Category: Zirconium alloy

Exploring the Properties of Zirconium for Use in Nuclear Reactors

Zirconium is an important material used in the production of nuclear fuel rods for nuclear reactors. In this article, we will explore zirconium’s unique properties that make it an ideal choice for use in nuclear reactors, as well as some of the challenges and concerns associated with its use.

Physical and Chemical Properties of Zirconium Fuel Rods

Zirconium fuel rods are composed primarily of zirconium metal, which has several important physical and chemical properties that make it an ideal material for use in nuclear reactors. These include:

  • High melting point: Zirconium has a high melting point of 1855°C, which makes it able to withstand the extreme temperatures generated by nuclear fission reactions.
  • Low thermal neutron absorption: Zirconium has a low cross section for absorbing thermal neutrons, which are the neutrons that slow down as they collide with other atoms. This makes it an ideal material for use as cladding around fuel pellets, as it does not interfere with the nuclear reactions taking place inside the fuel pellets.
  • Excellent corrosion resistance: Zirconium is highly resistant to corrosion, particularly in high-temperature, high-pressure environments such as those found in nuclear reactors.
  • Good mechanical properties: Zirconium has good mechanical properties, including high strength, ductility, and toughness, which help to ensure the integrity and safety of the fuel rods.

Advantages of Using Zirconium as Nuclear Fuel

The use of zirconium as a nuclear fuel has several advantages, including:

  • High thermal conductivity: Zirconium has a high thermal conductivity, which helps to efficiently transfer heat away from the fuel pellets to the coolant in the reactor.
  • Low neutron absorption: As mentioned earlier, zirconium has a low cross section for absorbing thermal neutrons, which allows the neutrons to pass through the cladding and interact with the fuel pellets, resulting in sustained nuclear reactions.
  • Excellent corrosion resistance: Zirconium is highly resistant to corrosion, which is important in preventing the release of radioactive materials into the environment.
  • Readily available: Zirconium is abundant in the earth’s crust and is relatively easy to mine and process, making it an economically viable choice for use in nuclear reactors.

Disadvantages of Using Zirconium as Nuclear Fuel

However, there are also some disadvantages to using zirconium as nuclear fuel, including:

  • Potential for hydrogen buildup: When zirconium is exposed to water at high temperatures, it can react with the water to produce hydrogen gas, which can build up inside the fuel rods and potentially lead to explosions or other safety issues if not properly managed.
  • Radioactive waste: Like all materials used in nuclear reactors, zirconium fuel rods eventually become radioactive and must be properly disposed of once they are no longer usable. This can be a time-consuming and expensive process.
  • Regulatory concerns: The use of zirconium as nuclear fuel is subject to strict regulatory oversight to ensure the safety of workers, nearby communities, and the environment. Compliance with these regulations can be costly and time-consuming for nuclear power plant operators.

Safety Concerns and Regulations

Due to the potential hazards associated with the use of zirconium as nuclear fuel, there are several safety concerns and regulations in place to ensure the safe operation of nuclear reactors. These include:

  • Inspections and monitoring: Nuclear power plants are subject to regular inspections and monitoring by regulatory agencies to ensure compliance with safety standards.
  • Emergency preparedness plans: Nuclear power plants must have detailed emergency preparedness plans in place in case of an accident or other emergency situations.
  • Worker training and protection: Nuclear power plant workers must undergo extensive training on safety procedures and must be provided with appropriate protective gear and equipment when working with radioactive materials.

Conclusion

Zirconium is a unique and important material in the production of nuclear fuel rods. Its high melting point, low thermal neutron absorption, excellent corrosion resistance, and good mechanical properties make it an ideal choice for use in nuclear reactors. However, there are also some challenges and concerns associated with its use, including the potential for hydrogen buildup, radioactive waste, and regulatory compliance. As such, the use of zirconium as nuclear fuel is subject to strict safety regulations and oversight to ensure the safety of workers, nearby communities, and the environment.

For more information about zirconium or other metals, please visit https://www.samaterials.com/.

Application and Prospect Analysis of Zirconium

Zirconium is a metal material with superior physical and chemical characteristics. It is used in a variety of industrial, scientific, and technological applications. The following is an analysis of the uses and prospects of zirconium from different angles.

