月: 2023年3月

What Is a Superconducting Motor?

Superconducting motors utilize the phenomenon of superconductivity, where electrical resistance drops to zero at very low temperatures. This allows for the flow of large currents at low voltage, creating strong magnetic fields and enabling motors with excellent torque characteristics.

However, exceeding a critical magnetic field can disrupt the superconducting state of the superconducting wire, reverting it to normal conductivity with standard electrical resistance. Thus, careful management of superconducting magnetic fields is crucial.

Uses of Superconducting Motors

Superconducting motors are expected to be smaller and lighter than traditional electric motors with equivalent output. They are anticipated for use in applications like superconducting linear railroads (linear motor cars), propulsion engines for ships and aircraft, and more.

Examples of practical applications include the Shanghai Maglev Train and Japan’s JR Tokai superconducting linear motor car, slated to open in 2027. Additionally, superconductivity is already employed in medical MRI equipment.

Principle of Superconducting Motors

Superconducting motors use coils made of superconducting wires in the motor rotor, achieving low-loss, high-efficiency operation with excellent torque. Magnets leveraging superconductivity create powerful magnetic fields for linear motor cars, reducing resistance components like wheel friction and enabling ultra-high-speed operation.

Niobium-titanium alloy (Nb-Ti) magnets exhibit superconductivity at the low temperature of 4K (-516°F) in liquid helium. Recent advancements include bismuth-based copper oxide, a high-temperature superconducting magnet that achieves superconductivity at 77K (-516°F) with liquid nitrogen, offering lower costs and easier handling than liquid helium.

Despite ongoing research and development, there are still challenges to overcome before widespread practical application, with major companies in the heavy industry sector actively involved in this work.

What Is a Superconducting Wire?

A superconducting wire is a cable that transmits electric power using a conductor that exhibits no electrical resistance.

While technically feasible, its commercialization faces challenges, including the development of cooling system technologies and the establishment of reliable cable-to-cable connections.

Despite having no electrical resistance theoretically and thus no power transmission loss, practical use reveals minimal losses during high-current AC power transmission, albeit significantly lower than those of conventional cables.

Uses of Superconducting Wires

Utilizing superconducting technology, superconducting wires are employed in electric power transmission. They allow for the transmission of large power loads without heat generation or voltage drop, thanks to their lack of electrical resistance. However, AC loss, a minor yet present loss, does occur.

In AC power transmission, superconducting wires can reduce transmission losses by approximately 95% compared to traditional copper cables.

Principle of Superconducting Wires

With zero resistance, superconducting wires enable significantly smaller power transmission cables, potentially downsizing the extensive infrastructure of power transmission. They facilitate long-distance power transmission without voltage drops, allowing for lower voltage use. Direct current (DC) power transmission, though still experimental, is being explored globally.

Types of Superconducting Wires

Yttrium-based superconducting wires, operable with liquid nitrogen, are known for their high critical currents and favorable magnetic field properties. They promise reduced power transmission losses to about a quarter of those with conventional cables and are suitable for compact, lightweight, and high-capacity applications.

How to Select a Superconducting Wire

Superconducting wires offer low-loss power transmission but face challenges, particularly in AC power transmission where cable losses vary with the power amount. The critical temperature for superconductivity, now at -196°C, necessitates advanced cooling system technologies. For natural energy sources that generate DC power, using superconducting wires can halve the transmission loss compared to AC transmission.

Structure of Superconducting Wires

High-temperature superconducting wire cables comprise a superconducting conductor layer of spirally wound wire tapes around a central former, which adds mechanical strength and acts as a bypass in accidents. An electrical insulating material encases this layer, topped by a superconducting shield layer that blocks magnetic fields from the conductor layer without external leakage. A protective copper wire layer and an insulating double-tube structure, maintaining a vacuum to prevent external heat ingress, enclose the assembly.

What Is Superfluid Helium?

Superfluid helium is formed when helium is cooled below its cryogenic temperature of 2.17 K, transitioning into a viscosity-free liquid state.

