Method of manufacture of the flat shape made out of the zirconium-niobium alloys

FIELD: metallurgy industry; methods of manufacture of the flat shape made out of the binary zirconium-niobium alloys.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to the metal forming and may be used at manufacture of the flat shape applied in the capacity of the structural material for the active zones of the atomic reactors. The ingot made out of the binary zirconium-niobium alloy is expose to forging for production of the blank. The forging is exercised in two stages. At the first stage the forging is conducted with heating in the temperature range of existence of β-zirconium. At the second stage the forging is conducted in the upper part of the temperature range of existence of(α+ β)-zirconium at the temperature of not less than 800°С with the reduction rate of the cross-sectional area of no less than 1.3. Then exercise the hot rolling of the workpiece blank ands its cold rolling with the thermal treatments. As a result the invention ensures production of the flat shape with the improved operational properties and the smaller amount of the spoilage under the regulated characteristics.

EFFECT: the invention ensures production of the flat shape with the improved operational properties and the smaller amount of the spoilage under the regulated characteristics.

1 dwg, 1 tbl

 

The invention relates to the field of metal forming, in particular the production of flat profile of binary zirconium-niobium alloys used as structural material for the active zones of nuclear reactors.

To the specified flat profile of zirconium-niobium alloys high demands on the mechanical properties at the operating temperature.

A known method of producing blanks from alloys Zircaloy-2 and Zircaloy-4, including hot compression ingot first β- areas with decreasing cross-sectional area of at least 1.5, and then - in α-areas with decreasing cross-sectional area of not less than 3, quenching in water from a β-field, squeezing in α- areas, cold rolling and heat treatment (French Patent No. 2584097, SS 1/18, SS 16/00, SS 3/06, publ. 02.01.1987).

However, hot compression ingot in α- the field is applicable only to alloys Zircaloy-2 and Zircaloy-4, which due to the specific chemical composition have a high temperature range of existence α-Zirconia. This allows the hot forming of the ingot at temperatures of 740÷790°that is sufficient for industrial applicability in real deformation-time processing options bar.

For binary zirconium-niobium alloys region of existence αqi is Konia limited temperature interval 590÷ 620°C. the Low temperature values of existence α-zirconium binary zirconium-niobium alloys limit the possibility of its industrial applications to deformation processing. Temperature-deformation processing options determine the structural-phase transformations occurring in the alloy, and ultimately the mechanical characteristics of the flat profile, which defines the phase structure.

The closest analogue is the way to obtain sheets of an alloy of zirconium - 2.5% niobium, including the production of billet forging, heating, hot rolling, the intermediate heat treatment, cold rolling and final heat treatment (Patent RF № 2021043, WV 3/00, publ. 15.10.94).

The disadvantage of this method is the lack of regulation of the temperature and deformation parameters upon receipt of the billet forging, resulting in the known method does not provide a uniform development of cast structure of the ingot, the homogeneous formation of structural-phase components of the alloy providing high and stable mechanical properties of flat profile for structural elements of nuclear reactors at the temperature of operation.

The proposed method solves the problem of obtaining a flat profile of zirconium-niobium alloys with improved operating the operating properties and lower marriage on regulated characteristics.

The solution of this problem is to optimize the structural-phase state of the alloy due to the regulation of the temperature and deformation parameters of forging in the process of obtaining billets for hot rolling.

This is achieved in that in the method of obtaining the flat profile of binary zirconium-niobium alloys, including the production of billets forging ingot, hot rolling, cold rolling with intermediate and final heat treatments, obtaining billets from ingots spend hammering in two stages: first by heating in existence β-Zirconia, followed by heating in the upper temperature range of existence (α+β) - zirconium at a temperature of at least 800°With a reduction ratio of cross-sectional area not less than 1.3.