Zirconium Used in Nuclear Energy

Zirconium is one of the essential elements in the realm of nuclear energy due to its physical characteristics. Fuel rods and structural components for nuclear reactors can be manufactured with zirconium alloys. The high melting point, corrosion resistance, high strength, and high-temperature stability of zirconium alloys make them ideal materials for producing nuclear reactor fuel rods. Statistics show that every year, roughly 50 tons of zirconium alloys are used in the production of nuclear reactors worldwide.

Zirconium Used in Aerospace Industry

Zirconium is frequently utilized in the aerospace industry due to its superior mechanical qualities and strong temperature endurance. Zirconium alloys can be used to create components for aero engines such as blades, nozzles, and combustion chambers. Zirconium alloys can be utilized for a variety of components, including spacecraft hulls, turbines, and combustion chambers. They have exceptional qualities that can enhance spaceship performance, including lightweight, high strength, and high-temperature durability.

Zirconium Use in Medical Field

Zirconium is used extensively in the medical industry. Drugs can be radiolabeled using the zirconium isotope zirconium-89 for the detection and management of certain malignant disorders. Zirconium alloys have high strength, strong biocompatibility, and corrosion resistance, which can increase long-term durability and biological compatibility, and they can also be utilized to make artificial joints, dental implants, and other biomedical materials.

Zirconium Used in Chemical Industry

The chemical sector additionally employs extensive use of zirconium. Zirconium compounds are used in a variety of industries, including oxidants, antiseptics, catalyst supports, and catalysts. Because zirconium alloys offer great corrosion resistance, high-temperature stability, and long-term use in hostile chemical environments, they can also be utilized to make reactors, heat exchangers, reactors, and other equipment.

Zirconium Used in Electronics

Zirconium is also widely used in the field of electronics. Zirconium alloys and zirconates can both be used to create capacitors and battery electrodes, respectively. The primary areas of zirconium used in the electronics sector are nanotechnology and high-temperature superconducting materials. Zirconium can be used as an addition to boost the superconducting temperature and current density of high-temperature superconducting materials. Zirconium is also frequently utilized in nanotechnology and is capable of producing nanotubes, nanocrystals, and nanomaterials.

Zirconium Used in Metal Surface Coating

To stop corrosion and increase the hardness of metal surfaces, zirconium can be utilized in the production of surface coatings. Zirconium alloys can also be used to create metal coatings that are resistant to corrosion at high temperatures and have great corrosion resistance. Zirconium alloys are also perfect for producing drill bits, saw blades, and other tool materials due to their wear durability, and corrosion resistance.

Related reading: Where Zirconium is Used?

Conclusion

To sum up, zirconium has significant uses in the sectors of nuclear energy, aircraft, medical treatment, the chemical industry, electronics, and metal surface coating due to its exceptional physical and chemical qualities. The sustainable development of zirconium and the creation and use of ecologically friendly materials will also become popular trends as people’s awareness of environmental protection rises, further broadening the material’s potential uses.

4 Methods for Making Metal Zirconium

Zirconium and its alloys not only have good machinability, moderate mechanical strength, and high corrosion resistance, but also have a low neutron cross-section. In the nuclear energy industry, they are widely used as structural materials for water reactors. Zirconium widely exists in zircon, so most methods of preparing metal Zr use zircon as a raw material for extracting zircon. This article will mainly introduce four methods for purifying zirconium.

Metal Thermal Reduction Method

The reducing agents used in the thermal reduction method are mainly calcium and magnesium.

(1) Calcithermic reduction

Using ZrO2 as raw material and calcium as a reducing agent, the reduction reaction is carried out at 1273-1373K under vacuum. The reduction product is a powdery mixture of Zr, CaCl2, CaO, and Ca, which can be pickled, washed with water, filtered, dried, and sieved to obtain metal zirconium.

(2) Magnesium reduction method

The magnesium reduction method mainly includes steps such as the preparation of zirconium tetrachloride, purification, magnesium reduction, and vacuum distillation. Chloride zirconium dioxide or zircon sand to obtain zirconium tetrachloride, purify, remove impurities such as SiCl4, TiCl4, AlCl3, FeCl3, and then use molten magnesium to reduce ZrCl4 to obtain a mixture of metal zirconium, magnesium, and magnesium chloride, and finally, Zirconium metal is obtained by distillation and purification.