As helium’s temperature decreases, it first changes from gas to liquid. Further cooling leads to a secondary phase transition at the λ-point, resulting in superfluid helium.

This state is characterized by extremely weak interatomic forces, allowing helium atoms to penetrate tiny spaces and exhibit unique phenomena due to the absence of viscosity.

Both helium 3 and helium 4 can achieve superfluidity, although their respective λ-points differ.

Uses of Superfluid Helium

Superfluid helium, an excellent conductor of heat, is used primarily for cooling. Its theoretical infinite thermal conductivity makes it an ideal cooling medium.

In practice, superfluid helium is often used in place of liquid helium due to the high costs associated with maintaining its superfluid state.

One significant application is in cooling superconducting helical coils in MRI machines, where it generates stronger magnetic fields than liquid helium, thereby enhancing measurement precision.

It is also crucial in equipment used for measuring minute signals, where even minimal heat generation can impact accuracy, necessitating efficient cooling with superfluid helium.

Characteristics of Superfluid Helium

In its superfluid state, helium exhibits zero friction between atoms, leading to the absence of viscosity.

This lack of interaction between atoms allows them to move freely and penetrate narrow spaces. Consequently, superfluid helium can creep up container walls and spill over (superfluid phenomenon).

Just as an electric current in a superconductor can flow indefinitely once initiated, superfluid helium can flow endlessly once set in motion. Similarly, if rotated at high speed, it continues to rotate indefinitely.

Due to its non-viscous nature, it also flows at a constant rate in thin pipes regardless of pressure and does not achieve thermal equilibrium, allowing for highly efficient cooling systems via superheat conduction.

Maintaining cryogenic temperatures is crucial for retaining superfluid helium’s properties, which are lost if the temperature rises above its λ-point, posing a challenge in its application.

Currently, superfluid helium is mainly used for cooling, with ongoing research into harnessing its unique properties for other technologies.

What Is a Magnetic Wall?

Ordinary magnets are composed of ferromagnetic materials, with ferromagnetism referring to the property of an object being attracted to a magnet.

Ferromagnetic materials consist of atomic layers of magnets, each possessing a vector quantity known as a magnetic moment, which indicates the strength of the magnetic force.

Aligned regions of the magnetic moment are termed magnetic domains. The boundary layer between magnetic domains in different directions is known as the magnetic wall.

Uses of Magnetic Walls

Magnetic domains and walls are crucial in analyzing the behavior of ferromagnetic and ferrimagnetic materials and for practical applications.

Common uses include the magnetic strip on the back of a credit card, PC hard disks, and the backs of train or bus tickets and commuter passes. These are coated with ferromagnetic material, recording information on the magnetic walls (magnetic domains) as artificial digital data of 0s and 1s, facilitating data exchange between these media and integrated systems.

Principle of Magnetic Walls

A simple example to understand the principle of magnetic walls involves metal needles and clips.

A new metal needle or clip, initially non-magnetic, can exhibit magnetic properties when rubbed with a magnet, attracting each other.

This is due to the change in the distribution of magnetic domains and walls within the needle or clip upon contact with a magnet. Rubbing alters these domains, leading to a state where magnetic poles remain on the needle or clip’s surface, effectively turning them into magnets.

Items like credit cards with magnetic strips should be kept away from magnets to avoid irreversible changes to the magnetic domains and walls.

The concept of magnetic walls is also essential in analyzing new ferromagnetic materials and products, such as ferrites.

What Is a Hard Steel Wire?

A hard steel wire is usually made by heat-treating a steel wire rod and then cold-working it, such as drawing.

The term “hard steel” is used to classify steels based on their hardness.

Although often compared to piano wire, piano wire is a high-grade material with strict standards and superior strength, while hard steel wire is a relatively inexpensive general material that is often used in everyday products. Examples of applications include springs for furniture such as chairs and beds, as well as springs for toys, shutters, and bicycles.

Uses of Hard Steel Wires

Hard steel wires are mainly used as springs, needles, and spokes. For example, springs for safety pins, switches, scales, bicycle saddles, etc.

