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产品名称： Industrial Zirconium
Classification:Industrial zirconium
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所属分类：Industrial zirconium
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Introduction
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1. Overview
Zirconium (Zirconium) element symbol is Zr, located in the IV-B group element of the periodic table, silver-white metal. It has a high melting point, moderate density, good strength and plasticity matching, and a small thermal neutron absorption cross-section. It is an important structural material in the nuclear industry; zirconium, like titanium, has excellent corrosion resistance in many acid and alkali media. Therefore, zirconium is an excellent chemical corrosion-resistant structural material.
The main products of industrial pure zirconium include plates, tubes, forgings, bars, welding wires, etc., which are used to make pressure vessels, heat exchangers, towers, agitators and other structural parts. The working temperature can reach 300℃～375. ℃.
Usually, zirconium ore contains hafnium, and it is difficult and costly to separate hafnium from zirconium ore. Zirconium in the nuclear industry needs to remove the hafnium element. Industrial pure zirconium is composed of 95.5%-99.2% zirconium and hafnium, among which hafnium, the maximum content allowed in the standard is 4.5%. As we all know, under most corrosion-resistant application conditions, the element hafnium will not significantly change the mechanical properties and corrosion resistance of zirconium. Therefore, the content of hafnium is allowed to be maintained at a natural level in the standard, which can greatly reduce the cost.
Industrial pure zirconium processing products mainly have two chemical composition levels, one is low-oxygen grade, the Chinese brand is Zr-1, and the American brand is UNS R60700. Its high plasticity is mainly used for explosive composite materials and also used in Fields with high requirements for plasticity; the other is high oxygen grade, the Chinese brand is Zr-3, and the American brand is UNS R60702; each has excellent corrosion resistance, and there is only a slight difference between the two in mechanical properties. .
2. Chemical composition and mechanical properties of industrial zirconium
In 2009, my country’s newly formulated national standard "Zirconium and Zirconium Alloy Grades and Chemical Composition" is basically consistent with the chemical composition and mechanical properties of industrial pure zirconium specified in the American advanced ASTM/ASME material standard. my country’s Zr-1 is equivalent to R60700 and Zr-3 in the United States are equivalent to R60702 in the United States.
3. Physical properties of industrial pure zirconium
Industrial zirconium density: 6.59g/cm3; melting point: 1852℃; boiling point: 3580℃; phase transition temperature: 860℃～870℃; above the phase transition temperature, it is a body-centered cubic lattice (β phase), Below the phase transition temperature, it is a dense hexagonal lattice (α phase).
4. Processing and heat treatment of industrial pure zirconium
The mechanical properties of the two grades of industrial pure zirconium largely depend on the purity of the sponge zirconium used for smelting. As the content of impurity elements (especially oxygen, nitrogen and iron) rises, the tensile strength and hardness increase rapidly .
Industrial pure zirconium has good processing properties under hot conditions, similar to industrial pure titanium, and can be subjected to pressure processing such as forging, extrusion, and rolling. Industrial pure zirconium also has good cold workability. Plates, pipes, and wires can be cold rolled or drawn, and its cold workability is equivalent to industrial pure titanium.
The processing technology of zirconium depends on the basic properties of zirconium and the special requirements for zirconium components. The main processes for processing the most widely used plates and seamless pipes are: preparation of consumable electrodes, melting and casting, forging, hot rolling or hot extrusion (tube blanks), cold working, and finishing.
The vacuum consumable electric arc furnace smelting method is the most common method of zirconium industrial production. Only by adopting the correct method of adding additional elements, a suitable industrial sponge zirconium and a reasonable casting system can we obtain high-quality ingots.
The microstructure and performance of industrial pure zirconium processing materials can be achieved by controlling the amount of processing deformation and annealing process system. Therefore, adopting a reasonable deformation and annealing process system is an important process measure to ensure the performance of processed materials.
The billeting of the ingot is generally carried out in the β phase zone, the secondary forging temperature is lower than the billeting temperature, and the final forging temperature is generally not less than 700℃. The hot rolling temperature is similar to the secondary forging temperature, and the extrusion temperature is lower. In order to obtain plates and pipes with good comprehensive performance, the total deformation rate of cold rolling before the finished product should be more than 50%.
The annealing of cold-worked materials must be carried out in a vacuum furnace, and the vacuum degree should be higher than 4x10-2Pa. The intermediate annealing temperature is 500°C to 700°C. The vacuum annealing temperature of the plate is 600℃～750℃, and the holding time is 60min. The annealing temperature of the pipe is 550℃～650℃. The zirconium clad steel plate should be delivered in a stress-relieving state after explosive compounding. The annealing temperature is 540℃～600℃, and the holding time is 3h～5h.
5. Welding performance of industrial pure zirconium
Zirconium has much better weldability than alloy steel and aluminum. It can be welded by fusion welding, brazing, solid welding and other methods. One of its common welding methods is TIG welding.
The solubility of iron in zirconium is very low, zirconium and steel are not suitable for direct fusion welding. Iron shall not be mixed in the welding of zirconium on the zirconium-lined container and the zirconium composite plate container, so the welding structure should adopt a special structure like titanium.
Zirconium can be welded with titanium, tantalum, etc., but there are not many applications in engineering. The weldability of zirconium is similar to that of chromium-nickel stainless steel. The thermal expansion coefficient of zirconium is small, only about 2/3 of titanium, 1/2 of nickel and ferritic steel, 1/3 of copper and austenitic steel, and 1/4 of aluminum. It is among various engineering metal materials. The lowest, so the welding deformation is small; the elastic modulus of zirconium is small, about 1/2 of that of steel and nickel, so the welding residual stress is small; the welding crack sensitivity of zirconium is low. Zirconium has a high melting point, so the welding site must be kept clean.
