月: 2023年3月

What Is Scalping?

Scalping refers to the process of removing surface defects in machining operations. It is a critical step in ensuring the quality and precision of machined products.

In powder engineering, scalping also denotes the process of removing coarse particles from a bulk of finer particles. This operation typically involves sieving to filter out foreign matter, resulting in a separation of high-grade particles from the beneficiated ore group.

Uses of Scalping

Scalping is commonly used in the manufacturing of sheet metal. Scalping cutters, a specialized tool, are employed to remove oxide layers and contaminants from the surface of sheet metal. This is a vital pretreatment step before forming the metal material into long sheets in rolling processes.

Scalping cutters are designed for surface grinding of various plates, featuring a cylindrical body with cutting edges spaced around its circumference. They work by moving the plate in the axial direction while simultaneously rotating the cutter in the opposite direction, creating a wide and shallow cut on the face of the plate.

Principle of Scalping

Scalping is not limited to flat surfaces; it is also used for cylindrical or tubular materials such as billets. Traditional scalping machines move the billet along an axis and remove its surface layer. These machines typically consist of a loader, which holds and moves the billet, and a cutting blade known as a scupper. Originally, loaders with angled sides were used, but their design has been refined over time to improve efficiency and effectiveness.

In the context of ore dressing, scalping is a sieving process used to separate particles by size. Traditionally, scalping was effective for particles 100 µm or larger. However, technological advancements have improved its precision, allowing for the effective separation of particles as small as 3 µm. In ore dressing, scalping facilitates the sorting and grading of ores by size.

What Is Duralumin?

Duralumin is a type of high-strength aluminum alloy.

The standard composition is aluminum with 4% copper and small amounts of magnesium and manganese. duralumin is heated to about 540°C, quenched in water, and left at room temperature for about 96 hours to gradually harden to a strength comparable to that of mild steel.

Duralumin is an extremely practical alloy because its density is about one-third that of steel while its strength is equivalent to steel.

As aircraft have developed, improvements have been made, and higher-strength super duralumin and extra super duralumin have also been put to practical use.

Uses of Duralumin

Duralumin’s specific gravity is about one-third that of iron, and its strength per unit weight is three times that of iron. For this reason, duralumin is best suited for use in aircraft, which require a high strength value, and has long been used as a structural material for aircraft fuselages.

It is also used as a structural material for automobiles, construction, and other strong structural materials due to its superior properties.

It is also used in industrial applications such as screws, aerospace equipment, gear parts, rivets, hydraulic parts, and marine parts, and is widely used in familiar products such as skis, metal bats, and other sporting goods.

Properties of Duralumin

Duralumin has excellent machinability compared to other aluminum alloys, but its fusion weldability and corrosion resistance are relatively weak. Therefore, when duralumin is used for parts or products to be used in corrosive environments, adequate corrosion protection treatment is required. This drawback is caused by copper added to increase hardness, which reduces corrosion resistance.

Examples of anti-corrosion treatment methods include using duralumin sandwiched between stainless steel or other materials with excellent corrosion resistance.

Types of Duralumin

In addition to ordinary duralumin, there are two other types of duralumin: super duralumin and extra super duralumin.

1. Super Duralumin

Super Duralumin differs from ordinary duralumin in the amount of copper and magnesium added. By increasing the addition of copper and magnesium, it has higher strength and machinability than duralumin. 

2. Extra Super Duralumin

Extra Super Duralumin has much higher strength than duralumin. Duralumin is an alloy of copper and magnesium with additional zinc. The strength of duralumin is only slightly less than that of stainless steel, making it one of the strongest aluminum alloys.

Regarding machinability, duralumin and super duralumin are good and easy to cut, while extra super duralumin is a difficult-to-cut material due to its high strength.