In addition, hard steel wires are used in familiar everyday items such as reinforcements for high-pressure rubber hoses, screwdriver materials, hairpins, etc. In the construction industry, it is also used as shutter springs. In the automotive industry, they are used as seat springs, and in the electronics field, they are used in a wide range of industries as reinforcement for communication lines and power transmission lines.

Types of Hard Steel Wires

There are 21 types of hard steel wire rods used to make hard steel wires, depending on the amount of carbon they contain and their composition. However, hard steel wires made from these wire rods are classified into three types: Type A (SW-A), Type B (SW-B), and Type C (SW-C), with tensile strength increasing in the order of A < B < C. Each type is explained below.

• Hard Steel Wire Type A (SW-A)
  This type has the lowest tensile strength among hard steel wires and is rarely used for springs.
• Hard Steel Wire Type B (SW-B)
  Tensile strength is higher than that of Type A. 60 carbon is widely used as wire material. It is mainly used for springs under static load.
• Hard Steel Wire Type C (SW-C)
  Tensile strength is even higher than that of Type B, and 80 carbon is used as wire material. Like SW-B, it is mainly used for springs under static load.

What Is Gun Metal?

Gun metal is a bronze alloy primarily composed of approximately 90% copper and 10% tin. It is classified as bronze due to its copper-tin composition.

Historically, gun metal was utilized for making cannon barrels, earning its name from this application. It is known for its high toughness and has other notable properties such as wear resistance, castability, corrosion resistance, and strong resistance to seawater, making it suitable for bearing applications.

There are various types of gun metal bronze, including alloys like CA401 and CA402, each offering distinct characteristics and applications.

Uses of Gun Metal

Gun metal’s excellent mechanical properties, corrosion resistance, and wear resistance make it suitable for various applications. These include valves, cocks, water pourers, bearings, gears, impellers, bushings, liquid oxygen manufacturing parts, pump casings, piston rings, water heater components, meter parts, rolling mill worm wheels, marine propellers, paper manufacturing rolls, art castings, landscape castings, plain bearings, electrical equipment parts, general machinery parts, highly elastic spring materials, ship round windows, ship parts, printing parts, chemical industry supplies, toothed washers, signs, bolts, and spring washers.

Characteristics of Gun Metal Alloys

Among the bronze alloys similar to gun metal, five notable compositions include CA401 and CA402:

• “CA401” is a copper alloy in the bronze family known as “valve metal,” used for its excellent flowability and machinability, primarily in valves.
• “CA402” offers superior pressure resistance, wear resistance, and corrosion resistance among bronze castings. It is particularly resistant to seawater, making it ideal for seawater-exposed pump parts.
• “CA403” excels in pressure resistance, wear resistance, and mechanical properties. It is highly resistant to seawater and suitable for abrasive and corrosive environments.
• “CA406,” or “ounce metal”/”leaded-red brass,” is known for its pressure resistance, wear resistance, machinability, and castability. It is one of the most commonly used copper castings.
• “CA407,” superior to “CA406,” is also known as “valve bronze for steam” and is considered for applications requiring even higher properties.

What Are Polishing Patterns?

Polishing patterns are distinctive surface textures achieved through various polishing techniques. These patterns range from stripes created by brushes or abrasives to more intricate designs. The appearance of the polished surface varies with the method used.

Glossy polishing employs buffing pads, resulting in finishes from coarse luster to mirror-like surfaces without visible polishing marks. Satin polishing, a type of vibration polishing, produces a surface with a random pattern of small arcs, often appearing as straight-line hairline patterns.

Scale polishing is characterized by a spun-polished pattern with a scaly appearance.

Uses of Polishing Patterns

For stainless steel, coarse-grain polished finishes are used in building materials and kitchen utensils, while finer, lustrous finishes find applications in vehicles, medical equipment, and food-related equipment. Mirror finishes with subtle striping are also popular for building materials and kitchen utensils. Hairline and vibratory grinding patterns are commonly used in building materials.

