Preparation method of high-efficiency low-cost hafnium rod

Abstract

The invention discloses a high-efficiency low-cost preparation method of a hafnium rod, which comprises the following steps of: 1, heating a hafnium extruded ingot, preserving heat, and extruding to obtain a hafnium extruded rod blank; 2, carrying out surface treatment on the hafnium extrusion bar blank to obtain a hafnium light bar; and 3, performing one-pass cold deformation on the hafnium light rod by using a rotary swaging machine to obtain a finished product hafnium rod. According to the method, medium-low-temperature extrusion is combined with a large-extrusion-ratio process to replace a traditional process combining multiple high-temperature deformation with annealing, the plasticity potential of metal hafnium is fully released, uniform and fine structures are obtained, the manufacturing efficiency is greatly improved, loss of intermediate procedures is reduced, the cost reduction and efficiency improvement results are remarkable, and the method is suitable for large-scale industrial production. The performance and the appearance size of a final product are adjusted through one-pass cold rotary swaging, operation is easy and convenient, and the method is suitable for mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of hafnium material processing and preparation, and in particular relates to a method for preparing a hafnium rod with high efficiency and low cost. Background Art

[0002] Since hafnium metal and its six isotopes have a large neutron absorption cross-sectional area, excellent mechanical properties, and high temperature and high pressure water corrosion resistance, it is an ideal reactor neutron absorber material. In recent years, with the rapid development of my country's nuclear industry, the demand for neutron absorber materials for various reactors has increased year by year, which requires manufacturers to continuously optimize the manufacturing process to achieve cost reduction and efficiency improvement while meeting performance requirements.

[0003] The traditional preparation method of hafnium rod mainly adopts the method of multiple forging, extrusion, rolling and annealing to achieve uniform organization and fine grain strengthening. The lengthy manufacturing process greatly reduces production efficiency and increases manufacturing costs. Patent No. 201410714543.X discloses a method for preparing hafnium square rods for nuclear reactors. It adopts multiple extrusions, multiple annealings and pass rolling to obtain products that meet the requirements. There are two main problems: 1. The process is cumbersome; the preparation process of this method adopts two extrusions, three annealings, one rolling, and three surface treatments, and the manufacturing cycle is long. 2. Large loss and low yield rate; in the actual preparation process, surface treatment is required before each extrusion and rolling before the next step can be carried out, and the loss in the process is large, resulting in a low final yield rate. Patent No. 201510901500.7 discloses a method for preparing high-quality hafnium rods, which adopts the method of extrusion combined with tube rolling mill rod rolling to prepare. There are several problems: 1. The extrusion temperature is too high, which results in the process only reducing the diameter and homogenizing the structure, but does not fully release the deformation potential of the material and refine the structure to the maximum extent. 2. The use of tube mills for warm rolling of bars to control the performance of the bars has the disadvantages of inaccurate temperature control, slow rolling speed, complex operation, and is not conducive to mass production. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing hafnium rods with high efficiency and low cost in view of the shortcomings of the above-mentioned prior art. The method adopts medium and low temperature extrusion combined with a large extrusion ratio to replace the traditional process of multiple high temperature deformation combined with annealing, which fully releases the plastic potential of metal hafnium, obtains a uniform and fine structure, greatly improves the manufacturing efficiency, reduces the loss of the intermediate process, and has significant results in reducing costs and increasing efficiency.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a hafnium rod with high efficiency and low cost, characterized in that it comprises the following steps:

[0006] Step 1, heating a hafnium extrusion ingot with a diameter of 40 mm to 120 mm to a temperature of 750° C. to 850° C. and then keeping the temperature for 20 min to 60 min, and then extruding the hafnium extrusion ingot after keeping the temperature to obtain a hafnium extrusion rod blank;

[0007] Step 2, surface treating the hafnium extruded rod blank in step 1 to obtain a hafnium polished rod;

[0008] Step 3: Use a rotary forging machine to perform a cold deformation on the hafnium polished rod in step 2, with the deformation amount being 5% to 15%, to obtain a finished hafnium rod.

[0009] The above-mentioned method for preparing a high-efficiency and low-cost hafnium rod is characterized in that the extrusion speed in step 1 is 10 mm / s to 90 mm / s, and the extrusion ratio is ≥8.

[0010] The above-mentioned method for preparing a high-efficiency and low-cost hafnium rod is characterized in that the surface treatment in step 2 includes but is not limited to pickling, turning, grinding or polishing.

