RU2699428C1 - Method of forging rolling rings - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal forming and can be used in making forged rolling rings from hard-to-form steel. Ring wall is reduced along perimeter by means of striker and mandrel with ring turn. For the first turn of ring reduction of its wall is performed with value of relative reduction, decreasing from value of relative reduction at the beginning of forging. Value of relative reduction is determined from the given expression. During subsequent turns of the ring, its walls are uniformly squeezed.

EFFECT: as a result, production of rings without cracks.

1 cl, 1 dwg, 1 ex

Description

The invention relates to the processing of metals by pressure, namely, to press forging briskly steel rolled rings on a mandrel.

Known methods of forging rolling rings for several revolutions on the mandrel, and the hammer and the mandrel can have a curved shape, which improves the processing of metal (see article Balyasny IM Study of the deformation of the workpiece during rolling. Forging and stamping, 1965, No. 12, p 5; USSR AS No. 685407, BI No. 34, 1979; AS No. 432962, BI No. 23, 1974; RF patent No. 2279328, BI No. 19, 2006, etc.). The disadvantage of these methods is that they apply a uniform compression mode along the perimeter of the ring without taking into account the increase in deformation resistance when cooling the forgings during its turns. This can lead to cracking due to a decrease in the ductility of the metal during cooling.

The closest in technical essence to the proposed one (prototype) is a method of forging rolled rings using a striker and a mandrel, which includes alternately varying portioned compression of the ring wall along the perimeter with rotation between the crimps (see I. Balyasny, Metal deformation during rolling of forgings such as bandages. - In the book Forging of large forgings, part II, under the editorship of V.N. Trubin (Moscow: Mechanical Engineering, 1965, p. 288). In this method, at the beginning of a new revolution of the ring, the amount of compression is brought to the set gradually, after 3-5 feeds of the workpiece. The advantage of the prototype, in contrast to analogues, is the use of an alternating compression mode, which allows you to take into account the change in the properties of the metal during its deformation and cooling. However, it is envisaged to increase the reductions, which contradicts the laws of change in the resistance to deformation from temperature (see reference book Polukhin P.I., Gun G.Ya., Galkin AM Resistance to plastic deformation of metals and alloys. M: Metallurgy, 1983. P. 26) which consist in increasing the resistance to deformation with a drop in temperature as a result of cooling the forgings. It can also lead to cracks in the forging, its rejection and increased metal consumption.

The problem solved by the invention lies in the fact that during forging of rolled rings from hard-to-deform steels with an incorrectly selected compression mode, cracks in the forging may occur, which is a defect and will increase the consumption of metal.

The technical result of the proposed invention is to reduce the likelihood of cracks in the forging and to save metal due to the use of a decreasing compression mode for one revolution of the ring, taking into account the laws of increasing the resistance to deformation of the metal when it is cooled.

The technical result is achieved by the fact that in the method of forging of rolled rings using a striker and a mandrel, which includes alternately varying portionwise compression of the ring wall along the perimeter with rotation between the compressions, the decreasing compression mode for one revolution of the ring is used, and the compression of the ring wall is determined from the expression:

where ε is the relative decreasing compression;

ε ₀ = 0.12 ... 0.15 - relative compression at the beginning of forging;

a = 0.04 ... 0.06 - coefficient taking into account the increase in resistance to deformation of the metal when it is cooled;

ϕ = 0 ... 2π is the angle of rotation of the ring relative to the initial position.

The essence of the invention lies in the fact that a decreasing compression mode is established during forging of rolled rings, taking into account the increase in the deformation resistance of the metal when it is cooled.

In FIG. 1 depicts forging patterns according to the proposed method with a decreasing compression mode for one revolution of the ring (pos. 4) and according to known methods (pos. 5). Also in FIG. 1 is indicated: 1 - striker; 2 - initial blank in the form of a ring; 3 - mandrel.

Formula (1) for calculating the compression mode depending on the angle of rotation of the ring ϕ was obtained taking into account the patterns of change in deformation resistance as a function of temperature, which consist of an increase in deformation resistance with a decrease in temperature as a result of cooling of the forgings by an exponential dependence (see reference book P.I. Polukhin. , Gun G.Ya., Galkin AM Resistance to plastic deformation of metals and alloys. M: Metallurgy, 1983. P. 26).

As an example of the implementation of the proposed method, we consider the rolling of the ring with an external diameter of 1560 mm, an internal diameter of 540 mm, a height of 400 mm from a workpiece with an external diameter of 1530 mm, an internal diameter of 400 mm and a height of 400 mm from high-carbon hard-deformed steel containing 1.2 ... 1, 4% C; 0.2 ... 0.5% Si; 0.5 ... 0.8% MP; 1.4 ... 1.7% Cr; 0.6 ... 0.9% Ni; 0.1 ... 0.3% Mo; 0.12% V; 0.044% Nb (RF patent 2540241. Steel for the manufacture of forged rolling rolls / Potapov A.I., Orlov G.A., Shestakova E.N., Orlov A.G .; claimed. 10.31.2015; publ. 02.10.2015 . Bull. No. 4).

For this steel, the forging mode with relative compressions of the ring wall of 10-15% to avoid cracking is recommended, the temperature range of forging is 1150-900 ° С (see article Application of steels of hypereutectoid grades for forging hot-rolling rolls / Potapov A.I., Shestakova E.N., Orlov G.A., Belikov S.V. / Ferrous metals. - 2015. - No. 2. - P. 33-37).

From these recommendations, the relative compression of the ring wall (ε = Δh / h ₀ , where Δh is the absolute compression; h ₀ is the initial thickness of the ring wall) at the beginning of forging, ε ₀ = 0.12 was selected, and the subsequent relative reductions at the first revolution of the ring were determined by formula (1) at a = 0.06 in accordance with an increase in deformation resistance with a drop in temperature as a result of cooling of the forgings (see the above article by Potapov A.I. et al.).

Subsequent ring revolutions during rolling to obtain the required ring sizes were carried out according to traditional technology with a uniform compression mode (see pos. 5, Fig. 1).

The technical result of the claimed invention is to obtain forged rolled rings from hard-to-deform steels without cracks, which increases the yield and provides metal savings.

Claims (5)

A method of forging by rolling a ring of hardly deformable steel, comprising compressing the wall of the ring around the perimeter by means of a striker and a mandrel with rotating the ring, characterized in that during the first revolution of the ring, compression of its wall is carried out with a relative compression value ε decreasing from the relative compression value at the beginning of forging ε ₀ = 0.12-0.15, while the value of ε is determined from the expression ε = ε ₀ ⋅exp (-ɑϕ), where ɑ = 0.04-0.06 - coefficient taking into account the increase in the resistance to deformation of the metal when it is cooled;        ϕ = 0-2π - the angle of rotation of the ring relative to the initial position, and with subsequent turns of the ring, uniform compression of its wall is carried out.

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