Other Information on Duralumin

1. Strength of Duralumin

Duralumin has a strength of 425N/mm2, which is much higher than aluminum’s tensile strength of 260N/mm2. Duralumin can be said to have a tensile strength equivalent to steel even though it is an aluminum alloy. In addition, its specific gravity is 2.79, much lower than that of steel (7.87), so it has the advantage of being about three times lighter than steel while having the same level of strength.

2. Disadvantages of Duralumin

One drawback of duralumin is its low weldability. Like aluminum, it has high thermal conductivity and is prone to distortion compared to steel, so welding time must be shortened. It is a very difficult material to weld because the melting point is also low and the base metal tends to melt off. For this reason, measures are taken such as using resistance spot welders with lower temperatures than normal welding, and in some cases, rivets and bolts are used instead of welding to join the material.

Among aluminum alloys, duralumin is particularly susceptible to intergranular corrosion, in which corrosion occurs between crystals of the metal, which has the disadvantage of causing cracking.

What Is a Gyrotron?

A gyrotron is a type of vacuum tube device in which electrons orbit around a magnetic field generated by a superconducting coil. These electrons are accelerated by high-speed rotational energy and then converted into high-power millimeter-wave microwaves, which are emitted in a cavity resonator.

The term “gyro” refers to rotation and involves the Cyclotron Resonance Maser (CRM) phenomenon. CRM is a process where the kinetic energy of electrons, rotated by electromagnetic force, is transformed into microwaves.

The millimeter wave band, ranging from 1mm to 10mm in wavelength and 30GHz to 300GHz in frequency, is known for its high linearity and large information-carrying capacity.

Uses of Gyrotrons

Gyrotrons have several applications:

• Industrial Fields: Ceramic sintering.
• Research and Development Fields: Plasma-related processes (heating, measurement, etc.) for fusion experimental devices in laboratories.
• Sub-THz Band: Satellite communications, simple radio, subscriber radio access (38 GHz band), various automotive radars, LiDAR, ADAS, autonomous driving, etc.

Gyrotrons, as high-power radio wave sources in the millimeter wave band, are being increasingly researched for applications in advanced Beyond 5G/6G communications.

Principle of Gyrotrons

Gyrotrons operate on the principle of the cyclotron resonance maser phenomenon. Electrons emitted from an electron gun inside the gyrotron gain spiral kinetic energy as they pass through a superconducting magnetic field. This energy is converted into high-power electromagnetic waves in the millimeter wave band inside a cavity resonator.

Electrons, accelerated by a high voltage (about 100 kV) in an electron gun, obtain high-speed rotational energy when passing through a magnetic field generated by a superconducting magnet (up to 10 T (tesla)). These electrons spiral into a collector in the vacuum tube, which ultimately captures them.

As the spiraling electrons pass through a resonator, they resonate and lose some kinetic energy, which is then converted into electromagnetic waves. These waves are reflected multiple times within the gyrotron and finally emitted through a window, such as an artificial diamond, as high-power millimeter-wave electromagnetic waves.

Other Information on Gyrotrons

1. Development of Nuclear Fusion and Gyrotrons

Nuclear fusion technology is regarded as a promising future power generation method. High-power sub-THz millimeter waves from gyrotrons are transmitted to a fusion reactor, about 100 meters away, to heat the plasma and initiate nuclear fusion.

The International Thermonuclear Experimental Reactor (ITER), a global collaboration project for clean energy generation, is expected to start operation in 2025. Developing gyrotrons for heating and various measurements in fusion facilities is being actively pursued.

2. Gyrotron Frequency

One of the most promising fusion facilities is the Tokamak fusion reactor. The plasma must be heated to ultra-high temperatures in a strong superconducting magnetic field in this reactor. The superconducting magnetic field varies between the center and the edges of the reactor. Therefore, having a gyrotron that can select multiple resonance frequencies is advantageous for maximizing the use of the reactor’s interior.