[0011] The above-mentioned method for preparing a high-efficiency and low-cost hafnium rod is characterized in that the pickling solution is a mixture of hydrofluoric acid, nitric acid and water in a volume ratio of (3-7):(43-47):50.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1. The present invention adopts medium-low temperature extrusion combined with a large extrusion ratio to replace the traditional process of multiple high-temperature deformation combined with annealing, which fully releases the plastic potential of metal hafnium, obtains a uniform and fine structure, greatly improves manufacturing efficiency, reduces the loss of intermediate processes, and has significant results in reducing costs and increasing efficiency.

[0014] 2. The preparation method of the present invention has no requirements on the state of the extruded ingot (i.e., processed state or cast state). The traditional method requires the ingot to be forged and then used for extrusion.

[0015] 3. The present invention adopts a single cold rotary forging to adjust the performance and appearance size of the final product, which is easy to operate and suitable for mass production.

[0016] The technical solution of the present invention is further described in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0017] Example 1

[0018] A method for preparing a high-efficiency and low-cost hafnium rod in this embodiment comprises the following steps:

[0019] Step 1, heating a hafnium extrusion ingot with a diameter of 40 mm to 750° C. and then keeping it warm for 20 minutes. After the insulation is completed, the hafnium extrusion ingot is quickly placed in an extrusion cylinder with a diameter of 45 mm and starts extrusion. The extrusion ratio is 8 and the extrusion speed is 90 mm / s to obtain a hafnium extrusion rod blank with a diameter of 15.9 mm;

[0020] Step 2: Place the hafnium extruded rod blank in step 1 into a pickling solution to remove the copper / steel sheath, and after removing the sheath, sequentially use a centerless lathe, a centerless grinder, and a polishing machine to perform surface treatment to obtain a hafnium polished rod with a diameter of 15 mm, wherein the pickling solution is a mixture of hydrofluoric acid, nitric acid, and water in a volume ratio of 3:47:50;

[0021] Step 3: Under room temperature conditions, a cold rotary forging machine is used to perform a cold rotary forging deformation on the hafnium polished rod in step 2, with a deformation amount of 5%, to obtain a finished hafnium rod.

[0022] Example 2

[0023] A method for preparing a high-efficiency and low-cost hafnium rod in this embodiment comprises the following steps:

[0024] Step 1, heating a hafnium extrusion ingot with a diameter of 60 mm to 775° C. and then keeping it warm for 30 minutes. After the insulation is completed, the hafnium extrusion ingot is quickly placed in an extruder and extruded. The extrusion ratio is 11 and the extrusion speed is 70 mm / s to obtain a hafnium extrusion rod blank with a diameter of 19.6 mm;

[0025] Step 2: Put the hafnium extruded rod blank in step 1 into a pickling solution to remove the copper / steel sheath, and after removing the sheath, use a centerless lathe, a centerless grinder, and a polishing machine to perform surface treatment to obtain a hafnium polished rod with a diameter of 19 mm, wherein the ratio of the pickling solution is hydrofluoric acid: nitric acid: water is 4:46:50;

[0026] Step 3: Under room temperature conditions, a cold rotary forging machine is used to perform a cold rotary forging deformation on the hafnium polished rod in step 2, with a deformation rate of 7%, to obtain a finished hafnium rod.

[0027] Example 3

[0028] A method for preparing a high-efficiency and low-cost hafnium rod in this embodiment comprises the following steps:

[0029] Step 1, heating a hafnium extrusion ingot with a diameter of 80 mm to 800° C. and then keeping the temperature for 40 minutes. After the heat preservation is completed, the hafnium extrusion ingot is quickly placed in an extruder and extruded. The extrusion ratio is 14 and the extrusion speed is 50 mm / s to obtain a hafnium extrusion rod blank with a diameter of 22.7 mm;

[0030] Step 2: Place the hafnium extruded rod blank described in step 1 into a pickling solution to remove the copper / steel sheath. After removing the sheath, a centerless lathe, a centerless grinder, and a polishing machine are used for surface treatment to obtain a hafnium polished rod with a diameter of 22 mm. The ratio of the pickling solution is 5:45:50 of hydrofluoric acid: nitric acid: water.

[0031] Step 3: Under room temperature conditions, a cold rotary forging machine is used to perform a cold rotary forging deformation on the hafnium polished rod in step 2, with a deformation rate of 9%, to obtain a finished hafnium rod;

[0032] Example 4

[0033] A method for preparing a high-efficiency and low-cost hafnium rod in this embodiment comprises the following steps:

[0034] Step 1, heating a hafnium extrusion ingot with a diameter of 100 mm to 825° C. and then keeping the temperature for 50 minutes. After the heat preservation is completed, the hafnium extrusion ingot is quickly placed in an extruder and extruded. The extrusion ratio is 17 and the extrusion speed is 30 mm / s to obtain a hafnium extrusion rod blank with a diameter of 25.5 mm;

[0035] Step 2: Put the hafnium extruded rod blank described in step 1 into a pickling solution to remove the copper / steel sheath, and after removing the sheath, use a centerless lathe, a centerless grinder, and a polishing machine to perform surface treatment to obtain a hafnium polished rod with a diameter of 25 mm, wherein the ratio of the pickling solution is 6:44:50 of hydrofluoric acid: nitric acid: water;

[0036] Step 3: Under room temperature conditions, a cold rotary forging machine is used to perform a cold rotary forging deformation on the hafnium polished rod in step 2, with a deformation amount of 11%, to obtain a finished hafnium rod.