Zirconium Ores

Hydrodehydrogenation

This method uses the reversible absorption characteristics of zirconium to hydrogen to prepare zirconium powder. At a certain temperature, zirconium and zirconium alloys absorb hydrogen to form hydrides or solid solutions. When reaching a certain level, the material will produce microcracks, become brittle, and contain a lot of hydrogen. Such powder is called zirconium hydride powder. Zirconium hydride powder is dehydrogenated under high temperature and vacuum conditions to obtain zirconium powder. After years of improvement and promotion, this method has become the main method for producing zirconium powder.

Molten Salt Electrolysis

Metals or alloys that are difficult to electrodeposit in an aqueous solution usually use molten salt electrodeposition. Insoluble anodes are usually used, stainless steel or other refractory metals are used as cathodes, and molten salts of electrodeposited metals and alkali metal chlorides or fluorides are used as electrolytes. During the electrolytic reduction process, they are decomposed by the electrolytic metal molten salts. and deposited at the cathode.

Direct Electro-Deoxidation Method

The direct electro-deoxidation method uses a single or mixed metal oxide as the raw material, presses it into a block as the cathode, removes the oxygen in the cathode by electrolytic deoxidation, and obtains a metal element or alloy with low impurity content in a high-temperature molten salt, also known as FFC Law. The metals successfully prepared by the FFC method include Zr, Hf, Be, Mg, Ca, Ba, V, Nb, W, Fe, and Cu.

Among the four methods, the magnesium reduction method and hydrogenation-dehydrogenation method are the main production methods in the industry.

For more information about zirconium materials, please visit https://www.samaterials.com/.

 

 

The Importance of Surface Coatings for Zirconium Alloy Cladding

Safety Issues in The Application of Zirconium Alloys

In the past few decades, zirconium alloy cladding has been successfully applied to light water reactors (LWR), and has shown good radiation resistance and corrosion resistance. However, a major problem in the application of zirconium alloys in stacks is that they react violently with water vapor at high temperatures, and when the temperature is greater than 1200 °C, a large amount of hydrogen and heat will be released. After the Fukushima nuclear power accident in Japan, the safety of nuclear power has once again been placed in front of all nuclear workers. How to further improve the safety and reliability of light water reactor nuclear fuel elements under accident conditions has become an urgent problem to be solved. Research and development directions include accident-resistant fuel cores and accident-resistant cladding materials.

surface-coatings-for-zirconium-alloy-cladding

Cladding Material for Zirconium

The accident-resistant cladding material has good thermodynamic properties, which can improve the reaction kinetics of zirconium and water vapor and reduce the hydrogen release rate. The development of this material is mainly reflected in two aspects: one is to improve the high-temperature oxidation resistance and strength of the zirconium alloy cladding; the other is to develop non-zirconium alloys with high strength and oxidation resistance. This paper discusses the research on the surface coating of zirconium alloy cladding for the former.

The main advantage of the application of coated zirconium cladding is economical. The technical challenge it faces is to meet various performance requirements of the fuel cladding and components without changing the size of the fuel cladding. During long-term operation, the coating should have certain stability under corrosion, creep, and abrasion conditions.

Research Status of Zirconium Alloy Cladding Surface Coating

The anti-oxidation coating technology on the surface of zirconium alloy is the main method to improve the anti-oxidation ability of the surface of zirconium cladding. The outer surface of the zirconium alloy is coated with a layer of material to enhance the wear resistance and high-temperature oxidation resistance of the cladding, thereby improving the accident resistance of the zirconium cladding under normal working conditions and accident conditions. At present, some preliminary screening results have been obtained in international research on the surface coating of zirconium alloy cladding, and the coating materials mainly involve MAX phase and metal Cr.

MAX-phase coating

A series of studies have shown that:

  1. The essence of the MAX phase coating is the dressing effect, and the key to the problem is to solve the diffusion of oxygen atoms to the zirconium substrate.
  2. No matter whether in a fast neutron reactor or thermal neutron reactor, under the three activation time conditions, the activity of MAX phase material is similar to that of SiC, but three orders of magnitude lower than that of 617 alloys.
  3. The thickness of the MAX phase coating should be controlled at 10~30 μm to limit the loss of neutrons.
  4. Ti3SiC2 shows better prospects than Ti2AlC as a candidate material for MAX-phase coatings for high-temperature nuclear energy applications.
  5. At room temperature, the radiation resistance of Ti3AlC2 is better than that of Ti3SiC2, and the radiation stability of the two MAX phase materials at 600 ℃ is better than that at room temperature.
Metal Cr Coating

A series of studies have shown that:

  1. The high-temperature oxidation resistance of the coated zirconium alloy is obviously better than that of the Zr-4 substrate.
  2. The high-temperature oxidation resistance of the coated zirconium alloy is significantly stronger than that of the zirconium alloy substrate, and the Cr-coated zirconium cladding has better ductility.
  3. The metal Cr coating has good high-temperature oxidation resistance and can be used as a candidate coating material for accident-resistant zirconium alloy cladding.