As per a 2022 announcement by Japan’s National Institute of Quantum Science and Technology, improvements in gyrotron components will enable one megawatt-class operation for 300 seconds at three millimeter-wave frequencies (170 GHz/137 GHz/104 GHz). This advancement is a significant step towards the practical application of nuclear fusion. Furthermore, a breakthrough in increasing the gyrotron’s oscillation frequency to 1013 GHz (THz band) was achieved in 2005 at the University of Fukui’s Center for Far Infrared Research and Development. Joint research for various applications continues both in Japan and internationally.

What Is a Synchrotron?

A synchrotron is an accelerator that controls the high-frequency electric field that accelerates the speed of charged particles and the magnetic field that deflects their path so that they can maintain a constant circumference of their rotation.

While cyclotrons have an ever-increasing radius of gyration, synchrotrons can control the kinetic energy of the charged particles that are ultimately extracted by keeping it constant. This also eliminates the problems associated with the effects of relativity.

Uses of Synchrotrons

Synchrotrons are used in particle beam (heavy particle and proton beam) therapy, a type of radiation therapy currently used in cancer treatment. Radiation therapy has attracted attention because of its various advantages over conventional particle therapy using photon beams, such as X-rays or proton beams.

In particular, heavy particle therapy uses carbon ions, which are even larger particles than protons, and has been confirmed to be effective in treating diseases that have been difficult to treat with conventional radiotherapy.

Other Information on Synchrotrons

Features of Synchrotrons

One of the major applications of synchrotrons is heavy particle radiotherapy, which offers advantages that have not been available in conventional cancer treatment. Currently, there are three types of cancer treatment: surgery, radiation therapy, and chemotherapy.

Radiation therapy, one of the treatments, uses particle beams such as X-rays and protons, and depending on the type of cancer, has a cure rate comparable to that of surgery. On the other hand, localized side effects are said to be unavoidable.

The advantages of heavy particle radiation therapy are that it is effective for cancers deep inside the body and for cancers that are difficult to treat with X-rays or protons.

Heavy particle irradiation from two directions (horizontal and vertical irradiation) makes it possible to concentrate irradiation on cancers deep inside the body, without damaging the surrounding normal cells.

In addition, the irradiation of heavy particles (e.g., carbon ions), which have a relatively large mass, has enhanced the ability to kill cancers such as sarcomas that have not been effectively treated with conventional radiotherapy.

What Is Killed Steel?

Killed steel refers to a type of steel characterized by specific manufacturing processes and properties. It is defined by certain conditions necessary for its categorization as killed steel.

During the steel manufacturing process, iron ore is melted to produce pig iron. Since pig iron contains many impurities, steel is produced through a series of processes, including pig iron making, refining, and steel-making.

In the refining stage, oxygen is removed from the molten steel (deoxidization), particularly towards the end of the process. This deoxidization prevents the generation of gases during cooling and solidification, resulting in higher-quality steel.

Based on the level of deoxidation, three types of raw materials (ingots) are produced. The most deoxidized form is known as killed steel, whereas other types include semi-killed and rimmed steel.

Killed steel typically contains about 50 to 100 parts per million (PPM) of oxygen, compared to 100 to 200 PPM in other steel types.

Uses of Killed Steel

Killed steel is distinguished by its manufacturing process, which involves extensive deoxidation and compositional adjustments. This results in a special steel material with exceptional hardness.

Due to the addition of alloying elements during manufacturing, it is possible to produce steel with desired properties, such as hardness, tenacity, wear resistance, heat resistance, and corrosion resistance.

This makes killed steel suitable for structural steel applications in vehicles, machinery, construction, and shipbuilding, where robustness is essential.

Additionally, tool steel, a variant of killed steel with high hardness, is utilized for cutting tools, molds, bits, drills, and similar applications.

Characteristics of Killed Steel

Killed steel is classified based on the deoxidizing agent used. If silicon (ferrosilicon) is employed, it is termed silicon-killed steel; if aluminum is used, it is known as aluminum-killed steel.

Killed steel serves as a raw material for carbon steel, alloy steel, SS material, etc. Its use varies widely based on its composition.