[0037] Example 5

[0038] A method for preparing a high-efficiency and low-cost hafnium rod in this embodiment comprises the following steps:

[0039] Step 1, heating a hafnium extrusion ingot with a diameter of 120 mm to 850° C. and then keeping the temperature for 60 minutes. After the heat preservation is completed, the hafnium extrusion ingot is quickly placed in an extruder and extruded. The extrusion ratio is 20 and the extrusion speed is 10 mm / s to obtain a hafnium extrusion rod blank with a diameter of 28 mm;

[0040] Step 2: Place the hafnium extruded rod blank in step 1 into a pickling solution to remove the copper / steel sheath, and after removing the sheath, perform surface treatment using a centerless lathe, a centerless grinder, and a polishing machine to obtain a hafnium polished rod with a diameter of 27 mm, wherein the ratio of the pickling solution is 7:43:50 of hydrofluoric acid: nitric acid: water;

[0041] Step 3: Under room temperature conditions, a cold rotary forging machine is used to perform a cold rotary forging deformation on the hafnium polished rod in step 2, with a deformation amount of 15%, to obtain a finished hafnium rod.

[0042] The hafnium bars of Examples 1 to 5 were subjected to tensile tests according to GB / T 228.2 "Tensile Tests for Metallic Materials Part 2: High Temperature Test Methods", and were subjected to 320°C / 21-day tests according to ASTM G2 / G2M "Water or Steam Corrosion Test Methods for Zirconium, Hafnium and Their Alloy Products", and the weight gain results were calculated. The results are shown in Table 1.

[0043] Table 1 Various measured performance indicators

[0044]

[0045] Compared with the hafnium rods prepared by the patents No. 201410714543.X and Patent No. 201510901500.7, the present invention significantly reduces the manufacturing cost while achieving various performance indicators slightly better than the existing hafnium rod preparation technology, and the performance results are stable and the fluctuation range is lower than that of the traditional technology.

[0046] The manufacturing cost of hafnium rods is mainly reflected in two aspects: first, processing cost. Second, yield rate. The process method with patent number 201410714543.X is the conventional technology for preparing hafnium rods. Both methods are calculated based on 200kg of feed, extrusion: 10,000 yuan / furnace; heat treatment 4,000 yuan / furnace; surface treatment 20 yuan / kg. The cost of hot rolling is slightly higher than that of cold forging, both of which are priced at 20 yuan / kg.

[0047] Table 2 Manufacturing cost comparison

[0048]

[0049] As can be seen from Table 2, this patent reduces the manufacturing cost by 62% compared with the patent number 201410714543.X. At the same time, the process that affects the yield rate in the manufacturing process mainly comes from surface treatment. This patent only uses one surface treatment, which can increase the yield rate by 10% to 20%.

[0050] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-efficiency and low-cost hafnium rod, characterized in that: The following steps are involved: Step 1, heating a hafnium extrusion ingot with a diameter of 40 mm to 120 mm to a temperature of 750° C. to 850° C. and then keeping the temperature for 20 min to 60 min, and then extruding the hafnium extrusion ingot after keeping the temperature to obtain a hafnium extrusion rod blank; Step 2, surface treating the hafnium extruded rod blank in step 1 to obtain a hafnium polished rod; Step 3: Use a rotary forging machine to perform a cold deformation on the hafnium polished rod in step 2, with the deformation amount being 5% to 15%, to obtain a finished hafnium rod.

2. The method for preparing a high-efficiency and low-cost hafnium rod according to claim 1, characterized in that: In step 1, the extrusion speed is 10 mm / s to 90 mm / s, and the extrusion ratio is ≥8.

3. The method for preparing a high-efficiency and low-cost hafnium rod according to claim 1, characterized in that: The surface treatment in step 2 includes but is not limited to pickling, turning, grinding or polishing.

4. The method for preparing a high-efficiency and low-cost hafnium rod according to claim 3, characterized in that: The pickling solution is a mixture of hydrofluoric acid, nitric acid and water in a volume ratio of (3-7):(43-47):50.

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