Manufacturing Method for Tubular Products made of Zirconium-Based Alloy

Abstract

Manufacturing method for tubular products made of zirconium-based alloy includes melting an ingot by multiple vacuum arc remelting, mechanical processing of the ingot, heating, multi-stage hot forging of the ingot for production of a forged piece, subsequent mechanical processing of the forged piece for production of the a round-profile blank, manufacturing of tubular billets, their quenching and tempering, application of a protective coating, heating to a hot pressing temperature, hot pressing, removal of the protective coating, vacuum thermal treatment, multiple cold rolling steps in order to produce tubular products, with intermediate vacuum thermal treatment after each cold rolling, and a final vacuum thermal treatment being carried out at a final size with subsequent final finishing operations. The tubular products can be used as the structural components of a core in water-cooled nuclear reactors. The method can provide increased processibility, high strength, and corrosion resistance of tubular products.

Claims

1. Manufacturing method for tubular products made of zirconium-based alloy containing (% wt.): niobium—0.9-1.7; stannum—0.5-2.0; iron—0.3-1.0; chromium—0.002-0.200, carbon—0.003-0.040, oxygen—0.04-0.15, silicon—0.002-0.15, zirconium—all the rest, including the ingot melting by multiple vacuum arc remelting, mechanical processing of the ingot, heating, multi-stage hot forging of the ingot for production of the forged piece, subsequent mechanical processing of the forged piece for production of the round-profile blank, manufacturing of tubular billets, their quenching and tempering, application of the protective coating and heating to the hot pressing temperature, hot pressing, removal of the protective coating, vacuum thermal treatment, multiple cold rolling with the total deformation degree of 25.6-56.8% per a run and the tubular coefficient of Q=1.0-6.4 in order to produce tubular products, with intermediate vacuum thermal treatment after each cold rolling, and the final vacuum thermal treatment is carried out at the final size with subsequent final finishing operations.

2. The method as claimed in claim 1 characterized in that multi-stage hot forging of the ingot is carried out at the temperature of 980° C. to 720° C. with the total deformation degree of 93% and with intermediate heat-up at the temperature of 890° C. to 850° C.

3. The method as claimed in claim 1 characterized in that tubular billets are produced by drilling of the axial center hole and subsequent boring of the axial center hole in the round-profile blank divided into cut-to-length sections.

4. The method as claimed in claim 1 characterized in that quenching is carried out at the temperature of 1050-1100° C. and tempering—at the temperature of 450-600° C.

5. The method as claimed in claim 1 characterized in that hot pressing of the tubular billet is carried out at the temperature of 640° C. to 600° C. and with the elongation ratio of μ=8.5-9.0.

6. The method as claimed in claim 1 characterized in that vacuum thermal treatment of the tubular billets in the intervals between hot pressing and cold rolling is carried out at the temperature of 605-630° C.

7. The method as claimed in claim 1 characterized in that multiple cold rolling of the tubular billets is carried out with the total deformation degree of 41.8-56.8% per a run and the tubular coefficient of Q=1.0-1.6 for the tubular products of uniform cross-section.

8. The method as claimed in claim 1 characterized in that multiple cold rolling of the tubular billets is carried out with the total deformation degree of 25.6-56.5% per a run and the tubular coefficient of Q=1.0-6.4 for the tubular products of variable cross-section.

9. The method as claimed in claim 1 characterized in that vacuum thermal treatment of the tubular billets in the intervals between cold rollings is carried out at the temperature of 570-630° C.

10. The method as claimed in claim 1 characterized in that the final vacuum thermal treatment of the tubular products is carried out at the temperature of 535-545° C.

11. The method as claimed in claim 1 characterized in that the final vacuum thermal treatment of the tubular products is carried out at the temperature of 600-620° C.

12. The method as claimed in claim 6, characterized in that vacuum thermal treatment of the tubular products is carried out at a residual pressure in the furnace not exceeding 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg.

13. The method as claimed in claim 1 characterized in that chemical and mechanical treatment of the surfaces is carried out at the final size of the tubular products.