For example, structural steel, often required for its strength, is utilized in civil engineering, construction, and machinery. Stainless steel, another form of special steel, is commonly used in household items.

Tool steels, necessary for their extreme hardness, are employed in cutting and processing tools, as well as in molds for plastic molding. Superalloys, capable of maintaining high hardness at extreme temperatures, are used in aircraft, gas turbines, and similar high-performance applications.

Other steel types include spring steel for various springs and vehicle plate springs, bearing steel for bearings and rollers requiring wear resistance, and free-cutting steel, which is specialized for ease of machining rather than hardness, ideal for high-precision parts and products.

What Is a Whisker?

Whiskers are fine, whisker-shaped, or needle-shaped single-crystal metal structures that spontaneously grow from the surfaces of metals, commonly tin (Sn) or zinc (Zn) platings. These tiny structures, typically 1-2 microns in diameter and 1-10 microns in length, can cause short circuits in electronic devices by bridging different potential points or by breaking off and infiltrating circuits.

Whiskers were a notable issue in the mid-20th century with the use of zinc and tin in plating and soldering. The shift to lead-free solder since 2000 has seen a resurgence of whisker-related problems in electronic equipment.

Uses of Whiskers

While generally problematic for electrical equipment, whiskers are valued in other applications due to their high strength, heat resistance, and corrosion resistance. They are used as reinforcing materials in ceramics, metals, and plastic composites, particularly in microwave-heatable ceramics and hard ceramics for cutting tools.

Features of Whiskers

Whiskers are categorized into genuine and non-genuine types:

• Genuine Whiskers: These single crystals grow on metal surfaces at room temperature under minor compressive stress. Commonly found on tin, zinc, and cadmium, they can also occur on other metals like silver, gold, iron, and lead under high temperatures.
• Non-Genuine Whiskers: Typically produced artificially and utilized as reinforcing agents in metals and plastics, these whiskers are formed through various processes like vapor phase condensation, electrolytic deposition, and thermal decomposition.

Silicon carbide or silicon nitride whiskers are also used in some applications for reinforcement purposes.

What Is Alumina Fiber?

Alumina Fiber is a fibrous material composed mainly of alumina (aluminum oxide). It is used in various industrial fields because of its high resistance to high temperatures and refractoriness.

Alumina Fiber is made from alumina, which is spun at high temperatures and then calcined at high temperatures to form fibers. Generally, the fiber diameter is a few micrometers, and it is very light, refractory, and strong.

Because it is often used under high temperatures, it has excellent heat resistance and thermal insulation properties. It is also chemically stable and highly resistant to corrosion.

Uses of Alumina Fiber

The main applications of alumina fiber are as follows:

1. Refractory Materials

Examples include glass furnaces, ceramic furnaces, blast furnaces for steel, cement kilns, refractory bricks and refractory cement.

Alumina Fiber is used as a refractory material because of its high temperature resistance and excellent refractoriness. Alumina fiber is also flexible and easy to process, so it can be cut and pasted according to its shape.

2. High-Temperature Insulation Material

Examples include heat treatment furnaces, casting furnaces, paper machines, glass furnaces, heat insulators for molten metal, tanks, and pipelines.

Alumina Fiber has high thermal insulation performance and is used to reduce heat transfer at high temperatures. In addition, it is lightweight and flexible, and can be freely processed to adapt to a variety of shapes.

3. Electrical Insulating Materials

Examples include electric furnaces, transformers, capacitors, fuses, and wires.

Alumina Fiber is used as an electrical insulator because of its high voltage resistance and low conductivity. In addition, it has excellent durability and can withstand long-term use.

4. Reinforcement Material for Mechanical Parts

Examples include aircraft, automobiles, and rolling stock.

Alumina Fiber is used as a reinforcement material for mechanical parts because of its high strength, light weight, and durability. It also has excellent abrasion and corrosion resistance, thus extending the service life of mechanical parts.