The initial processing stage of forging ingots with heating in the high temperature range of the existence of β-Zirconia allows you to spend considerable preliminary forming of the ingot in the region of low values of resistance to deformation. During hot deformation due to heat exchange with the environment cools, and as a result the deformation resistance - heating of the workpieces. In the deformation warming up with their transition to the two-phase region of existence (α+2 ) - zirconium in the existence region of β-zirconium (α+β)→βand subsequent cooling back β→(α+β) activates the mechanism of polymorphic phase transformations, which determines the structural-phase state of the alloy.

Additional forging zirconium-niobium alloys with heating in the upper temperature range of existence (α+β) - zirconium with the magnitude of deformation, characterized by the reduction ratio of the cross-sectional area of semi-finished products of at least 1.3, leads to the stabilization of structural-phase state of the alloy and, as a consequence, the increase of plasticity and stabilization of mechanical properties, thus providing a flat profile of zirconium-niobium alloys with improved performance characteristics.

The invention is illustrated by the drawing, which shows the values of the mechanical properties of sheets made from billets by the present method with factor μ=1,45 μ=1,3 and closest analogue. The values of the mechanical characteristics of the leaves is given for each individual blanks from which they are made.

The proposed method is implemented in the manufacture of flat profile zirconium-niobium alloy as follows. Forging two ingots of an alloy of zirconium - 2.5% of Yobe carried out with heating in the beta region to 930÷ 980°into strips with dimensions of 122×300 mm and 110×300 mm, Then the strip was heated up to the top of the range the temperature range of existence (α+β) - zirconium (820÷850° (C) and after technological excerpts forged in the size of the billets for hot rolling with an allowance for machining. The reduction ratio of the cross-sectional area of the workpieces in the second stage of forging amounted in the first case μ=1,45, in the second case, - μ=1,3.

Then there was heat treated by heating in (α+β) - region at 750°, followed by machining produced billet of rectangular cross section for hot rolling. Hot rolling of the billet was performed after heating to 750°a sheet with a thickness 4,0-4,mm Then cold rolling with intermediate and final heat treatments received the final sheet thickness 1,5 mm

Comparative analysis was carried out in relation to the values of mechanical properties at the test temperature T=320°With sheets of the same thickness, made by the closest analogue to obtaining billets for hot rolling forging ingots for one stage preheating in β-up to 930÷980°C.

The table shows the statistical data on the mechanical properties of the sheets at the test temperature 320°for comparative and what she used methods of statistical analysis. To test the hypothesis of equality of average values of the compared characteristics used two-sample t-test t-test for testing hypotheses about the equality of variances F-test.

As can be seen from the drawing, the sheet of blanks produced by the present method have a higher plastic properties at a satisfactory level of strength properties. From the results of a comparative statistical analysis presented in the table, it follows that the difference between the properties of the sheets from the billets produced by the present method, and the closest analogue statistically significant: the absolute value of the test value t for all the compared characteristics higher than the critical value of tcrit.

In addition, from the table it follows that the leaves of the billets produced by the present method, have more stable values of mechanical properties: the standard deviation of mechanical properties for these sheets is lower than the standard deviation of similar characteristics for sheets made by the closest analogue. The difference of the dispersion of the values was statistically significant value of F-criterion for yield strength (for leaves of both bars) and relative elongation (for sheets from ingot No. 1) is higher than the critical value of Fcrit.

So about the time, the test results prove that the proposed method allows to optimize the structural-phase state of the alloy due to the regulation of the temperature and deformation parameters of forging in the process of obtaining billets for hot rolling and, thus, solves the problem of obtaining a flat profile of zirconium-niobium alloys with improved performance characteristics.

The inventive method has been successfully tested in industrial conditions.