For more information about zirconium materials, please visit https://www.samaterials.com/70-zirconium.html.

If you are interested in coating materials, you can find more information at https://www.sputtertargets.net/.

 

Separation of Zirconium and Hafnium by Solvent Extraction

Solvent extraction of zirconium and hafnium is one of the common methods for separating zirconium and hafnium. Compared with other zirconium and hafnium separation methods (such as pyrolysis separation and solvent extraction separation), this method has the advantages of large production capacity, simple process and easy to achieve continuously.

Principle

The extraction agents used for the separation of zirconium and hafnium mainly include ketone extractants, neutral phosphorus-containing extractants and amine extractants.

A commonly used ketone extractant is methyl isobutyl ketone (MIBK), which can form a neutral extract with hafnium thiocyanate and is preferentially extracted into the organic phase.

Methyl isobutyl ketone 3D ball
Methyl isobutyl ketone 3D ball. Source: Wikipedia

A typical neutral phosphorus-containing extractant is tributyl phosphate (TBP), which is preferentially extracted into the organic phase through the coordination of oxygen atoms in chemical bonds with zirconium metal atoms to form a neutral extract compound Zr(NO3)4•2TBP.

Ball and stick model of Tributyl phosphate
Ball and stick model of Tributyl phosphate. Source: Wikipedia

The commonly used amine extractant is trioctylamine (TOA). Trioctylamine forms an extract with zirconium ions in an acidic medium, and is preferentially extracted into the organic phase.

Process flow

There are three extraction processes: MIBK, TBP, and N235.

MIBK extraction

It uses ZrCI4 as raw material, adds water and NH4CNS ingredients. MIBK preferentially extracts hafnium, leaving a large amount of zirconium in the aqueous phase. This is the earliest extraction process used to separate zirconium and hafnium, and it is adopted by major producers of zirconium and hafnium such as the United States, France, Germany, and Japan.

TBP extraction

There are two aqueous feed systems for this process: nitric acid, and a mixed acid of nitric & hydrochloric acid. The former is to convert the product of zircon decomposed by alkali fusion method into nitric acid aqueous phase feed liquid, and use TBP to preferentially extract zirconium; the latter use Zr-CI4 as raw material, add water, nitric acid and hydrochloric acid as ingredients, and then use TBP to preferentially extract zirconium.

The separation coefficient of zirconium and hafnium in the TBP extraction process is large, and the number of extraction stages is small, and atomic-level zirconium oxide and hafnium oxide can be obtained at the same time. However, the water-phase feed liquid is highly corrosive, and the emulsification problem in the extraction process has not been completely solved, thus affecting its popularization and application.

N235 extraction

First, the zircon is decomposed by alkali fusion method, and the product is washed with water to remove silicon, and then leached with sulfuric acid to obtain a sulfuric acid solution of zirconium, and then the zirconium is preferentially extracted with N235. After washing, atomic-level zirconia containing hafnium <0.01% can be obtained. The hafnium in the raffinate is enriched to 50% to 70%, and then extracted by P204, and the zirconium and hafnium are further separated to obtain atomic energy level hafnium oxide containing more than 96% of hafnium.

This process has low material toxicity, light equipment corrosion, stable operation, and easy disposal of waste, so it is currently recognized as one of the best extraction processes.

Extraction equipment

There are two main types of extraction equipment, one is the extraction tower, and the other is the box-type mixer-settler. The former is used by the MIBK process, and the latter is used by TBP and N235 extraction process. The extraction tower occupies a small area and has a large production capacity. The box-type mixer-clarifier is simple in structure and stable in operation, and is generally made of acid-resistant materials such as plastic or plexiglass.

For more information, please visit https://www.samaterials.com/.

