RU2249630C2 - Method for thermal straightening of products - Google Patents

Abstract

FIELD: plastic working of metals, in particular, methods for thermal straightening of annular flange products, may be used for manufacture of high-precision thin-walled pipes.

SUBSTANCE: method involves locating annular product, mandrel, pressure member and pressure rod, with linear expansion coefficient of mandrel and pressure member exceeding that of product and pressure rod; establishing initial gap between cover and pressure member end for creating of compression force; providing heating, during which straightening of product flange is performed simultaneously with diametrical gauging of ring.

EFFECT: increased efficiency by providing simultaneous thermal straightening of flange of product and gauging of ring in diametrical direction.

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Description

The invention relates to the field of metal forming, in particular to methods of thermal dressing of products, and can be used in the manufacture of thin-walled pipes with high accuracy.

A known method of thermal dressing of products in which the coefficient of thermal expansion of the workpiece material is less than the coefficient of thermal expansion of the mandrel (AS USSR No. 205866, C 21 D 9/06). The disadvantage of this method is the inability to edit the product in the axial direction.

A known method of thermal straightening of a tubular billet, in which the ends of the workpiece after installation on the mandrel are fixed on it using female rings having a coefficient of thermal expansion less than the coefficient of thermal expansion of the material of the mandrel (AS USSR No. 945203, C 21 D 9/08 )

There is a method of thermal straightening of flat tools (circular saws, cutting and slotting cutters, hacksaw blades, etc.): they are clamped between two faceplates, which are pulled together with bolts or a wedge. After each tempering, the nuts of the clamping device are turned up to the end or the wedge is tightened, which allows to gradually reduce the deformation of the tool (p. 212 I.V. Friger Heat treatment of alloys: Reference book. - L.: “Mechanical engineering, Leningrad department”, 1982. - 304 p.). The disadvantage of this method is the inability to control the dressing force in the axial direction, which can lead to cold welding of the product to the plates.

The closest is the method of thermal dressing of products, including installing the product on an element (mandrel), pressing it with a spacer sleeve (clamp) through the pressure rod with a cover with a wedge, heating and cooling, while the linear expansion coefficients of the element (mandrel) and spacer sleeve (clamp) more than the coefficient of linear expansion of the pressure rod (AS USSR No. 247985, C 21 D 9/06).

An object of the invention is the simultaneous thermal dressing of the product flange and calibration of the ring in the diametrical direction.

The specified technical problem is achieved due to the fact that in the method of thermal dressing of annular flange products, including the product, the mandrel, the clamp and the pressure rod, while the linear expansion coefficients of the mandrel and the pressure are greater than the linear expansion coefficient of the product and the pressure rod, set between the cover and the end face of the clamp the initial clearance to create a compressive force, and when heated, simultaneously edit the product flange and calibrate the ring in the diametrical direction.

The invention is illustrated in the drawing (cross section of the device).

The method is carried out using a thermal dressing device, consisting of a base 1, on which a cylindrical mandrel 2 is mounted and in which a pressure rod 3 is fixed. A cover 4 is mounted on the pressure rod 3, which is fixed by a wedge 5. A product 6 is installed on the mandrel 2, which is a ring with a flange, on the flange of which a clamp 7 is mounted, made in the form of a cup mounted coaxially with a cylindrical mandrel 2. Between the upper end of the clamp 7 and the cover 4, an initial clearance "A" is established, requiring I have to create a certain axial compression force for straightening the flange products.

The method is as follows.

The product 6 is mounted on a cylindrical mandrel 2, and the coefficient of linear expansion of the material which is greater than the coefficient of linear expansion of the material of the product. A clamp 7 is installed on the flange of the product 6. A cover 4 is mounted on the pressure rod 3 and fixed by a wedge 5. Moreover, the coefficient of linear expansion of the material of the rod is less than the coefficient of linear expansion of the material of the clip. Between the upper end face of the clamp 7 and the cover 4, the initial clearance "A" is set, which is necessary to create a certain axial compression force during heating when dressing the product flange.

During heating, due to the difference in the coefficients of thermal expansion of the material of the pressure rod 3 and the pressure 7, the initial clearance "A" decreases to 0 mm, after which a certain compression force is created to edit the flange of the product 6. Simultaneously, the product 6 is edited in the diametrical direction beyond due to the greater coefficient of thermal expansion of the material of the mandrel 2 compared with the coefficient of thermal expansion of the material of the product 6.

For example: Hardening of a product made of maraging steel of the ChS35 grade is carried out at a temperature of 800 ° C and holding for 1 hour on a mandrel of steel 12X18H10T with a clamp of steel 12X18H10T with a length of 150 mm and a pressure rod made of steel 40X with a working length of 140 mm. The initial clearance "A" between the cover and the end face of the clip is set equal to 0.4 mm

When heated, the initial gap “A” decreases between the cover and the end face of the clamp due to the difference in the coefficients of thermal expansion of the materials of the clamp and the pressure rod, and at a temperature of 760 ° C the gap disappears. With a further increase in temperature, the pressure rod through the cover and the pressure on the product flange creates an increasing axial force, which at a temperature of 800 ° C will be 50 kg. This force does not lead to plastic deformation of the device elements, but is sufficient for straightening the product flange with a thickness of 0.15 mm. In the absence of an initial clearance "A", the axial force of the clamp will be 600 kg, which will lead to cold welding of the product to the clamp.

At the same time, thermal straightening of the product in the diametrical direction occurs due to a larger coefficient of thermal expansion of the mandrel material.

The presence in the device of the initial clearance "A" will improve the quality of products with high-temperature dressing.

Claims (1)

The method of thermal dressing of annular flange products, including installing the product on the mandrel, pressing it with a clamp through the pressure rod by a cover, subsequent heating and cooling, while the linear expansion coefficients of the mandrel and pressure are greater than the linear expansion coefficient of the product and the pressure rod, characterized in that between the cover and the end face of the clamp sets the initial clearance to create an axial compression force, and when heated, simultaneously edit the flange and calibrate the ring in the diametrical direction.