Buffing is utilized to minimize surface irregularities and remove dirt, enhancing appearance and aesthetics. It also helps prevent rust and dirt adhesion.

Polishing extends beyond metals to jewelry, marble, optical and electronic components, and even dental and biological substitutes.

Principle of Polishing Patterns

In precision machining, polishing with abrasive grains is prevalent. There are two main types: fixed abrasive, where grains are bonded into a wheel-like shape, and loose abrasive, involving discrete grains.

Fixed abrasive methods include honing and abrasive cloth processing while lapping and polishing are typical loose abrasive methods, each producing unique polished surfaces.

Two categories of abrasive grains are used: natural and artificial. For rough polishing, hard grains like alumina, silicon carbide, and diamond (Mohs hardness 9 or higher) are preferred. Softer, finer grains (Mohs hardness 7 or less) are chosen for fine polishing and finishing.

Lapping involves embedding hard abrasive grains into both the workpiece and the lapping tool, making each grain tip act as a microtool. Polishing is achieved by pouring fine abrasive grains onto a polisher plate and pressing the workpiece against it in relative motion.

Various abrasives, such as belt, film, and wheel types, are available in different coarseness levels. Precision grinding wheels for electronic components are used in lapping and edge grinding of semiconductor wafers and precision grinding of optical glass. Compounds, specifically designed for automotive repair, are also used as abrasives.

What Is Cupronickel?

Cupronickel is a copper-based alloy containing nickel and other metals. It is used in a wide variety of applications because of its excellent properties such as corrosion resistance, workability, strength, hardness, castability, and beautiful color. It is also known as copper-nickel.

Because of its good electrical conductivity and corrosion resistance, it is used for electrical wiring. It is also used for musical instruments due to its good castability, and is widely used especially for brass instruments. Its beautiful color and high corrosion resistance also make it suitable for manufacturing coins and medals.

Uses of Cupronickel

1. Electrical and Electronic Components

Wiring, connectors, circuit boards, electrical resistors, coils, transformers, etc.

2. Electric Circuits

High-frequency circuits, RFID antennas, etc.

RFID antennas are antennas used in RFID (Radio Frequency Identification) technology to transmit and receive information at radio frequencies.

3. Automobiles

Radiators, clutch components (e.g., clutch discs), battery terminals, etc.

A clutch disc is part of the clutch mechanism that connects the engine and transmission (the mechanism used to transfer engine power to the wheels) in vehicles such as cars and motorcycles.

4. Architecture

Roofs, exterior walls, door knobs, and metal fences.

5. Heat Exchanger

Steam turbines, air conditioning units, and freezers. 

6. Medical Equipment

Surgical instruments, artificial joints, dental tools, etc.

7. Metal Parts

Screws, washers, springs, gears, shafts, etc.

8. Decoration

Clocks, light fixtures, metal ornaments, etc.

9. Sporting Goods

Golf clubs, tennis rackets, motorcycle frames, etc.

Types of Cupronickel

There are two types of Cupronickel, C7060 and C7150.

Properties of Cupronickel

1. Color

Cupronickel is an alloy of copper and zinc. Since copper and zinc are both metals, cupronickel is a material with metallic luster. Cupronickel has a beautiful white color because zinc can be added to whiten the color of copper, which has a reddish color in its pure state. Since the surface is not easily oxidized, the luster can be maintained for a long period of time. 

2. Workability

Cupronickel has good workability. As an alloy of copper and zinc, it is soft and easy to work. It also has a uniform microstructure that evenly distributes stress generated during machining and improves workability.

Furthermore, its relatively low melting point and boiling point allow it to be easily heated and reshaped, making it suitable for use in a variety of processing methods, including casting, forging, machining, and cutting.

3. Corrosion Resistance

Cupronickel has excellent corrosion resistance. The reason is due to the following factors.

First, when zinc is oxidized, it forms an oxide film, which enhances the protective action of copper against corrosion. In addition, zinc acts as a cathode in cupronickel alloys, preventing oxidation reactions and providing electrochemical protection.