3 Methods to Separate Zirconium & Hafnium

The two elements of zirconium and hafnium are symbiotic resources, which means that zirconium generally contains 0.5% to 2% of hafnium. However, the application of zirconium products in various industries requires high purity. For example, zirconium, which is a structural and cladding material for nuclear reactors, must contain less than 0.01% hafnium. In general, the metallurgical process of separating zirconium and hafnium is an important part of the zirconium metallurgical process.

The separation methods of zirconium and hafnium include pyrolysis separation, solvent extraction separation, and ion exchange separation. This article will briefly introduce these three separation methods.

Zirconium and Hafnium Pyrolysis Separation

Pyro separation is a method of separating zirconium and hafnium at high temperature or high pressure by using the difference in vapor pressure of zirconium and hafnium chloride. Zirconium and hafnium pyrolysis can replace the three production stages of extraction, calcination and chlorination in common separation methods. It has the characteristics of a short production process, high efficiency, low reagent cost and light pollution to the environment, and is a promising method for separating zirconium and hafnium.

The pyrolysis method is mainly realized by high-pressure rectification and molten salt rectification. High-pressure rectification is a process of directly separating zirconium and hafnium by using the difference in vapor pressure of Zrcl4 and HfCl4. Molten salt rectification is a process of separating zirconium and hafnium in a rectifying tower by using the difference in saturated vapor pressure of ZrCl4 and HfCl4 in KAlCl4 molten salt.

3 Methods to Separate Zirconium & Hafnium

Zirconium and Hafnium Solvent Extraction

This is a method for the separation of zirconium and hafnium using solvent leather. Compared with other separation methods of zirconium and hafnium, this method has the advantages of large production capacity, simple process, and easy to achieve continuously. It is the most important method for the separation of zirconium and hafnium.

The reagents used in this method mainly include ketone extractant, neutral phosphorus-containing extractant and amine extractant. There are three extraction processes of MIBK, TBP and N235. There are two main types of extraction equipment, one is the extraction tower, and the other is the box-type mixer-settler. The former is used by the MIBK process, and the latter is used by TBP and N235 extraction process. The extraction tower occupies a small area and has a large production capacity. The box-type mixer-clarifier is simple in structure and stable in operation, and is generally made of acid-resistant materials such as plastic or plexiglass.

Further Reading: Separation of Zirconium and Hafnium by Solvent Extraction

Zirconium and Hafnium Ion Exchange Separation

As the name suggests, this is a method for the separation of zirconium and hafnium by ion exchange. The production volume of this method is small. Only the former Soviet Union has used it to further separate zirconium and hafnium from the hafnium-rich material separated by the zirconium-hafnium recrystallization method to obtain hafnium oxide, which is used as the raw material for the production of atomic-level sponge hafnium.

For more information, please visit https://www.samaterials.com/.

3 Types of Zirconium Based Getter Materials

Zirconium-based getter material refers to the alloy with high absorption active gas characteristics formed by adding other elements based on zirconium.

Before sealing in vacuum tubes and devices, the material must be heated and activated under vacuum conditions for fast and effective gettering. The function of activation is to remove the passivation film formed on the surface during the manufacturing and storage process to expose the fresh surface, which is conducive to the overall gettering, so as to achieve the purpose of absorbing a large amount of oxygen, nitrogen, hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, and water vapor.

Zirconium-aluminum alloy, zirconium-graphite, and zirconium-vanadium-iron alloy are widely used zirconium-based getter materials today.

Zirconium-aluminum alloy getter

Zirconium-aluminum alloy getter can be made into ring-shaped material and composite strip-shaped material.

(1) Ring-shaped material. The material has poor gettering performance at room temperature and is usually not used for gettering at room temperature. This material is commonly used in electronic tubes, various vacuum devices, special lamps, inert gas purification, zirconium-aluminum getter pumps, etc.

(2) Composite strip material. The advantage is that the amount of mercury can be accurately controlled, and it does not decompose or generate mercury vapor below 500°C, thereby greatly reducing environmental pollution, preventing workers from mercury poisoning, and improving lamp quality and life. It has been widely used in fluorescent lamps and energy-saving lamps.

