RU2025159C1 - Protecting-relieving device for roll mill stand - Google Patents

Abstract

FIELD: protection of roll mill stand against processing overloads. SUBSTANCE: protective-relieving device has breakable member and punch with body defining working chamber containing pressure-transmitting material. Device is positioned between pressure member and roll chuck. Breakable member is formed by side wall of body separated from base and grooved band ring. Elastomeric material, for example polyurethane, is used as pressure-transmitting material. Device may be provided with motion limiting member formed as cylinder rigidly connected with punch and mounted in axial alignment with pressure member. In case elastomeric material is used, band ring may be provided with flange disposed on inner surface of ring at the side of its supporting end. EFFECT: increased efficiency in protecting roll mill stands against overloads and enhanced reliability in operation. 7 dwg

Description

 The invention relates to rolling production and can be used to protect the working stands of rolling mills from technological overloads.

 A safety device of a rolling stand is known, including a wedge safety mechanism located between the roll cushions and the pressure device, made non-self-locking, with a spring element located between the wedge and the adjusting screw (ed. St. N 601060, class B 21 V 33/00).

 The disadvantage of the wedge mechanism is the instability of the magnitude of the response force due to the effect of running-in of the rubbing surfaces, as well as getting into the working contacts of the mechanism of particles of scale, water, grease, vapor, etc., which changes the coefficient of friction.

 A rolling stand safety device is also known, located between the pressure mechanism and the roll roll cushion, in which packets of flexible plates installed with their plane parallel to the perceived load are used to limit technological loads (ed. St. N 1011288, class B 21 V 33/00) .

 The known device reduces the rigidity of the rolling stand due to the deflection of the plates before losing their stability, and is also subject to the effect of fatigue fracture of the plates during their operation. Moreover, the vertical arrangement of the plates increases the dimensions of the device, which requires an increase in the size of the rolling stand.

 There is also known a safety and unloading device of a rolling stand containing a punch and a housing forming a working cavity filled with low-melting metal (lead), as well as an additional cavity enclosed by a shear disk and placed under the working cavity [1].

 The disadvantage of this device is the difficulty of restoring its operability, which requires replacing the shear disk to remove the device from the stand, remove the remnants of low-melting metal and fill the cavity with a new portion of lead. The presence of an additional cavity also necessitates an increase in the vertical dimensions of the rolling stand, which increases its metal consumption and reduces rigidity.

 The objective of the invention is to create a structurally simple, compact and easy-to-use device to reduce the duration of emergency downtime of the mill and reduce the complexity of the restoration work.

 For this, in a safety and unloading device of a rolling stand, including a punch and a housing located under the pressing means, forming a working cavity filled with pressure transmitting material, as well as a destructible element, according to the invention, the housing is formed by a base and a tensile bandage installed with a base covering, and a tensile the bandage is made in the form of a ring, on the outside of which a groove is placed parallel to the axis of the pressing means. As a pressure transmitting material, an elastomer, namely polyurethane, is used. The punch is equipped with a movement limiter made in the form of a cylinder, the axis of which coincides with the axis of the pressing means, and the end face is placed in the hole made in the base of the housing, the retaining ring is provided with a shoulder made on the inner surface of the ring from the side of its supporting end.

 In FIG. 1 shows a diagram of a device with a tensile bandage installed with the coverage of the base; figure 2 - diagram of the bandage made in the form of a ring with a groove; figure 3 - diagram of the distribution of pressure on the inner surface of the working cavity of the device; figure 4 is a diagram of the deformation of a plastic material that transfers pressure, when the destruction of the bandage; 5 is a diagram of a device with a travel limiter, the working cavity of which is filled with an elastomer; figure 6 - diagram of the deformation of the elastomer during the destruction of the retaining ring; Fig.7 is a diagram of a restored elastomer when removing the process load.

 In the space between the pressing means 1 (Fig. 1) and the pillow 2 of the rolling stand, a safety-unloading device is installed, including a punch 3 mounted in a housing formed by a base 4 and a side wall made in the form of a bandage 5 covering the base. The working cavity formed by the punch, bandage and base is filled with a pressure transmitting material 6, which can be used as a plastic material, for example low-melting metal (lead) or elastic material, elastomer (rubber, polyurethane).

 It is advisable to use plastic material to fill the working cavity of the device in the case when significant displacements are necessary for unloading the rolling stand, for example, in the safety devices of blooming rulers. It is advisable to use elastic elastomer materials in safety devices of rolling stands, for the unloading of which significant movement of the rolls is not required, for example, in slabs, roughing stands of plate mills, etc.

 The shape of the bandage in the plan is determined by the plastic properties of the material from which it is made. So, for brittle materials (cast iron, high-carbon steel), the shape of the bandage is allowed to be arbitrary (round, ellipse, square, hexagon, octagonal, flat, with a groove, etc.) and is due to the shape of the free space in the cage to accommodate the safety device, and also the technological conditions for the manufacture of the bandage.

 For ductile materials (low-, medium-carbon steel, non-ferrous metals) the bandage 5 (figure 2) is made in the form of a ring with an inner diameter D and thickness h. On the outer surface of the retaining ring, a groove 7 is made with depth b and a radius of rounding r.

 The device operates as follows.

.When operating the stand in the operating range of technological loads, the punch 3 (figure 3), perceiving the external force Q attributable to the pressing means of the stand, creates pressure in the working cavity
P =

.