Finally, its excellent corrosion resistance is also due to its high stability in water and its resistance to corrosion in seawater and fresh water.

4. Thermal Conductivity

Cupronickel is a metal that generally has high thermal conductivity, which allows it to transfer heat efficiently. It also contains zinc, which is a higher thermal conductor than copper, so the overall thermal conductivity is higher when cupronickel contains zinc.

The crystalline structure of cupronickel is characterized by a random arrangement of densely arranged spherical particles, which makes it a good heat conductor. These factors combine to give cupronickel excellent thermal conductivity.

5. Electrical Conductivity

As a metal, cupronickel generally has high electrical conductivity, which allows it to transfer electricity efficiently. In addition, the zinc in cupronickel has a higher electrical conductivity than copper, which helps to increase the overall electrical conductivity.

Furthermore, cupronickel has a densely packed crystal structure, which allows electrons to move freely, resulting in higher electrical conductivity.

6. Strength, Wear Resistance

Cupronickel, an alloy of copper and zinc, has a good balance of hardness and flexibility, and has high strength and excellent wear resistance. It also has a uniform microstructure, with fine crystal particles randomly arranged. Therefore, it distributes stress evenly and improves strength, while at the same time picking up fine crystal particles wear substances.

Specifically, when wear materials created by friction adhere to the surface of cupronickel, the crystalline particles encapsulate the wear materials and prevent their progression. The fine crystalline particles pick up the wear material, making cupronickel highly resistant to wear.

Cupronickel has a smooth surface and generates less heat due to friction, resulting in higher wear resistance.

Other Information on Cupronickel

Magnetism of Cupronickel

Copper is weakly paramagnetic under normal temperature and pressure, and zinc is also weakly paramagnetic under normal temperature and pressure, but cupronickel, an alloy of the two, is a non-magnetic material.

This is closely related to cupronickel’s high electrical conductivity. When a metal is exposed to electromagnetic waves, a magnetic field is generated, and this magnetic field can generate an electric current inside the metal (electromagnetic interference), which can be a problem in high-frequency circuits, for example.

Cupronickel, however, does not generate a magnetic field and does not cause electromagnetic interference, making it suitable for use in electric circuit components such as high-frequency circuits.

What Is Deformed Wire?

Deformed wire is a versatile medium-sized wire, processed into various cross-sectional shapes beyond the standard round, hexagonal, square, and rectangular forms.

Offering significant cost savings over traditional cutting, grinding, and sheet metal processing, deformed wire can be manufactured through cold drawing or cold rolling. Its benefits include weight reduction, yield improvement, process simplification, enhanced accuracy, and a smoother metal surface.

Deformed wire springs exhibit superior spring properties when their cross-section is altered. Through quenching and tempering, they gain excellent straightness, an expanded elastic limit, and a high yield point, leading to enhanced durability. Deformed wire materials encompass a range of options, including carbon steel, alloy steel, stainless steel, copper and copper alloys, and titanium and titanium alloys.

Uses of Deformed Wire

Deformed wire finds application across a broad spectrum, from mechanical components like split pins and springs to ski edges, necklaces, electric heating wires for carpets, wristwatch bands, eyeglass frames, guitar fret wires, and model rails. Additionally, it plays a crucial role in automotive piston ring and transmission parts, various industrial machinery, and the oil, gas, mining, water, paper, and pulp industries, as well as wire rope for forestry and cranes.

Deformed wire is utilized in home appliances, office automation equipment, automobile clutches, brakes, wiper arms, cigarette lighters, and bicycle brakes, typically as springs. A deformed cross-sectional shape can achieve a higher load capacity and longer service life compared to traditional round springs, allowing for more compact and lightweight designs with the same torque.

Principle of Deformed Wire

Deformed wires, with their varied cross sections, are produced by cold drawing or cold rolling coils, typically of circular cross-section materials. The material undergoes surface treatment, stretching through a die, re-coiling, and, if necessary, annealing. Specifically for spring materials, deformed wires are quenched and tempered.