ZR1422 Zirconium Aluminum Alloy, ZrAl Alloy
ZR1422 Zirconium Aluminum Alloy, ZrAl Alloy

Zirconium graphite getter

Zirconium graphite getter is often used in high-reliability and long-life vacuum tubes and devices for long-term operation and storage, such as traveling wave tubes, X-ray tubes, trigger tubes, ceramic tubes, and laser tubes.

Zirconium-vanadium-iron alloy getter

Zirconium-vanadium-iron alloy getter is a low-temperature activated getter material composed of zirconium, vanadium, and a small amount of iron. It is divided into two types:

(1) Zirconium vanadium ferroalloy getter material, smelted by 70%zr+24.6%V+5.4%Fe in electric arc furnace or medium frequency induction furnace under vacuum or filled with inert gas, then crushed, pulverized, and then pressed into getter elements.

(2) (Zirconium vanadium ferro)/zirconium getter material. It is made by adding the zirconium vanadium ferroalloy powder prepared in (1), adding zirconium powder in a certain proportion, mixing evenly, and then pressing, high temperature and high vacuum sintering and other processes. into a suction element. Product forms are powder, flakes, rings, and strips.

These two zirconium-vanadium-iron alloy getters are low-temperature activated getters, and the activation process is as follows: the temperature is 400-600°C, the vacuum degree is 10-2-10-4Pa, and the maintenance is 10-30min. The working temperature is from room temperature to 350℃.

Zirconium-vanadium-iron alloy getter is widely used in stainless steel vacuum insulated cups (bottles), solar vacuum water heaters, high-efficiency oil-insulated pipes, and vacuum tube containers that are only allowed to operate at 500°C.

For more information, please visit https://www.samaterials.com/.

Zirconium – A Vacuum Material

Properties of Zirconium

Zirconium easily absorbs hydrogen, nitrogen, and oxygen; zirconium has a strong affinity for oxygen, and oxygen dissolved in zirconium at 1000°C can significantly increase its volume. The surface of zirconium is easy to form an oxide film with luster, so its appearance is similar to that of steel. Zirconium is resistant to corrosion but is soluble in hydrofluoric acid and aqua regia. At high temperatures, zirconium can react with non-metallic elements and many metal elements to form solid solutions. Zirconium has good plasticity and is easy to be processed into plates, wires, etc. Zirconium can absorb a large amount of oxygen, hydrogen, nitrogen, and other gases when heated, and can be used as a hydrogen storage material. The corrosion resistance of zirconium is better than that of titanium, and it is close to niobium and tantalum. Zirconium and hafnium are two metals with similar chemical properties that are symbiotic together and contain radioactive substances.

Applications of Zirconium

Like lithium and titanium, zirconium can strongly absorb nitrogen, hydrogen, oxygen, and other gases. When the temperature exceeds 900 degrees Celsius, zirconium can absorb nitrogen violently; under the condition of 200 degrees Celsius, 100 grams of metal zirconium can absorb 817 liters of hydrogen, which is equivalent to more than 800,000 times that of iron. This characteristic of zirconium makes it widely used in the electric vacuum industry. People use zirconium powder to coat the surface of the anode and other heated parts of electric vacuum components and instruments to absorb residual gas in vacuum tubes. The high vacuum tubes and other electric vacuum instruments made in this way have high quality and long service life.

high vacuum tubes

Zirconium has a small thermal neutron capture cross-section and has outstanding nuclear properties, so it is an indispensable material for the development of the atomic energy industry and can be used as a reactor core structural material. Zirconium powder is easy to burn in the air and can be used as a detonator and smokeless powder. Zirconium can be used as an additive for deoxidation and desulfurization of high-quality steel and is also a component of armor steel, cannon steel, stainless steel, and heat-resistant steel.

Zirconium can also be used as a “vitamin” in the metallurgical industry to exert its powerful deoxidation, nitrogen removal, and sulfur removal effects. Adding 1/1000 zirconium to steel will increase the hardness and strength amazingly; zirconium-containing armored steel, stainless steel, and heat-resistant steel are important materials for the manufacture of defense weapons such as armored vehicles, tanks, cannons, and bulletproof panels. When zirconium is mixed into copper and drawn into copper wire, the conductivity is not weakened, while the melting point is greatly improved, which is very suitable for high-voltage wires. Zirconium-containing zinc-magnesium alloy is light and resistant to high temperatures, and its strength is twice that of ordinary magnesium alloys. It can be used in the manufacture of jet engine components.

