Method of Manufacturing Zirconium Alloy Tubular Products

Abstract

Method of manufacturing zirconium alloy tubular products containing (wt. %): niobium—0.9-1.7; iron—0.04-0.10; oxygen—0.03-0.10; silicon—less than 0.02, carbon—less than 0.02, and zirconium—as the base of the alloy. This includes an ingot melting by multiple vacuum arc remelting, mechanical processing of the ingot, heating, hot working of the ingot, subsequent mechanical processing for the production of tubular billets, heat treatment of the tubular billets, application of a protective coating and heating to a hot pressing temperature, hot pressing, removal of the protective coating, multi-stage cold radial forging, vacuum thermal treatment, multiple cold rolling runs with a total deformation degree of 50-80-% per run and a tubular coefficient of Q=1.0-2.7 with intermediate vacuum thermal treatment after each cold rolling operation, and final vacuum thermal treatment of the resulting tubular products carried out at the final size with subsequent final finishing operations.

Claims

1. The method of manufacturing zirconium alloy tubular products containing (% wt.): niobium—0.9-1.7; iron—0.04-0.10; oxygen—0.03-0.10; 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, hot working of the ingot, subsequent mechanical processing for the production of the tubular billets, heat treatment of tubular billets, application of the protective coating and heating to the hot pressing temperature, hot pressing, removal of the protective coating, multi-stage cold radial forging, vacuum thermal treatment, multiple cold rolling with the total deformation degree of 50-80% per a run and the tubular coefficient of Q=1.0-2.7 with intermediate vacuum thermal treatment after each cold rolling operation, and the final vacuum thermal treatment of the resulting tubular products is carried out at the final size with subsequent final finishing operations.

2. The method as per claim 1 featuring the hot working is carried out by multi-stage forging or screw rolling in the temperature range from 980° C. to 700° C. with a total deformation degree of 67-83% and with intermediate heating at the temperature from 850° C. to 800° C.

3. The method as per claim 1 featuring the tubular billets are produced by drilling and subsequent boring of the axial center hole in the ingot divided into definite cut lengths after the hot working processing.

4. The method as per claim 1 featuring the thermal treatment of the tubular billets is carried out at the temperature from 730° C. to 7850° C.

5. The method as per claim 1 featuring the hot pressing of the tubular billet is carried out at the heating temperature from 750° C. to 650° C. and the elongation ratio of μ=8.9-12.9.

6. The method as per claim 1 featuring the multi-stage cold radial forging of tubular billets is carried out with a rolling draft of 33%.

7. The method as per claim 1 featuring the vacuum thermal treatment of the tubular billets in the intervals between cold rolling and the final vacuum thermal treatment is carried out at the temperature of 565-630° C.

8. The method as per claim 7 featuring the vacuum thermal treatment is carried out at the residual pressure of 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg in the furnace.

9. The method as per claim 1 featuring the chemical and mechanical treatment of the surfaces is carried out at the final size of the tubular products.

Description

EMBODIMENT OF THE INVENTION

[0022] The method is embodied in the following way:

Example 1

[0023] In accordance with the claimed technical solution the technology of manufacturing zirconium tubular products includes the following operations. Melting of the alloy ingot consisting of: niobium—0.97-1.03% wt., iron—0.080-0.010% wt., oxygen—0.040-0.045% wt., silicon—0.003-0.004% wt., carbon—0.0044-0.0046% 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 ingot is processed mechanically. The ingot is heated to the temperature from 980° C. to 930° C. in the electric resistance-type furnace. Multi-stage forging or screw rolling of the ingot after heating is carried out within the temperature range from 980° C. to 700° C. with intermediate heat-up in the electric resistance-type furnace within the temperature range from 850° C. to 800° C. The total deformation Σε in the course of hot working of the ingot lies in the range from 67 to 83%. The ingot is divided into the definite cut length in the size of Ø249×43 mm or Ø199'36.5 mm and processed mechanically, and the tubular billets are obtained by drilling and subsequent boring of an axial central hole in them. Thermal treatment of the tubular billets at the temperatures from 730° C. to 780° C. The roughness of the surface of the tubular billets is no 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. Heating of the tubular billets for hot pressing is carried out in a combined method, first in an induction furnace, and then in an electric resistance furnace to equalize the temperature along the height and cross-section of the tubular billet. The heating temperature of the tubular billet prior to pressing is within the range from 650° C. to 750° C. Pressing is carried out with the elongation ratio of μ within the range from 11.4 to 12.9. Further, the copper coating is removed and preliminary operations for multiple cold rolling are carried out. To reduce metal losses into chips during machining of a tubular billet, multistage radial forging is carried out on an SKK radial forging machine with deformation (ε=33% per pass). Next, the tubular billets are sent for vacuum thermal treatment (T=565° C.). The tubular billets are rolled on cold-rolling mills of the HPT, KPW types in three passes with a total deformation Σε per pass from 60 to 80%, while the tubular coefficient Q lies in the range of 1.0-2.7. Intermediate and finishing thermal treatments are carried out within the temperature range from 590° C. to 630° C. in vacuum with a residual pressure in the furnace not higher than 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg. After the final vacuum thermal treatment of the tubular products at the temperature from 590° C. to 630° C., final finishing operations are carried out: package or jet etching, abrasive processing of the inner surface, grinding and polishing of the outer surface are performed.