Description

EMBODIMENT OF THE INVENTION

[0029] The method is embodied in the following way:

Example 1

[0030] In accordance with the claimed technical solution the manufacturing technology for zirconium tubular products includes the following operations. Melting of the alloy ingot consisting of: niobium 1.05-1.07% (wt.), stannum 1.24-1.27% (wt.), iron 0.31-0.34% (wt.), chromium 0.0025-0.003% (wt.), carbon 0.011-0.019% (wt.), oxygen 0.064-0.065% (wt.), silicon 0.0025-0.0035% (wt.), zirconium—all the rest. The initial alloying components are mixed with electrolytic zirconium powder, and then consumable electrodes are formed and melted by two-stage vacuum arc remelting. The side surface of the ingot is processed mechanically. The ingot is heated to the temperature of 980° C. Multi-stage hot forging of the ingot at the first stage is carried out at the temperature of 980° C., at the last stage—at the temperature of 720° C., with intermediate heating within the temperature range of 890° C. to 850° C.

[0031] The total deformation Σ.sub.ε for hot forging of the ingot is 93%. Heating and intermediate heat-up of the ingot is carried out in the electric resistance-type furnace. Round-profile blanks Ø109×28.5 mm are manufactured by mechanical processing of the forged pieces.

[0032] Tubular billets are produced by drilling of the axial center hole and subsequent boring of the axial center hole in the round-profile blank divided into cut-to-length sections.

[0033] Quenching is carried out at the temperature of 1050-1100° C., and tempering—at the temperature of 450-600° C. The surface roughness of the billets is not more than Ra=2.5 μm. Then the coating is applied on the tubular billets in order to protect them against gas pickup in the course of subsequent heating and hot pressing processes (for example, copper through the use of the copper coating application operation).

[0034] Heating of the tubular billets for hot pressing is carried out in the electric resistance-type furnace. The heating temperature of the tubular billets prior to pressing is within the range of 640° C. to 600° C. Pressing is carried out with the elongation ratio of μ=8.9. Then the copper coating is removed.

[0035] Then the tubular billets are sent for vacuum thermal treatment at the temperature of T=605-630° C. The tubular billets are rolled on the cold reducing mills of HPT, HPTR, KPW type in 5 runs with the total deformation Σ.sub.ε of 41.8 to 56.5% per a run; in this case the tubular coefficient Q is within the range of 1.00-1.6, and the tubular products of uniform cross-section are produced. Intermediate vacuum thermal treatment is carried out within the temperature range of 570° C. to 610° C. The final vacuum thermal treatment is carried out at the temperature of T=535-545° C. or T=600-620° C. Vacuum furnaces with the underpressure level of at least 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg are used.

[0036] The tubes are subjected to a set of operations subsequent to the final annealing and trimming, particularly: jet etching, alkali treatment, grinding of the surface.

[0037] The alloy tubular products Ø12.60×11.24 mm manufactured in accordance with the claimed technical solution are characterized with the following properties (see Table, Example 1).

Example 2

[0038] To be embodied in the same way as Example 1. Composition of the alloy: niobium 0.94-0.97% (wt.), stannum 1.15-1.20% (wt.), iron 0.40-0.46% (wt.), chromium 0.004-0.005% (wt.), carbon 0.008-0.009% (wt.), oxygen 0.10-0.11% (wt.), silicon 0.0055-0.0060% (wt.). The initial alloying components are mixed with zirconium magnesiothermal sponge, and then consumable electrodes are formed and melted by three-stage vacuum arc remelting.

[0039] The tubular products Ø12.60×10.90 mm manufactured in accordance with the claimed technical solution are characterized with the following properties (see Table, Example 2).

Example 3

[0040] To be embodied in the same way as Example 1. Composition of the alloy: niobium 0.90-0.93% (wt.), stannum 1.18-1.22% (wt.), iron 0.82-0.87% (wt.), chromium 0.008-0.009% (wt.), carbon 0.010-0.011% (wt.), oxygen 0.082-0.086% (wt.), silicon 0.0052-0.0058% (wt.). The initial alloying components are mixed with zirconium magnesiothermal sponge, and then consumable electrodes are formed and melted by two-stage vacuum arc remelting.

