τ _{eu will} increase 2.5 - 0.3 times, thereby reducing the risk of displacement of the elastic elements. If ε _min <50%, then P _e and τ _{eu do} not increase sufficiently, if ε _min > 60%, then the shape of the side surfaces of the elastic elements is distorted and their rapid destruction during rolling is possible.

An increase in the values of f _e in 4.0 - 4.5 times will lead to an increase in the force τ _eu and increase the reliability of the retention of elastic elements. The friction coefficient can be increased by roughening (for example, by applying marks) the contact surfaces of the rolls with the elastic elements.

The values of f _e <0.40 do not provide reliable retention of the elastic elements from displacement, and the values of f _e > 0.45 quickly lead to the destruction of the elastic elements.

Increasing the relative minimum reduction in width of the elastic elements at a distance from the rolling axis linearly may be achieved, for example, changing the width of the contact surfaces of the roll diameter with the elastic elements that gives an additional force to τ P _{eu eu.} This force is the horizontal component P _e acting on inclined surfaces F _e and equal
P _eu = P _e • sinα.
But in this case, instead of the force τ _e on the surface F _e , the elements will be held by its horizontal projection equal to
τ _eu = τ _e • cosα = P _e • f _e cosα.
The total holding force will be equal to
P _eu + τ _eu = P _e (sinα + f _e cosα).
The radius of the rolls on the surfaces F _e changes linearly when K = tgα. At K <0.15, the angle α is small (about 8 ^° ) and the component P _eu is small, at K> 0.25, the angle α is large (more than 14 ^° ) and therefore the minimum height of the rolled sheet blanks will be limited.

The proposed method is illustrated in FIG. 1 to 4, where in FIG. 1 shows a rolling pattern with lateral compression; in FIG. 2 - the same (plan view with the designation of the rolling axis X; in Fig. 3 - the position of the elastic element at the time of rolling, in Fig. 4 - a diagram of the forces acting on the contact surface F _e .

In the figures indicated:
1 - rental;
2 - elastic elements;
3 - upper rolling roll;
4 - lower rolling roll.

минимальное

Прокатные валки 3 и 4 имеют увеличение диаметров по поверхностям F_э под углом α.
Способ осуществляется следующим образом. Изготавливаются круги 300 x 3,2 x 32 из электрокорунда нормального марки 14А, зернистостью 40.The elastic elements 2 have dimensions h ₀ and b _e before entering the deformation zone. Maximum absolute compression of the elastic element

the minimum

Rolling rolls 3 and 4 have an increase in diameters on the surfaces F _e at an angle α.
The method is as follows. Circles 300 x 3.2 x 32 are made of electrocorundum of normal grade 14A, 40 grit.

In the first pass, the semifinished product is rolled from the abrasive mass with a height of 10 mm and a width of 310 ± 1 mm, which, after rolling with knife cutting, is divided into lengths of a measured length equal to 400 mm. Together with the abrasive mass, elastic elements with a height of 20 mm and a width of 20 mm are specified in the rolls. Moreover, Δh _min = 10 mm, Δh _max = 20 mm.

 After rolling, the semi-finished product has smooth edges without defects in the form of flaws and cracks.

In the second pass, a semi-finished product with a height of 4.5 mm, a width of 310 ± 1 mm and a length of 886 mm is obtained. In rolls together with a workpiece with a height of 10 mm, elastic elements are set with a height of 9 mm and a width of 9 mm. Moreover, Δh _min = 4.5 mm, Δh _max = 7.2 mm.

In the third pass, a sheet billet is rolled 3.2 mm high, 310 ± 1 mm wide and 1240 mm long. Together with the semi-finished product, elastic elements are set in rolls with a height of 8 mm and a width of 8 mm. Moreover, Δh _min = 4.8 mm and Δh _max = 7.2 mm.

 Four ring blanks are cut from a high-quality sheet blank. At the same time, waste in the form of a burr compared with the closest analogue is reduced by 7.6% and compared with existing technology by 22.1%.

 Marriage at different heights compared to existing technology decreased by 2.7%.

 It is advisable to use the method on flow-mechanized lines for rolling sheet blanks for cutting, polishing and grinding wheels on a volcanic bond.

Sources of information
1. Technological instructions for the manufacture of volcanic and flexible polishing wheels. - Chelyabinsk: South Ural Central Scientific Research Institute, 1970. - S. 32-89.

 2. Boyarshinova R.I., Pogoretskaya R.I. A.S. N 996179 B 24 D 17/00 "A method of manufacturing an abrasive tool on a limited bond." Publ. in B.I. N 6, 1983.

Claims (1)

A method of manufacturing an abrasive tool on a volcanic bond, including the preparation of abrasive mass and rolling from it semi-finished products and sheet blanks with side compression of the edges by elastic elements, characterized in that the elastic elements are crimped by rolls with a relative minimum compression ε _min = 50-60%, which increases with the distance from the rolling axis according to the linear law ε = (1 + k) ε _min , where k = 0.15 - 0.25, and rolling is carried out at a friction coefficient when the rolls contact with elastic elements equal to 0.40 - 0.45.

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