Manufacturing Method for Zirconium Alloy Tubular Products

Abstract

Manufacturing method for zirconium alloy tubular products containing (% wt.): niobium—0.9-1.7; iron—0.10-0.20; oxygen—0.10-0.20; silicon—less than 0.02, carbon—less than 0.02, zirconium—the alloy base. The method includes melting an ingot by multiple vacuum arc remelting, mechanical processing of the ingot, heating, multi-stage hot forging for production of the forged piece, subsequent mechanical processing of the forged piece for production of tubular billets with vacuum thermal treatment, 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 with a total deformation degree of 58-74% per run and a tubular coefficient of Q=1.18-2.01, with intermediate vacuum thermal treatment in order to produce tubular products, and final vacuum thermal treatment being carried out at the final size with subsequent final finishing operations.

Claims

1. Manufacturing method for zirconium alloy tubular products containing (% wt.): niobium—0.9-1.7; iron—0.10-0.20; oxygen—0.10-0.20; silicon—less than 0.02, carbon—less than 0.02, zirconium—all the rest, including the ingot melting by multiple vacuum arc remelting, mechanical processing of the ingot, heating, multi-stage hot forging for production of the forged piece, subsequent mechanical processing of the forged piece for production of tubular billets with vacuum thermal treatment, 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 58-74% per a run and the tubular coefficient of Q=1.18-2.01, with intermediate vacuum thermal treatment in order to produce tubular products, 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 700° C. with the total deformation degree of up to 93% and with intermediate heating at the temperature of 850° C. to 800° C.

3. The method as claimed in claim 1 characterized in that thermal treatment of the forged piece is carried out at the temperature of 1050° C. to 1100° C. with subsequent water cooling.

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

5. The method as claimed in claim 1 characterized in that vacuum thermal treatment of the tubular billets prior to hot pressing is carried out at the temperature of 570° C. to 600° C.

6. The method as claimed in claim 1 characterized in that hot pressing of the tubular billet is carried out at the temperature of 600° C. to 620° C. and the elongation ratio of μ=8.9.

7. The method as claimed in claim 1 characterized in that vacuum thermal treatment of the tubular billets after hot pressing is carried out at the temperature of 565° C. to 595° C.

8. The method as claimed in claim 1 characterized in that intermediate vacuum thermal treatment of the tubular products between multiple cold rollings and the final vacuum thermal treatment of the tubular products are carried out at the temperature of 565° C. to 595° C.

9. The method as claimed in claim 5, characterized in that vacuum thermal treatment of the tubular billets and products is carried out at the residual pressure in the furnace of 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg.

10. 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

[0023] The method is embodied in the following way:

Example

[0024] 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—1.00-1.03% wt., iron—0.116-0.119% wt., oxygen—0.120-0.125% wt., silicon—0.002-0.003% wt., carbon—0.003-0.005% wt., zirconium—all the rest. The initial alloying components are mixed with zirconium magnesiothermal sponge, and then consumable electrodes are formed and melted by three-stage vacuum arc remelting. The ingot is processed mechanically. The ingot is heated to the temperature of 930° C.-980° C. in the electric resistance-type furnace. Multi-stage forging of the ingot after heating is carried out within the temperature range of 980° C. to 700° C. with intermediate heat-up in the electric resistance-type furnace within the temperature range of 850° C. to 800° C. The total deformation Σε in the course of hot deformation processing of the ingot was up to 93%. The forged piece is heated to the temperature of 1050° C.-1100° C. with subsequent water cooling. The forged piece is cut into cut-to-length sections and processed mechanically to the size of 0109×28.5 mm; then the tubular billets are manufactured by drilling and subsequent boring of the axial center hole.

[0025] Vacuum thermal treatment is carried out at the temperature of 570° C. to 600° C. Surface roughness of the billets is not more than R.sub.a=2.5 μm. Then copper 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. Heating of the tubular billets for hot pressing is carried out in the induction furnace. The heating temperature of the tubular billets prior to pressing is within the range of 600° C. to 620° C. Pressing is carried out with the elongation ratio of μ=8.9. Then the copper coating is removed and vacuum thermal treatment is carried out at the temperature of 565° C. to 595° C. The tubular billets are rolled on the cold reducing mill of HPT, 2HPTS, KPW type in 4 runs with the total deformation Σε of 58% to 74% per a run, in this case the tubular coefficient Q is within the range of 1.18-2.01. Intermediate thermal treatment is carried out within the temperature range of 565° C. to 595° C. in vacuum at the residual pressure in the furnace not exceeding 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg.

[0026] Subsequent to the final vacuum thermal treatment of the tubular products at the temperature of 565° C. to 595° C. package or jet etching, abrasive processing of the inner surface, grinding and polishing of the outer surface are performed.

INDUSTRIAL APPLICABILITY

[0027] The zirconium alloy tubular products manufactured in accordance with the claimed technical solution are characterized with the following properties (Table 1).

[0028] Thus, the presented tube manufacturing method enables to produce tubular products with high corrosion resistance, stable characteristics of mechanical properties and deformation resistance

TABLE-US-00001 TABLE 1 Properties of the tubes manufactured of the Zr—Nb 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.b.sup.//, σ.sub.0.2.sup.//, δ.sup.//, of the alloy, remelting dimensions, MPa MPa % MPa MPa % No. % wt. ingot, tons mm T test = 20° C. 1 niobium - 3 vacuum arc Ø9.10 × 7.73 500-520 440-460 26-31 — — — 1.00-1.03; remeltings/1.2 iron - 0.116-0.119; oxygen - Ø9.10 × 7.93 500-520 430-440 28-31 520-540 353-392 45-48 0.120-0.125; silicon - 0.002-0.003; carbon - Ø9.50 × 8.33 500-520 440-460 30-33 — — — 0.003-0.005; zirconium - all the rest Corrosion 400° C. Mechanical properties τ = 72 h σ.sub.b.sup.⊥, σ.sub.0.2.sup.⊥, δ.sup.⊥, σ.sub.b.sup.//, σ.sub.0.2.sup.//, δ.sup.//, Weight MPa MPa % MPa MPa % gain, Roughness No. T test = 380° C. mg/dm.sup.2 Ra, μm 1 206-216 176-186 37-42 — 118-127 — 14-15 Outer surf. <0.4 Inner surf. <0.8 196-206 167-186 38-42 216-225 118-127 62-68 15-17 Outer surf. <0.4 Inner surf. <0.8 196-206 176-186 40-44 225 118-127 61-67 15-17 Outer surf. <0.4 Inner surf. <0.8