Properties of Alumina Fiber

Alumina Fiber has the following properties:

1. Heat Resistance

Alumina has an extremely high melting point of approximately 2,072°C, making it stable under high temperatures. In addition, Alumina Fiber has a dense crystalline structure and the fiber itself is very thin, so the fiber does not deform under high temperatures and retains its strength.

2. Lightweight and Strong

Alumina Fiber is extremely lightweight and strong. Alumina is a very hard material with a dense crystalline structure. It is hard and tough, and the fiber itself is very thin, making it possible to reduce weight.

3. Electrical Insulation Properties

Alumina Fiber is an excellent insulating material and can be made into a fiber and still retain its insulating properties. It is an ionic crystalline material with excellent insulating properties.

An ionic crystalline material is a material with a crystalline structure consisting of a regular arrangement of ions, consisting of cations and anions.

Ions are electrically charged atoms or molecules; cations have a positive electrical charge and anions have a negative electrical charge. Ion-crystalline materials are usually composed of metal and non-metal ions.

Ion-crystalline materials have high crystallinity and strong bonding forces, resulting in properties such as high hardness and melting point, electrical insulation, and thermal conductivity. They are also chemically stable and resistant to acids and alkalis.

4. Corrosion Resistance

Alumina is a very chemically stable material and has excellent corrosion resistance. Alumina fiber likewise has excellent resistance to oxidation and corrosion.

The chemical stability of alumina is due to its crystal structure. Alumina is a compound of aluminum and oxygen, and its crystal structure belongs to the triclinic system. The tricrystalline structure is very rigid and is characterized by a high resistance to chemical attack.

In addition, alumina has a very high melting point and is chemically stable at high temperatures, thus maintaining corrosion resistance even in high temperature environments.

5. Wear Resistance

The tricrystalline crystal structure of alumina is one of the most densely packed structures, so the bonds between atoms are very strong and alumina is a hard material. Therefore, alumina is highly resistant to mechanical loading.

In addition, because alumina has a very dense crystalline structure, there are few micro defects on its surface, making it highly resistant to friction and abrasion. Therefore, alumina fiber is characterized by its high resistance to friction and abrasion between fibers.

Other Information on Alumina Fiber

Processability of Alumina

Alumina Fiber is very hard and its diameter is extremely fine, making it difficult to cut and process. Special techniques and equipment are required to process alumina fibers because cutting shortens the fibers. Also, because the fibers are very fine, care must be taken when handling them. The fibers may scatter when processed.

Alumina Fiber tends to become brittle when exposed to high temperatures for long periods of time. The reason is that the fiber oxidizes in a high-temperature environment, resulting in an increase in fine crystal particles, which makes the fiber brittle. Therefore, care must be taken when using alumina fiber depending on the environment in which it is used. For example, the fiber should not be exposed to high temperatures for long periods of time, a coating should be applied to protect the fiber, and regular inspection and maintenance should be performed.

What Is an Amorphous Metal?

Amorphous metals are metals with an amorphous structure.

Amorphous metals are subjected to rapid cooling, resulting in an amorphous structure in which the atoms are randomly arranged without crystallization. Because it is amorphous and free of defects caused by grain boundaries, it has a higher strength and is therefore very strong. It also has very elastic and deformation-resistant properties and has high electrical and thermal conductivity.

Applications of Amorphous Metals

1. Automotive Industry

Examples include automotive silencers and weatherproofing of chimneys.

Automotive silencers are part of an automobile’s exhaust system, a device used to reduce the noise of exhaust gases emitted from the engine. Weatherproofing of chimneys is a treatment to prevent corrosion and deterioration that occurs when chimneys are exposed to the external environment.

2. Electronics Industry

Examples include magnetic sensors, solar cells, electronic circuits, and memory.

Magnetic sensors are a type of sensor that detects magnetic fields and converts the information into electrical signals. Solar cells are devices that receive sunlight and convert its light energy into electrical energy. Solar cells generate direct current electricity in response to the intensity of sunlight.