Zirconium powder is characterized by a low ignition point and fast burning speed and can be used as a primer for detonating detonators, which can explode even underwater. Zirconium powder plus oxidant is like adding fuel to the fire, it burns with strong light and dazzling, and it is a good material for making tracer and flare.

Zirconium alloys and their applications

Zirconium alloy is a non-ferrous alloy composed of zirconium as the matrix and other elements are added. The main alloying elements are tin, niobium, iron, and so on. Zirconium alloy has good corrosion resistance, moderate mechanical properties, low atomic thermal neutron absorption cross-section in high temperature and high-pressure water and steam at 300-400 °C, and has good compatibility with nuclear fuel. In addition, zirconium alloy has excellent corrosion resistance to various acids, alkalis, and salts, and has a strong affinity with oxygen, nitrogen, and other gases, so it is also used in the manufacture of corrosion-resistant parts and pharmaceutical machinery parts. For example, it is widely used as a non-evaporable getter in the electric vacuum and light bulb industries.

zirconium alloy

There are two types of zirconium alloys produced on an industrial scale: the zirconium-tin series and the zirconium-niobium series. The former alloy grades are Zr-2 and Zr-4, and the typical representative of the latter is Zr-2.5Nb. In zirconium-tin alloys, the alloying elements tin, iron, chromium, and nickel can improve the strength, corrosion resistance, and thermal conductivity of the corrosion-resistant film, and reduce the sensitivity of the surface state to corrosion. Usually, Zr-2 alloys are used in boiling water reactors, and Zr-4 alloys are used in pressurized water reactors. In zirconium-niobium-based alloys, the corrosion resistance of the alloy is the best when the addition amount of niobium reaches the solid solution limit of the crystal structure of zirconium at the service temperature. Zirconium alloy has isomorphous transformation, the crystal structure is body-centered cubic at high temperature, and hexagonal close-packed at low temperature. Zirconium alloy has good plasticity and can be made into pipes, plates, bars and wires by plastic processing; its weldability is also good and can be used for welding.

Other Zirconium Compounds

Zirconium dioxide and zircon are the most valuable compounds in refractory materials. Zirconium dioxide is the main material of new ceramics and cannot be used as a heating material that resists high-temperature oxidation. Zirconium dioxide can be used as an additive for acid-resistant enamel and glass, which can significantly improve the elasticity, chemical stability, and heat resistance of glass. Zircon has a strong light reflection performance and good thermal stability and can be used as sunscreen in ceramics and glass. Zirconium can absorb a large amount of oxygen, hydrogen, ammonia, and other gases when heated, and is an ideal getter. For example, zirconium powder is used as a degassing agent in electronic tubes, and zirconium wire and zirconium sheets are used as grid supports and anode supports.

Powdered iron mixed with zirconium nitrate can be used as glitter powder. Zirconium metal is used almost exclusively as the cladding for uranium fuel elements in nuclear reactors. It is also used to make photographic flashes, as well as corrosion-resistant containers and pipes, especially hydrochloric and sulfuric acids. Zirconium chemicals can be used as crosslinking agents for polymers.

For more information, please visit https://www.samaterials.com/.

Two Surface Treatment Technologies for Zirconium Materials

The surface of the zirconium rod and zirconium alloy must be clean and smooth before joining, heat treatment, electroplating and forming. This article introduces 2 types of surface treatment methods for zirconium materials.

  1. Surface decontamination

Grease, oil, and lubricants produced during zirconium machining or other processing can be removed in a number of ways. Commonly used cleaning methods are

1) cleaning with alkaline or milky detergent in a soaking tank;

2) cleaning with ultrasonic vibration;

3) rinsing with acetone or trichloroethylene or steam degreasing and

4) cleaning with other cleaning agents.

Small stains can also be removed by hand wiping with some solvents such as acetone, alcohol, trichloroethylene, or a trichloroethylene substitute. In the electrolyte system, if the voltage and current can be controlled to avoid anodic polarization or spark discharge and pitting, positive or negative polarity decontamination can be used. Before heat treatment and bonding, the surface of the zirconium material must be cleaned to prevent metal contamination and the resulting deterioration of ductility.

Surface Treatment Technologies for Zirconium Materials

  1. Blast cleaning

Mechanical decontamination methods such as sandblasting, shot blasting, and evaporative cleaning can remove dirt and lubricants from zirconium and hafnium surfaces. Alumina, silicon carbide, silica and steel grit are ideal media for mechanical decontamination. The decontamination medium used should be replaced regularly to avoid increased workload due to particle passivation.