For instance, the durability of a torsion spring made from circular wire can be about twice that of a deformed wire with the same outside diameter and coil number. Similarly, with equal coil turns and free length, the durability can increase sixfold.

Various surface treatments, such as zinc or zinc-aluminum alloy coating, enhance corrosion resistance and aesthetic appeal. Resin coatings for color identification and coloration of stainless steel are also common.

Types of Deformed Wire

Deformed wire is available in an array of materials, including iron wire, steel wire, piano wire, stainless steel wire, aluminum wire, phosphor bronze wire, brass wire, copper wire, special steel, and nickel silver. Iron wire categories include annealed, carbon steel for cold heading, galvanized, and zinc-aluminum plated.

The hardness levels range from HRC40-50 for piano wire, HRC35-45 for hard steel wire, HRC45-52 for oil tempered wire, HRC95-105 for dull wire, to HRC35-45 for stainless steel wire.

Deformed wire packaging options include coils, reel-less coils, carriers, and reels. The cross-sectional shapes encompass flat, square, half-round, trapezoidal, triangular, pentagonal, hexagonal, oval, diamond-shaped, tapered, talc-shaped, convex-shaped, spectacle, half-round spectacle, and round buckled trapezoidal wires.

How to Select Deformed Wire

Deformed wire, with its unique functionality, facilitates achieving a product state close to the final desired outcome, simplifying manufacturing processes by negating the need for additional surface processing and reducing costs.

Modifying the properties of each base material type ensures suitability for specific applications. In low-carbon steels, hardened rolling and tempering aid forming and post-processing. For high-carbon and alloy steels, oil tempering and induction hardening homogenize the steel microstructure, improving tensile strength and fatigue properties. Stainless steels benefit from hardened rolling and tempering as well.

What Is a Sintering Aid?

A sintering aid is an additive used to enhance and stabilize the sintering process of metal and ceramic powders. These aids usually have a lower melting point than the primary material being sintered.

Sintering aids are carefully added to the powders in amounts that don’t compromise the material’s properties. They are particularly useful for sintering materials that are otherwise difficult to sinter or to improve density and strength post-sintering. Commonly used sintering aids include boron, carbon, alkaline earth metals, and rare earth oxides, which are particularly effective for ceramic sintering, enhancing densification and thermal conductivity.

Uses of Sintering Aids

Sintering aids are extensively used in the production of ceramics. Metals with high melting points and ceramics that are unfeasible to produce by conventional methods like cutting or melting are manufactured through sintering. For materials like silicon carbide and silicon nitride, which are challenging to sinter, sintering aids help facilitate densification. They melt at lower temperatures during the heating process, aiding the compacting of the powder.

In the case of fine ceramics, which are even more challenging to sinter, smaller particle sizes and additives like boron and carbon are used. Silicon beryllium nitride is sometimes employed as a sintering aid in silicon nitride ceramics production. Additionally, some ceramic household items are made by mixing ceramic clay with sintering aids and sintering them in a microwave oven.

Principle of Sintering Aids

In the sintering process, raw materials are first pulverized and mixed, with sintering aids added at this stage if needed. The powder is then placed in a mold and pressurized to form the desired shape. Wax or similar materials may be added for easier molding. To ensure even density, particularly with fine powders, a molding aid might be used to create granular material for molding.

Before high-temperature sintering, any organic matter added during molding is slowly heated and removed. For oxide ceramics like alumina and zirconia, most sintering occurs in air, while metals and non-oxide ceramics like silicon nitride are sintered in inert gas or vacuum environments to prevent oxidation.

Sintering involves heating the powder compact, causing raw material particles to bond, reducing voids, and solidifying the structure. Diffusion is a key mechanism in this process, especially for solid metals and ceramics. Materials like SiC and Si3N4 require sintering aids for efficient densification, as high grain boundary energy can hinder sintering. Sintering aids reduce this intergranular energy, enhancing the process. Additionally, low-temperature sintering is crucial for high-temperature structural ceramics to prevent strength loss due to particle growth at high temperatures.