, а при выполнении бандажа в виде кольца с проточкой 6 (фиг. 2) - напряжение
σ =

k₁, где H, H₁ - высоты соответственно рабочей полости устройства и его бандажного кольца;
k₁ - коэффициент концентрации напряжений, вызванный проточкой 6.In this case, in the confined space of the working cavity, the pressure transmitting material 6 behaves like a liquid, transmitting pressure to the inner surface of the band 5. Under the action of pressure P, a normal stress occurs in the axial section of the band with a minimum area F _min
σ =

, and when performing a bandage in the form of a ring with a groove 6 (Fig. 2) - voltage
σ =

k ₁ , where H, H ₁ - the height, respectively, of the working cavity of the device and its retaining ring;
k ₁ - stress concentration coefficient caused by groove 6.

, а при использовании бандажного кольца
Q_max =

, происходит разрушение бандажа в опасном сечении, а вместе с ним и разрушение рабочей полости.If the load acting on the pressure means is exceeded, the maximum permissible value
Q _max =

, and when using a retaining ring
Q _max =

, there is a destruction of the bandage in a dangerous section, and with it the destruction of the working cavity.

 As a result, the safety device loses its rigidity, it settles by Δ Н (Fig. 4) at which the external technological force Q, significantly reduced as a result of the rolls roll-off, is balanced by the pressure Po of the remaining part of the material 6.

 To restore the working capacity of the rolling stand, the material to be rolled should be removed from the roll space, the cushion of the rolling rolls should be fixed from vertical movements, the pressure means should be raised and the safety and unloading device replaced. When restoring the bearing capacity of a safety device using plastic material, it is necessary to remove the remnants of the pressure transmitting material, replace the bandage, fill the working cavity of the device with a new portion of material.

 The use of elastomers as a pressure transmitting material simplifies operations when restoring the bearing capacity of safety devices. However, at the same time, their designs need additional distinctive features, which are as follows.

 The punch 3 (Fig. 5), installed in the housing formed by the base 4 and the bandage 5, is equipped with a movement limiter made in the form of a cylinder 8, the axis of which coincides with the axis of the pressing means 1, and the end face is placed in the hole 9 made in the base of the housing. On the inner surface of the bandage there is a collar 10, placed on the side of its supporting end.

 A device using an elastomer operates as follows.

.The maximum technological load at which a bandage of arbitrary shape breaks, taking into account the diameter d of the movement limiter, is
Q _max =

.

, где k₂ - коэффициент, учитывающий влияние бурта 10. В зависимости от размеров бурта k₂ = 0,90...0,95.When using an annular bandage with a groove
Q _max =

where k ₂ - coefficient taking into account the impact of the shoulder 10. Depending on the size of the shoulder k ₂ = 0.90 ... 0.95.

 With fluctuations in the technological load, the value of which does not exceed the maximum permissible value, the shoulder 10 prevents the vertical movement of the bandage 5 along the axis of the device.

 When the load exceeds the maximum permissible value, the bandage collapses in the section weakened by the groove 7. The elastomer 6 (Fig. 6) loses its rigidity and is partially squeezed out into the surrounding space, pushing the destroyed bandage 5. The greatest elastomer deformation is determined by the course Δ Н of the travel limiter 8 and does not exceed maximum elastic deformation of this material, therefore, when the device is completely unloaded, the elastomer 6 completely restores its shape and dimensions (Fig. 7), after which it is necessary to install a new bandage and put the device into operation.

 Among the elastomers recommended for use in safety-unloading devices, rubber and polyurethane should be distinguished.

 Vulcanized rubber, as a cheaper material, it is advisable to apply in the working stands of blank mills, the rigidity of which are not stringent requirements. On the other hand, this elastomer requires minimal gaps between the punch and the bandage, which forces to increase the accuracy and quality of processing the inner surface of the bandage, and also allows the use of bandages made only of brittle material.

 Polyurethanes are hard elastomers, although more expensive materials. Their field of application as a pressure transmitting material in safety and unloading devices of rolling stands covers not only crimping stands of blanking mills, but also roughing stands of plate mills. Polyurethane allows the presence of gaps between the punch and the bandage in 3.. . 4 times larger than vulcanized rubber, and the bandage material can be either brittle or ductile. The latter circumstance can significantly reduce the cost of consumable bandages.

As an example of a specific implementation of the claimed technical solution, a safety-unloading device of the crimping stand of the slab 1150 of the Karaganda metallurgical plant can be given. The installation of an elastomer made in the form of a polyurethane washer of the SKU-PFL-100 brand (E = 58 MPa, μ = 0.493) with dimensions D = 420 mm, d = 160 mm, N = 50 mm allows you to use a retaining ring as a destructible element 40 mm, a height of 70 mm made of steel 45 (GOST 1050-81) with a groove depth of b = 12 mm and a radius of rounding of r = 5 mm. Overall dimensions of the device: height - 120 mm, diameter - 500 mm. The specified parameters ensure the operation of the device in the range of Q _max = 10700 ... 11000 kN with a roll _{extension of} 18 ... 22 mm.

 The use of the device described in the example execution allows to reduce emergency downtime of the mill associated with the restoration of the operability of devices by 60 ... 80%, reduce the complexity of restoration work by 5 ... 8 times and the cost of restoration - by 10 ... 12 time.

 Thus, the set of distinctive features of the claimed technical solution simplifies the design and operation of the device, and also increases its compactness.

Claims (1)

 SECURITY AND UNLOADING DEVICE OF A ROLLING CELL, including a punch and a housing located under the pressing means, forming a working cavity filled with pressure transmitting material, and a destructible element, characterized in that the destructible element is made in the form of an annular bandage mounted on the housing with the material covering , transmitting pressure, while the annular bandage is made with a vertical groove, and as the material, transmitting pressure, an elastomer is used, and the bandage has a shoulder made on its inner surface from the side of the supporting end.

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