[0041] The tubular products Ø13.00×11.00 mm manufactured in accordance with the claimed technical solution are characterized with the following properties (see Table, Example 3).

Example 4

[0042] In accordance with the claimed technical solution the manufacturing technology for zirconium tubular products includes the following operations. Melting of the alloy ingot consisting of: niobium 1.06-1.09% (wt.), stannum 1.28-1.30% (wt.), iron 0.65-0.68% (wt.), chromium 0.009-0.011% (wt.), carbon 0.009-0.010% (wt.), oxygen 0.08-0.09% (wt.), silicon 0.009-0.010% (wt.). The initial alloying components are mixed with electrolytic zirconium powder, and then consumable electrodes are formed and melted by two-stage vacuum arc remelting. The side surface of the ingot is processed mechanically. The ingot is heated to the temperature of 980° C. Multi-stage hot forging of the ingot is carried out within the temperature range of 980 to 720° C. with intermediate heat-up within the temperature range of 890 to 850° C.

[0043] The total deformation Σ.sub.ε for multi-stage hot forging of the ingot is 93%. Heating and intermediate heat-up of the ingot is carried out in the electric resistance-type furnace. Round-profile blanks Ø109×28.5 mm are manufactured by mechanical processing of the forged pieces. Tubular billets are produced by drilling of the axial center hole and subsequent boring of the axial center hole in the round-profile blank divided into cut-to-length sections. The surface roughness of the billets is not more than Ra=2.5 μm. Quenching is carried out at the temperature of 1050-1100° C. and tempering at the temperature of 450-600° C.

[0044] Then copper coating is applied on the billets in order to protect them against gas pickup in the course of subsequent heating and hot pressing processes.

[0045] Heating of the billets for hot pressing is carried out in the electric resistance-type furnace. The heating temperature of the billet prior to pressing is within the range of T=640-600° C. Pressing is carried out with the elongation ratio of μ=8.9. Then the copper coating is removed.

[0046] Subsequently the billets are sent for vacuum thermal treatment at the temperature of T=605-630° C. Then the produced billets are rolled at the cold reducing mills of HPT, HPTR type in 6 runs; in this case the tubular coefficient Q is within the range of 1.0-6.4. The variable cross-section of tubular billets is formed through the use of the combined multi-diameter expander with the total deformation degree of Σ.sub.ε=25.6-56.5%.

[0047] Intermediate vacuum thermal treatment is carried out within the temperature range of T=575-590° C. The final vacuum treatment of the tubular products is carried out at the temperature of T=535° C. or T=610° C. depending on the strength requirements. Vacuum furnaces with the underpressure level of at least 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg are used.

[0048] Subsequent to the final vacuum thermal treatment of the tubular products the set of the following final finishing operations is carried out: jet etching, alkali treatment, grinding of the surface.

[0049] Subsequent to formation of the tubular products of variable cross-section from the tubular billet of variable cross-section with different cumulative deformation degree in various sections of the tubular billet the thin-walled and thick-walled sections of the finished pipe have approximately the same cumulative deformation degree providing for uniform mechanical properties of the tubular products after the final vacuum thermal treatment.

[0050] The tubular products Ø12.60×11.24 (10.1) mm manufactured in accordance with the claimed technical solution are characterized with the following properties (see Table, Example 4).

Example 5

[0051] To be embodied in the same way as Example 4.

[0052] The tubular products Ø12.60×10.90 (8.8) mm manufactured in accordance with the claimed technical solution are characterized with the following properties (see Table, Example 5).

INDUSTRIAL APPLICABILITY

[0053] Therefore, the presented manufacturing method for tubular products ensures high strength characteristics and corrosion resistance of the tubular products.