Table

The results of the statistical analysis of mechanical properties of sheets
MethodT scoreThe average characteristic valueF-scoreThe standard deviation (RMS) characteristics
Tensile strength kgf/mm2Yield strength, kgf/mm2Relates. elongation, %Tensile strength, kgf/mm2Yield strength, kgf/mm2Relates. elongation, %
the ingot No. 1the closest analogue302430,2 0,771,322,94
declare μ=1,4528,322,2the 33.40,720,941,8
the calculated value14,89,84-7,82the calculated value1,131,992,68
the critical value at the significance level of α=0,012,6the critical value at a significance level of

α=0,01
1,72
The ingot No. 2the closest analogue30,424,428,60,981,624,36
declare μ=1,329,623,130,30,91,253,49
the calculated value6,336,14-2,81the calculated value1,191,671,56
the critical value is at a significance level of α =0,012,6the critical value at a significance level of

α=0,01
1,63

A method of obtaining a flat profile of binary zirconium-niobium alloys, including the production of billets forging ingot, hot rolling the billet and cold rolling with heat treatment, characterized in that the receiving billets forging ingots is carried out in two stages, the first of which the forging is carried out with heating in the temperature range of existence β-Zirconia, and the second is in the upper range of the temperature range of existence (α+β) - zirconium at a temperature of at least 800°With a reduction ratio of cross-sectional area of at least 1.3.



 

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FIELD: metallurgy industry; chemical industry; oil-and-gas industry; methods of manufacture of the flat shape made out of the zirconium alloys.

SUBSTANCE: the invention is pertaining to the field of metallurgy and may be used at manufacture of the flat shape applied in the chemical industry and oil and gas industry in the capacity of the structural material in the active zones of the atomic reactors. The billet produced from the ingot by the hot molding is subjected to the thermal treatment and mechanical working. The thermal treatment conduct at the temperature of presence of the field of (alfa+beta)-zirconium within the time interval of 1-3 hours and refrigerating with the speed of not less than 5°C/minute. This thermal treatment may be conducted at the temperature of no less than 800°С. Then exercise the hot rolling, the intermediate thermal treatment, the cold rolling and the final thermal treatment. The hot rolling may be conducted at the temperature not exceeding the temperature of the processing heat treatment. As a result the invention ensures reduction of the prime cost of the manufactured products at the simultaneous increase of stability of their mechanical properties and the technological effectiveness of the alloy.

EFFECT: the invention ensures reduction of the prime cost of the manufactured products at the simultaneous increase of stability of their mechanical properties and the technological effectiveness of the alloy.

3 cl, 3 dwg, 2 ex, 1 tbl

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10 cl 4 ex

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EFFECT: the invention ensures preservation of the metallurgists delivered metal mechanical properties till the moment of the press forming and draw, the possibility of stabilization and optimization of the production process for the metallurgists and the customers of the plates, the increased output of the suitable plates at the press forming, saving of the deficient metal, the increased reliability of the articles of the electro-vacuum production.

2 tbl

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12 cl, 2 dwg

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16 cl, 1 tbl, 6 ex

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3 cl, 1 dwg

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1 tbl, 1 ex

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7 cl, 3 ex

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1 tbl, 1 ex

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2 cl, 6 dwg, 2 tbl

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3 cl, 4 dwg, 2 tbl

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EFFECT: less loss of yield for forged pieces after their mechanical working.

4 dwg, 1 ex

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6 cl, 7 dwg, 2 tbl, 1 ex

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EFFECT: improved factor of metal using, simplified process.

1 ex, 1 tbl

Ring making method // 2286862

FIELD: plastic metal working.

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EFFECT: improved physical and mechanical properties of article in direction of action of maximum loads in operation.

3 cl, 1 ex, 1 tbl

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EFFECT: improved quality of metal of forged pieces.

2 cl, 1 tbl, 1 ex

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EFFECT: improved efficiency of method.

1 tbl, 1 ex

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EFFECT: improved quality of metal, simplified forging process.

2 ex, 1 tbl

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EFFECT: enhanced quality of metal of forging, conversion of dendrite large-grain structure to small-grain one, minimal anisotropy of mechanical properties at low factor of forging reduction ratio, increased efficiency, lowered number of metal heating steps at forging.

4 cl, 8 dwg, 3 ex

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