The mechanical properties of zirconium are very sensitive to intermittently dissolved elements such as nitrogen, oxygen, carbon and hydrogen. In addition to controlling the content of these elements in the zirconium material and welding wire, special attention should be paid to the welding parts and welding wire before welding. To prevent the entry of these elements, the purity of argon should not be less than 99.998%.
Zirconium is highly active and has a strong affinity for hydrogen, oxygen, and nitrogen in the ambient gas. When the heat-affected zone of the weld pool and the welding seam during cooling and the backside are at a temperature above 350-400℃ Should be placed under inert gas protection. Zirconium oxide has a high solubility in zirconium, and slag inclusion is usually not easy to produce in the weld. Zirconium welds have the possibility of producing pores, so pollution during welding should be avoided to prevent hydrogen from entering the zirconium molten pool.
6. Formability of industrial pure zirconium
The annealed industrial pure zirconium sheet can be easily bent in ordinary press brakes or forming processing equipment, reaching a bending radius of 5T at room temperature and 3T at 200℃～300℃. When cold forming a zirconium tube, it is recommended to use a bending radius close to 3 times the outer diameter. For smaller bending radii, it is necessary to perform thermoforming at a temperature of 200°C to 425°C, or use special bending techniques. When bending the zirconium tube, springback may be encountered due to its work hardening. In addition, during the bending process, both the internal and external surfaces should maintain a certain tension to prevent the pipe from twisting and the pipe wall from becoming thinner.
7. Machining performance of industrial pure zirconium
The work hardening tendency of zirconium is obvious. The machining should adopt slow speed, large feed rate, and sufficient coolant and lubricant. Hard alloy is commonly used for cutting tools, high-speed steel can also be used, and silicon carbide wheels are used for grinding wheels.
8. Corrosion resistance of industrial zirconium
Zirconium is a passivation metal. The standard electrode potential of zirconium is – 1.539V. Zirconium has a strong affinity for oxygen and can react with oxygen in the air at room temperature to form a dense oxide film with strong adhesion. The oxide film protects the base metal from chemical or mechanical damage, and can resist certain highly corrosive environments including various inorganic acids (such as hydrochloric acid, sulfuric acid, nitric acid, etc.), alkalis, and most organic acids (such as acetic acid, formic acid, etc.). Kind of corrosion of salt solution and molten alkali.
Zirconium has excellent corrosion resistance in all concentrations and temperatures up to the boiling point of hydrochloric acid, and it is not prone to crevice corrosion, pitting corrosion and stress corrosion. Zirconium can withstand the boiling point in sulfuric acid and is higher than the boiling point, with a concentration of 70%. When the concentration is lower than 65%, a small amount of oxidizing ions in sulfuric acid will not affect the corrosion resistance of zirconium. When the concentration of sulfuric acid is lower than 40%, zirconium allows a large amount of oxidizing ions to exist. Zirconium has good corrosion resistance at 150°C and 90% nitric acid containing oxidizing ions, and at 200°C and 30-70% nitric acid containing oxidizing ions and chloride ions. Zirconium is resistant to corrosion in organic acids, but it is not resistant to corrosion in hydrofluoric acid, concentrated sulfuric acid, concentrated phosphoric acid, aqua regia, bromine water, hydrobromic acid, fluorosilicic acid, calcium hypochlorite, and fluoroboric acid. It is not resistant to corrosion in oxidizing chlorides, such as copper chloride and ferric chloride solutions, but it is resistant to corrosion in reducing chloride solutions.
9. The safety of zirconium processing
There is a major preventive measure that must be considered when processing zirconium. It is non-toxic, but due to its exothermic reaction with oxidizing elements such as oxygen, zirconium is easy to catch fire. Large pieces of thin plates, thick plates, rods, tubes and ingots can be heated to a very high temperature without catching fire, but small chips are easily ignited and burned at high temperatures. Therefore, it is necessary to prevent a large amount of hoarding of scraps or other small pieces of zirconium, and care should be taken to store this material in non-flammable containers and enclosed areas. Zirconium scraps should be removed from the machine frequently and placed in a suitable storage container.
An effective way to store zirconium scraps is to place them in a container with water, with a layer of oil on top of the water to prevent evaporation. It is important to keep all storage containers well covered to prevent stray sparks from igniting the zirconium. If zirconium catches fire, do not use ordinary fire extinguishers or water. Dry sand, powdered graphite or special metal powder should be used.
10. Application of industrial zirconium:
In the production of hydrogen peroxide, acrylic acid and acrylic fiber: all zirconium heat exchanger tubes replace graphite heat exchangers.
In the production of methacrylate from sulfuric acid: high-pressure vessels, towers, heat exchangers, piping system pumps, and valves are all made of zirconium.
Sulfuric acid reboiler made of zirconium is used in the production of butanol.
In the production of azo dye coupling reaction, zirconium heat exchanger, pump and stirrer are used.
In the production of food and medicine, the use of zirconium equipment not only solves the corrosion problem of hydrochloric acid, but also ensures the purity of food and medicine.
In the production of nitric acid, the zirconium tower and zirconium regenerator replace the original 316L, titanium and FRP.
In the production of low-pressure carbonylation acetic acid, many containers, heat exchangers, pump valves, etc. use zirconium materials.
To sum up, industrial pure zirconium has excellent corrosion resistance, welding, processing and other comprehensive properties, and can be used to produce plates, pipes, bars, wires, forgings, castings and other products. , Fertilizer, metallurgy, shipbuilding and other industrial fields.
key word：
Sponge zirconium
Hafnium oxide
Magnesium chloride
ammonium salt
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