Grinding or shot peening may cause residual compressive stress and thermal deformation on the surface of the material, especially the surface of the sheet. Hot deformation may also occur during subsequent rolling and profile machining.

Blast cleaning is not a substitute for pickling. Blast cleaning cannot remove surfaces contaminated with interstitial elements such as carbon, oxygen, and nitrogen. In general, blast cleaning followed by pickling can ensure the complete removal of surface contamination and cold-worked layers, resulting in a smooth, shiny metal surface.

For more information, please visit https://www.samaterials.com/.

How to Ensure the Welding Quality of Zirconium Alloy

In the previous article, we introduced the basic properties of zirconium alloys and the problems that easily occur during the welding process. Next, we will explain how to ensure the welding quality of zirconium alloys and some precautions.

Precautions for zirconium alloy welding

  • In the welding prefabrication stage of a large number of welds, a special closed clean place needs to be set up, and strict control of environmental dust pollution and air humidity. For example, when entering the construction site, measures such as wearing clean labor insurance shoes must be worn to ensure the cleanness of the welding environment. In the outdoor installation environment, make a temporary operating room to achieve clean conditions.
  • Strengthening the requirements for the weld joint groove and within 70mm of both sides of the groove and the cleanliness of the surface of the welding wire is an important factor to ensure the welding quality.
  • In the welding process of zirconium alloy, pores are the most prone to defects, and it is mostly concentrated near the fusion line and the centerline of the weld. The most critical steps to prevent the occurrence of welding porosity defects are to strengthen the control of the cleanliness and humidity of the welding environment, and to enhance the cleaning of the bevel and the surface of the welding material, so as to improve the quality of the internal and external protection of high purity argon in the weld zone.
  • The zirconium alloy has a low thermal expansion coefficient, a small amount of thermal deformation, and a small volume change during phase change. It has a low content of impurities such as sulfur, phosphorus, and carbon, so there is no obvious tendency to form cracks during welding. However, when the welding seam absorbs a certain amount of oxygen, nitrogen and hydrogen gas impurities, the performance of the welding seam and the heat-affected zone will become brittle. If there is stress in the weld in the peer group, a cold crack will occur. In addition, the hydrogen atoms have the property of diffusing and accumulating to the high-stress parts in the heat-affected zone at a relatively low temperature, which promotes the formation of relatively weak links in these parts, which may lead to the occurrence of delayed welding cracks.
  • In the welding test, manual tungsten argon arc welding with low welding line energy and convenient gas welding protection should be selected; The larger-diameter welding torch nozzle, the outer surface of the weld seam, and the internal argon filling method of the pipe are used for air isolation to achieve the purpose of the weld seam not being oxidized and absorbing harmful gases.
  • The filler wire used for zirconium alloy welding should be selected according to the principle of matching the composition of the base metal. The surface of the welding wire must be free from defects such as heavy skin, cracks, oxidation, and metal or non-metallic inclusions. The welding wire should be cleaned and dried before use.
  • Zirconium alloy tungsten arc welding requires high-purity argon with a purity of not less than 99.999%, and its impurity content meets the requirements of the current GB / T4842 standard. Due to the extremely high requirements for the purity of the welding protective gas, the welding process needs to be continuously inflated and cannot be interrupted halfway, otherwise, the argon filling must be replaced again. The method of using an ordinary single bottle of argon direct gas supply cannot meet the protection requirements. Multiple bottles of argon gas need to be connected in series to increase the gas supply capacity, and multiple welders can be operated simultaneously by dividing the cylinder.
  • Because zirconium alloys are active at high temperatures, relying solely on the argon gas supplied by the argon arc welding torch nozzle to protect the molten pool and high-temperature bead and heat-affected zone during welding cannot guarantee the welding quality. In order to ensure that the requirements for gas isolation in high-temperature areas and prolonged argon protection time are met, special external gas protection devices for pipes must be added to provide high-purity argon isolation protection for weld pools, high-temperature weld beads and heat-affected zones at high temperatures.

Stanford Advanced Materials supplies high-quality zirconium alloy products to meet our customers’ R&D and production needs. Please visit https://www.samaterials.com/ for more information.