3. Power and Energy Industry

Examples include the iron cores of column transformers, industrial transformers, and small- and medium-sized motors. A column transformer is a type of transformer used to convert high-voltage power from transmission lines into low-voltage power.

4. Machinery Industry

This includes bearings, gears, shafts, nozzles, etc.

5. Magnetic Device Industry

Magnetic head elements and magnetic heads for HDDs are examples. Magnetic head elements are components that contact the surface of magnetic media (e.g., hard disks) to read magnetic information and are usually made in very small sizes.

6. Chemical and Medical Industries

Catalytic materials, taking advantage of their catalytic properties, electromagnets, MRI magnets, etc., take advantage of their superconductivity.

Properties of Amorphous Metals

Amorphous metals do not have the crystalline structure of normal metals, but have an amorphous structure with an irregular arrangement of atoms. For this reason, they have different physical properties compared to crystalline metals. It has extremely high strength and hardness. It is a material that is approximately twice as strong and three times harder than ordinary metals. It also has excellent corrosion resistance, and an oxide film can be formed on the metallic glass surface to improve the corrosion resistance of the metal surface.

Amorphous metals are soft magnetic materials with excellent magnetic properties (excellent magnetic response to magnetic fields) because they do not have the anisotropy of crystalline metals. Their amorphous structure and high thermoplasticity enable the manufacture of parts and products with complex geometries.

Amorphous metals with catalytic properties are used in fuel cells and as catalysts for chemical reactions, while those with hydrogen storage capabilities are used to store and transport hydrogen energy.

Normal metals have a regular lattice structure, and when deformed, crystal grains move among each other, causing deformation. Amorphous metals, however, do not have a crystal structure and there is no movement of crystal grains during deformation, so they easily retain their strength due to intermolecular bonding forces. Since the intermolecular distance is very short and the modulus of elasticity is high, amorphous metals retain their strength even after deformation, and their high resistance to brittle fracture allows them to retain their strength even after repeated deformation.

Amorphous metals have randomly arranged atoms and no grain boundaries or lattice defects, so the flow of free electrons is not restricted. Therefore, they have very low electrical resistance and high conductivity. Amorphous metals also have a high thermal conductivity due to their amorphous structure, making them suitable for use in high-temperature environments.

Other Information on Amorphous Metals

1. Use as Superconductive Materials

Some amorphous metals are also used as superconducting materials. Superconductivity is a phenomenon in which electrical resistance completely disappears when an electric current is passed below a certain temperature. Some amorphous metals exhibit this phenomenon.

2. Use as Glass Metal

Amorphous metals are a type of metallic glass with an amorphous structure. Unlike ordinary glass, metallic glass has a very low coefficient of thermal expansion, which makes it highly durable and resistant to thermal shock.

What Is Phosphor Deoxidized Copper?

Phosphor deoxidized copper is a high-purity copper (99.9% Cu) with a small addition of phosphorus (0.015% to 0.040%). It differs from tough-pitch copper and oxygen-free copper due to this phosphorus content, which acts as a deoxidizer during its production.

The production process involves three stages: obtaining electrolytic copper from crude copper through electrolytic refining, an oxidation process to remove impurities and the addition of phosphorus.

Uses of Phosphor Deoxidized Copper

Known for its high thermal conductivity, phosphor deoxidized copper also boasts excellent drawability, weldability, and corrosion resistance, making it versatile in various applications. It is commonly used in the chemical industry, water heaters, air conditioning piping, construction materials, electric refrigerators, and as welding rods in copper welding.

Characteristics of Phosphor Deoxidized Copper

The key characteristic of phosphor deoxidized copper is its phosphorus content, which removes oxygen from the copper, preventing the formation of water vapor at high temperatures. However, this residual phosphorus also reduces its electrical conductivity to about 85% of that of tough-pitch copper. Therefore, it’s crucial to select applications that align with the specific characteristics of phosphor deoxidized copper.