[0024] Zirconium alloy tubular products manufactured in accordance with the claimed technical solution are characterized with the following properties (Table 1, Example 1).

Example 2

[0025] In accordance with the claimed technical solution the technology of manufacturing zirconium tubular products includes the following operations. Melting of the alloy ingot consisting of: niobium—0.99-1.08% wt., iron—0.051-0.057% wt., oxygen—0.075-0.080 wt., silicon—0.003-0.004% wt., carbon—0.0032-0.0036% wt., zirconium—all the rest. The initial alloying components are mixed with zirconium magnesiothermal sponge, and then consumable electrodes are formed and melted by two-stage vacuum arc remelting. The ingot is processed mechanically. The ingot is heated to the temperature from 930° C. to 980° C. in the electric resistance-type furnace. Multi-stage forging of the ingot after heating is carried out within the temperature range from 980° C. to 700° C. with intermediate heat-up in the electric resistance-type furnace within the temperature range from 800° C. to 850° C. The total deformation Σε in the course of hot working of the ingot is 67%. The ingot is divided into the definite cut length in the size of Ø249×49 mm and processed mechanically, and the tubular billets are obtained by drilling and subsequent boring of an axial central hole in them. Thermal treatment of the tubular billets at the temperatures from 730° C. to 780° C. The roughness of the surface of the billets is no 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. Heating of the tubular billets for hot pressing is carried out in an induction furnace, and then in an electric resistance furnace to equalize the temperature along the height and cross-section of the billet. The heating temperature of the tubular billets prior to pressing is within the range from 650° C. to 670° C. Pressing is carried out with the elongation ratio μ equal to 8.9. Further, the copper coating is removed. In order to reduce metal losses into chips during machining of a tubular billet, multistage radial forging is carried out on an SKK radial forging machine with deformation (ε=33% per pass). Next, the tubular billets are sent for vacuum thermal treatment (T=565° C.). The tubular billets are rolled on cold-rolling mills of the HPT, KPW types in four passes with a total deformation Σε per pass from 50 to 78%, while the tubular coefficient Q lies in the range of 1.0-2.3. Intermediate thermal treatments are carried out in the temperature range from 570° C. to 600° C. in vacuum with a residual pressure in the furnace not higher than 1.Math.10.sup.−4-1.Math.10.sup.−5 mm Hg. After the final vacuum thermal treatment of the tubular products at the temperature from 590° C. to 595° C., final finishing operations are carried out: package or jet etching, abrasive processing of the inner surface, grinding and polishing of the outer surface are performed.

INDUSTRIAL APPLICABILITY

[0026] Zirconium alloy tubular products manufactured in accordance with the claimed technical solution are characterized with the following properties (Table 1, Example 2).

[0027] 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 remeltings/ Chemical weight of composition the final Tube Mechanical properties of the alloy, remelting dimensions, σ.sub.b.sup.⊥, σ.sub.0.2.sup.⊥, δ.sup.⊥, σ.sub.b.sup.//, σ.sub.0.2.sup.//, δ.sup.//, No. % (wt.) ingot, tons mm MPa MPa % MPa MPa % T.sub.test. = 20° C. 1 niobium - 2 vacuum arc Ø13.58 × 11.70 440-450 360-390 32-38 — — — 0.99-1.08; remeltings/3.5 Ø13.00 × 11.00 iron - Ø9.10 × 7.73 0.051-0.057; Ø10.30 × 8.80  oxygen - Ø9.10 × 7.93 0.075-0.080; Ø8.90 × 7.73 silicon - Ø9.50 × 8.33 0.003-0.004; carbon - 0.0032-0.0036; Zr - all the rest 2 niobium - 2 vacuum arc Ø13.58 × 11.70 440-450 360-390 32-38 — — — 0.99-1.08; remeltings/3.5 Ø13.00 × 11.00 iron - Ø9.10 × 7.73 0.051-0.057; Ø10.30 × 8.80  oxygen - Ø9.10 × 7.93 0.075-0.080; Ø8.90 × 7.73 silicon - Ø9.50 × 8.33 0.003-0.004; carbon - 0.0032-0.0036; Zr - all the rest Corrosion 400° C. τ = Mechanical properties 72 hours σ.sub.b.sup.⊥, σ.sub.0.2.sup.⊥, δ.sup.⊥, σ.sub.b.sup.//, σ.sub.0.2.sup.//, δ.sup.//, Weight No. MPa MPa % MPa MPa % gain, Roughness T.sub.test. = 20° C. T.sub.test = 380° C. mg/dm.sup.2 Ra, μm 1 190-210 160-190 38-48 190-220 108-130 58-63 10-14 Outer surf. < 0.4 Inner surf. < 0.8 2 190-210 160-190 38-48 190-220 108-130 58-63 10-14 Outer surf. < 0.4 Inner surf. < 0.8