TABLE-US-00001 TABLE Properties of the tubes manufactured of the Zr—Nb—Sn—Fe system alloy in accordance with the claimed technical solution Number of Chemical remeltings/weight Mechanical properties composition of the final Tube σ.sub.b.sup.⊥, σ.sub.0.2.sup.⊥ δ.sup.⊥, σ.sub.0.2.sup.//, Example of the alloy, remelting dimensions, MPa MPa % σ.sub.b.sup.//,MPa MPa No. % (wt.) ingot, tons mm T.sub.test = 20° C. 1 2 3 4 5 6 7 8 9 1 Nb 2 vacuum arc Ø12.60 × 11.24 52.5 46.0 24.6 56.3 43.3 1.05-1.07, remeltings/3.5 FVTT* Sn temperature 1.24-1.27, 540° C., Fe 3 hours 0.31-0.34, Ø12.60 × 11.24 51 36 38 52 35 Cr FVTT* 0.0025-0.003, temperature C 610° C., 0.011-0.019, 3 hours O 0.064-0.065, Si 0.0025-0.0035, Zr- all the rest 2 Nb 3 vacuum arc Ø12.60 × 10.90 55.5 49 22.5 56.5 41.5 0.94-0.97, remeltings/3.5 FVTT* Sn temperature 1.15-1.20, 540° C., Fe 3 hours 0.40-0.46, Cr 0.004-0.005, C 0.008-0.009, O 0.10-0.11, Si 0.0055-0.0060, Zr- all the rest 3 Nb 2 vacuum arc Ø13.00 × 11.00 55.5 48 19 57 44 0.9-0.93, remeltings/1.8 FVTT* Sn temperature 1.18-1.22, 545° C., Fe 3 hours 0.82-0.87, Cr 0.008-0.009, C 0.01-0.011, O 0.082-0.086, Si 0.0052-0.0058, Zr- all the rest 4 Nb 2 vacuum arc Ø12.60 × 11.24 53 47.5 24 55 41.5 1.06-1.09% (wt.), remeltings/3.5 (10.1) FVTT* Sn temperature 1.28-1.30% (wt.), 535° C., 3 Fe hours 0.65-0.68% (wt.), Cr 0.009-0.011% (wt.), C 0.009-0.010% (wt.), O 0.08-0.09% (wt.), Si 0.009-0.010% (wt.), Zr- all the rest 5 Nb 2 vacuum arc Ø12.60 × 10.90 52.5 45.5 32 54.1 40.5 1.06-1.09, remeltings/3.5 (8.8) FVTT* Sn temperature 1.28-1.30, 600° C., Fe 3 hours 0.65-0.68, Cr 0.009-0.011, C 0.009-0.010, O 0.08-0.090, Si 0.009-0.01, Zr- all the rest Corrosion 400° C. Mechanical properties τ = 3600 h δ.sup.//, σ.sub.b.sup.⊥, σ.sub.0.2.sup.⊥, δ.sup.⊥, σ.sub.b.sup.//, σ.sub.0.2.sup.//, δ.sup.//, Weight Example % MPa MPa % MPa MPa % gain, Roughness No. T.sub.test = 20° C. T.sub.test = 350° C. mg/dm.sup.2 Ra, μm 1 10 11 12 13 14 15 16 17 18 1 39.1 28.1 27.0 24.6 31.4 22.2 48.2 149-156 Outer surf. <0.5 Inner surf. <0.8 36 28 15.2 45 29 16 35 150-160 Outer surf. <0.5 Inner surf. <0.8 2 33 30 27 27 31.5 20 40.5 148-152 Outer surf. <0.5 Inner surf. <0.8 3 31.5 30 27.5 24.5 34 21.5 37-39 150-154 Outer surf. <0.5 Inner surf. <0.8 4 35.5 29.5 26.5 27.5 33 24 37.5 147-154 Outer surf. <0.5 Inner surf. <0.8 5 36 27 26 31 30.5 22 36 152-160 Outer surf. <0.5 Inner surf. <0.8 FVTT*—Final Vacuum Thermal Treatment