RU2238817C2 - Method for manufacture of bolts from low thermal conductivity metals - Google Patents

Abstract

FIELD: plastic working of metals, in particular, manufacture of fastening parts with heads from, for example, titanium alloys, may be used in mechanical engineering and aviation equipment.

SUBSTANCE: method involves heating basic blank to forming temperature and providing hot forming by vertical pattern, with forming of bolt core being provided by extrusion process including uniform flowing of metal into extrusion head over funnel-shaped surface. Pressure is applied to blank through pressing washer. Portion of blank is left in container of extruder for further forming of bolt head.

EFFECT: increased efficiency, simplified process owing to reduced number of operations and increased cyclic strength of bolt.

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Description

The invention relates to the processing of metals by pressure, and in particular to methods for the production of fasteners with heads, for example, from titanium alloys, and can be used in mechanical engineering and aircraft.

In the field of metal forming, there is a known method of manufacturing products, mainly fasteners, from hardly deformable low-plastic titanium alloys, which consists in hydrogenating a workpiece and deforming it in a heated state by extruding a workpiece from (α + β) -titanium alloys at a temperature of 20 ° -50 ° C above the temperature of the onset of recrystallization of the hydrogenated alloy, followed by vacuum annealing, combined with recrystallization annealing, at a temperature of 10 ° -100 ° C below the temperature of the (α + β) → β transition (AS No. 18210 09, IPC B 21 J 5/06, publ. 20.07.95). The disadvantages of this method are the complexity of the process and the inability to obtain a diameter of the heads greater than (1.8 ... 2) the diameter of the rod part of the bolt blank.

The closest in technical essence to the claimed method is a method of manufacturing bolts of titanium alloys, including annealing, rapid heating to a quenching temperature, quenching in water, hot shaping of the bolt head, cooling in air and aging, and heating during aging is carried out at a speed of 120 ° ± 10 ° C to a temperature of 780 ° ± 10 ° C, hot shaping of the bolt head is carried out after aging at a temperature not exceeding the aging temperature (AS No. 1233523, IPC C 22 F 1/18, publ. 20.05.97). The disadvantages of this method are the difficulty (or impossibility) of the selection of process parameters for alloys other than VT16 alloy, the inability to obtain a head diameter greater than (1.8 ... 2) the diameter of the core part of the bolt blank.

The problem solved by the present invention is to increase the technologically permissible ratio of the diameter (or weight) of the head to the diameter (or weight) of the shaft part of the bolt, increase the stability of the mechanical properties of the bolts, increase the cyclic resistance of the bolts.

When using the present invention, the following technical results are achieved:

- increased technologically permissible ratio of the diameter of the head to the diameter of the rod part of the bolt;

- increased stability of the mechanical properties of the bolts;

- increased cyclic resistance;

- increased productivity of the process;

- increased utilization of the material.

To solve the problem and achieve the technical result in a known method of manufacturing bolts of titanium alloy, which consists in heating the initial billet to the temperature of forming and hot forming, according to the invention, the forming is carried out in a vertical manner, the rod is formed before molding the head of the bolt by extrusion, the metal is sent to extruding head on a funnel-shaped surface, the pressure on the workpiece is carried out through a press washer, while leaving it in the container part of the workpiece for subsequent head design.

A comparative analysis of the proposed solution with the prototype shows that the claimed method differs from the known one in that the hot forming is carried out in a vertical manner, the bolt shaft is obtained by extrusion, the metal is directed along the funnel-shaped surface into the extruder head, the pressure on the workpiece is carried out through a press washer, and for the shaping of the bolt head in the container of the extruder leaves part of the workpiece for its subsequent shaping. Thus, the claimed method meets the criteria of the invention of “novelty”.

When analyzing the known technical solutions, no methods were found that have features that match the distinguishing features of the proposed method, which allows us to conclude that it meets the criterion of “inventive step”.

Using a vertical shaping scheme, the heat loss zone from the workpiece to the extruder parts is localized in the contact area of the lower end surface of the workpiece with the press washer, which prevents cooling of the side and upper surfaces of the workpiece before extrusion, thereby subsequently avoiding surface defects in the form of cracks, sunsets, delaminations and maintain a uniform structure. By forming the core by extrusion, they provide a directional texture of the workpiece, thereby increasing the cyclic resistance of the bolt. By directing the metal into the extruder head on a funnel-shaped surface, they provide a smooth, uniform outflow of material, which eliminates surface defects and uneven mechanical characteristics over the volume of the workpiece. By exerting pressure on the workpiece through the press washer, a blank-free workpiece is obtained, thereby increasing the metal utilization rate and reducing labor intensity, since removal of the burr (end burr) is not required. Leaving in the container part of the workpiece for the subsequent molding of the bolt head, an initial larger diameter of the press residue is obtained for the subsequent molding of the head, which allows for its subsequent upsetting to obtain significantly larger ratios of the diameters of the head and the rod than in the known methods.

The proposed method of manufacturing bolts is implemented as follows.

Billet 1 (Fig. 1) with a diameter of D = 10 ... 30 mm and a height of H = (1 ... 10) D mm of VT-16 titanium alloy is heated to a temperature of 50 ° ... 70 ° C below the phase temperature ( α + β) → β transition, namely 770 ° ... 790 ° C, is transferred to the container 2, not allowing cooling, and installed on the press washer 3, based on the press stamp 4; from above the extruder head 5 is pressed to the container (Fig. 2) and the press washer 3 moves the press washer 3 upward at a speed of 0.05 ... 0.20 m / s relative to the container and the extruder head pressed against it, extruding part of the workpiece into the channel of the extruder head, and leaving the other part in the container and inlet funnel of the extruder head. After cooling the workpiece in the extruder, a thermal gap forms around it and it is removed from the extruder, after which the process is repeated with the next workpiece. In the process of extrusion, stresses of all-round compression act in the bulk of the workpiece, which prevents the development of cracks in the workpiece material, despite the high degree of shear deformation of the material. In the vertical extruder layout, the workpiece cools before extruding only through the contact surface with the press washer, i.e. only through the surface, which is not subject to change during extrusion, due to this, no chilled areas are formed on the lateral surface, which, if they appeared, would lead to the formation of surface defects on the workpiece. The effect of cooling is manifested the stronger, the lower the thermal conductivity of the material, because the heat lost from the surface in a material with low thermal conductivity is not compensated by the supply of heat from the volume of the workpiece. These supercooled surface areas have a higher strength inherent in low temperatures, and when extruded, they are either pressed into the area of the hot material, causing damage, and (or) damage the surface of the extruder channel.

Using the proposed method provides, in comparison with the existing method, the following advantages:

- productivity increase;

- simplification of technology by reducing the number of operations;

- increase the cyclic resistance of the bolt.

Claims (1)

A method of manufacturing bolts from a material with low thermal conductivity, including heating the initial billet to the forming temperature and hot forming, characterized in that the forming is carried out in a vertical pattern, while the forming of the bolt rod is carried out by extrusion, ensuring uniform flow of metal into the extrusion head on the funnel-shaped surface, pressure on the workpiece is carried out through a press washer, while part of the workpiece is left in the container of the extruder for subsequent molds the formation of the bolt head.

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