RU2445399C1 - Manufacturing method of flat hafnium profile - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves hot forging of ingot, machining of surface, hot rolling, cold rolling at several stages with intermediate and final nonoxidation heat treatments. Hot forging is performed by heating to 1000-1200°C and total drawing of not more than 2.2 at each stage. Hot rolling is performed by heating to 900-1000°C with total drawing to 18 and single crimping of not more than 30%. Cold rolling is performed at several stages with deformation at each stage of 20-50% with intermediate and final nonoxidation heat treatments at 700-800°C.

EFFECT: improving mechanical properties of hafnium and quality of hafnium profile surface.

3 cl, 1 tbl, 1 ex

Description

The invention relates to the field of non-ferrous metallurgy, in particular for forging and rolling production, and is intended to obtain a flat profile of hafnium, used as a structural material in the active zones of nuclear reactors.

A known method of manufacturing metal plates from hafnium brand HFE-1, including electron beam melting ingot, hot forging, processing of forgings by cutting, heating in an oven in air to 1000 ° C, rolling in a mill with cold rolls, final heating for rolling to a temperature of 800 ° C, final cold rolling with a total deformation of about 55%, grinding the workpiece to obtain plane-parallel plates with a thickness of 5.5 mm, cutting the plates to size, grinding in a solution for chemical polishing (R.V. Azhazha, M.P. Starolat, A. A. Vasiliev and p Effect of annealing on the properties of the hot rolled hafnium in collection of Nuclear Science and Technology, 2008, №1 Series:.... The vacuum clean materials, superconductors (17), M., p.27).

The disadvantages of this method are: low surface quality of the rolled products due to repeated heating in air for hot rolling and the need for an expensive grinding operation to remove the surface substandard layer.

The closest analogue of the claimed invention is a known method for the manufacture of metallic hafnium, including ingot smelting, heating the ingot to 950-1000 ° C, ingot forging, surface machining, heating to a temperature of 930 ° C in argon, hot rolling of a hafnium ingot in the temperature range of 830 -930 ° C, intermediate heating after 15-20% reduction at a speed of 0.508-0.838 m / s, cold rolling with one-time deformations of 7%, intermediate annealing at a temperature of 780 ° C and final heat treatment in the temperature range of 840-870 ° C in flowed ie 1-1.5 hours. (Electron beam melting and hafnium pressure treatment. Overview, issue 8 (78), M., VNIINM, 1982, p.21-22).

The known method has a relatively low efficiency and a long production cycle due to:

- low heating temperature for forging (950-1000 ° C), which does not allow forging with high hoods and leads to an increase in the number of heatings;

- a large number of heatings after 15-20% reduction during hot rolling.

The proposed method solves the problem of increasing technical and economic indicators for obtaining a flat profile from hafnium.

This is achieved by the fact that in the method of manufacturing a flat profile of hafnium, including hot forging of the ingot, mechanical surface treatment, hot rolling, cold rolling in several stages with intermediate and final non-oxidative heat treatments, the forging is carried out with heating to 1000-1200 ° C and a common hood up to 2.2 at each stage, hot rolling is carried out with heating to 900-1000 ° C with a total hood of up to 18 and single reductions of up to 30%, cold rolling is carried out with deformation at each stage of 20-50%, and the intermediate and final term processing is carried out at 700-800 ° C.

Carrying out forging with heating to 1000-1200 ° C promotes the ability to carry out a general hood up to 2.2 at each stage, ensuring the rational use of energy-power parameters of the forging equipment.

Hot rolling with heating to 900-1000 ° C with a total hood of up to 18 and single reductions of up to 30% in each pass allows hot rolling without the use of intermediate cutting and heating operations, thereby increasing the efficiency of obtaining a flat profile from hafnium.

Carrying out cold rolling with total deformations of 20-50% also provides hafnium rolled sheet with high efficiency and high surface quality due to intermediate and final heat treatments in an oxidizing environment at 700-800 ° C, which provide high technological properties of the material for carrying out cold rolling processes in the claimed conditions without the formation of defects, as well as obtaining as a result of a flat profile with a set of properties presented to structural elements from hafnium for active zones of nuclear reactors.

This eliminates the loss of metal associated with the need to remove the substandard layer with micro-tears and cracks. Thus, the invention allows to reduce the cost of manufacturing a flat profile by reducing the rejection of finished products by mechanical properties and defects on the surface of the products.

It is optimal to carry out forging with single reductions of up to 45%, this allows you to get forgings with high surface quality from large-sized hafnium ingots with a diameter of up to 320 mm.

Before cold rolling, it is preferable to conduct heat treatment at 700-800 ° C, this helps to improve the technological properties of the hot-rolled material.

Example

A hafnium ingot with a diameter of 320 mm was heated in a resistance furnace to a temperature of 1060 ° C, the heated ingot was forged on a forging press with a total hood of about 2.0 at each stage.

Then the forging was heated to 920 ° C for hot rolling, which was carried out on a two-roll sheet mill. A total hood was provided by about 15 without heating, single reductions of 14–24%.

The hot rolled sheet was heat treated at a temperature of 750 ° C. Then it was cold rolled in several stages with a strain of about 45% at each stage. Between stages of cold rolling, heat treatment was carried out in an oven at a temperature of about 750 ° C, and then final heat treatment at the same temperature.

The resulting sheets were analyzed to determine their properties. The analysis data are given in the table.

Parameter Established requirements Received Characteristics Surface quality scratches, nicks, risks, dents with a depth of not more than 0.1 mm requirements are met Thickness mm 0.6 ± 0.05 0.58 ÷ 0.63 Endurance limit σ _in , MPa not less than 300 467 ÷ 524 (for 32 tests) Yield strength σ _0.2 , MPa not less than 150 217 ÷ 262 (for 32 tests) Elongation δ ₅ ,% not less than 12 average 46% (for 32 tests)

As the results showed, hafnium sheets comply with established requirements.

At the same time, the claimed method in comparison with the prototype does not involve heating after every 15-20% reduction in argon, which reduces the cost of production and shortens the production cycle.

Currently, the Chepetsk Mechanical Plant OJSC is conducting pilot-industrial production of a hafnium flat profile using the inventive method.

Claims (3)

1. A method of manufacturing a flat profile of hafnium, including hot forging of an ingot, mechanical surface treatment, hot rolling, cold rolling in several stages with intermediate and final non-oxidative heat treatments, characterized in that the forging is carried out with heating to 1000-1200 ° C and a common hood up to 2.2 at each stage, hot rolling is carried out with heating to 900-1000 ° C with a total hood of up to 18 and single compressions of not more than 30%, cold rolling is carried out with deformation at each stage of 20-50%, and the intermediate and final ones moobrabotki carried out at 700-800 ° C. 2. The method according to claim 1, characterized in that the forging is carried out with single reductions of not more than 45%. 3. The method according to claim 1, characterized in that before cold rolling, heat treatment is carried out at 700-800 ° C.