Nickel Metal

Chapter 1: Principle of Nickel Metal

This chapter will discuss what nickel metal is, its production, and how it functions.

What is Nickel Metal?

Metals are a group of substances that are malleable, ductile, and have high heat and electrical conductivity. They can be grouped into five categories with nickel falling in the category known as transition metals. Nickel is a naturally occurring metallic element that is shiny and silvery-white with a gold tinge. Its atomic weight is 58.71, its atomic number is 28, a symbol Ni, and five stable isotopes. It is solid at room temperature, has a boiling point of 2730°C and a melting point of 1455°C. It‘s ferromagnetic, hard, corrosion and rust resistant, and ductile. Since nickel occurs naturally it has to be mined from the earth.

The metal is obtained through a process called extractive metallurgy. Extractive metallurgy is removing a desired metal from its ore and refining it in order to make the extracted metal purer. An ore is a naturally occurring rock, deep in the earth‘s surface that contains one or more valuable minerals that can be mined, refined, and sold for profit. Ore usually contains metals. Nickel has two main types of ore namely: laterites and magmatic sulfide.

Production Process for Nickel

As stated above Nickel has two main types of ore deposits: laterites which are composed mainly of nickeliferous limonite and garnierite, and magmatic sulfide deposits of which the main ore mineral is pentlandite.

Extraction and Processing of Nickel

Extractive metallurgy is the process used to extract the raw metal from its ore. The most common way the metal is extracted is through pyrometallurgical extraction, which involves application of high temperatures to allow chemical reactions to take place. The laterite ore is usually obtained via open cut mining methods. Open cut mining is a form of surface mining where the ore is extracted from an open-air pit whereas the sulfide ore, which is usually found combined with copper, is mined underground. Equipment used for laterite ore mining include big shovels, draglines, and front-end loaders.

Nickel Extraction From Sulfide Ores

After mining the sulfide ores, they are crushed and ground to separate the nickel from the waste materials by a process called selective floatation. During this process the ore is mixed with reagents and then agitated using mechanical and pneumatic devices that produce air bubbles. Sulfide particles, since they are light by nature, adhere to the surfaces of the air bubbles as they rise through the mixture.

They are collected and contain six to twelve percent of nickel. Due to the magnetic nature of some of the nickel containing sulfides magnetic separators are used as well. Sometimes they are used in place of flotation and at times in combination with flotation. The waste materials often undergo a second cleaning step before being thrown away. Some sulfide ores contain nearly equal amounts of copper and nickel as a result a second selective flotation process has to be done resulting in a low nickel copper concentrate and a separate nickel concentrate.

Nickel concentrates are sometimes leached with sulfuric acid or ammonia. At times they may be dried and then smelted in flash processes. Current methods are primarily flash and electric smelting. These methods involve placing the ore in a furnace that has preheated oxygen, this will cause the iron and sulfide to oxide resulting in 25 to 45 percent nickel.

This nickel-iron sulfide is known as matte. In the final stage oxygen is injected into the molten bath. This is done to eliminate any remaining traces of iron and sulfide. The iron combines with the oxygen to form an oxide. This oxide combines with silica flux to form a slag which is removed resulting in a nickel matte of about 70 to 75 percent nickel.

This entire process is done in a rotating converter. Some of the heat required for the smelting process of sulfide ores comes from the reaction of oxygen with iron and sulfur in the ore.

Nickel Extraction From Laterite Ores

Nickel from laterite ores does not contain any sulfur. However they have large amounts of water as moisture and also in the form of hydroxides. Since lateritic ores cannot produce the same reaction temperatures as those of sulfide ores, energy from other sources is used for the drying and smelting process. The drying process is done in order to remove moisture from the ore. The process is carried out in a large-kiln furnace.

The nickel oxide obtained from the process stated above is reduced in order to obtain the nickel metal. Electric furnaces that have a rating of 45 to 50 megavolt-amperes are usually used for the smelting process. The operating temperature of these furnaces is 1360°C to 1610°C.

Refinement of Nickel

After mining nickel ore and the processing described above there remains a substance called nickel matte which usually contains 75 percent nickel. Carrying out further refinement processes can result in a purity as high as 95%. Ammonia pressure leech is a process whereby nickel is obtained from a solution using hydrogen reduction. This process is used to refine nickel obtained from sulfide ores. The sulfur in the ore forms ammonium sulfate, which is used as a fertilizer.

Other processes used include roasting the matte to produce high grade nickel oxides that are treated using a pressure leach. The solution used for this process is electro and carbonyl refined. In electrorefining an electrolytic cell is used for the refining process. Diaphragm compartments are used to prevent the movement of impurities from the anode to the cathode. This process results in a high quality nickel. In carbonyl refining, the matte is passed through carbon monoxide resulting in nickel and iron carbonyls.

Shaping Process of Nickel

After nickel has gone through the refining process it can be machined into a variety of shapes such as bars and rods, plates, sheets, and tubing. A variety of processes are used to produce these shapes and these are discussed in detail below:

Nickel Extrusion

This is the least common method used for nickel forming. It involved melting the nickel by subjecting it to very high temperatures and then shaping it by forcing the nickel through a die. This results in the formation of nickel sheets, bars, rods and tubing.

Cold Drawing

This method is more common for shaping nickel than nickel extrusion. There is no heat added to this process; instead the nickel tube or wire is drawn through a series of smaller dies in order to reduce its diameter. This process is used in the production of nickel tubes and wires.

Electroless Nickel Plating

This process uses an aqueous solution that contains a chemical reducing agent. A catalytic reduction process of nickel ions occurs in this solution. The ions are deposited without requiring electrical energy. The nickel ions deposited have a uniform size and shape. This is by far the most common way to shape nickel.

What to Consider When Purchasing Nickel

Customers and manufacturers must examine important factors when purchasing nickel to ensure that the nickel material purchased is the right shape and size for the job at hand. Important considerations to note include the expected time of exposure to harsh weather elements such as rain and heat, the strain and stress levels that the nickel will endure, the intended usage of the nickel, and the required dimensions of the nickel material. Another important factor to consider as well is the supplier of the nickel. It‘s essential for both customers and manufacturers to have lengthy conversations with a variety of suppliers in order to determine which supplier offers the best prices, lead times, good secondary services, great delivery policies and great customer service.

Chapter 2: Types and Forms of Nickel Metal

Due to its desirable characteristics, nickel is often combined with other elements to form alloys. Some alloying materials include but are not limited to: chromium, cobalt, copper, and iron. The most common alloy of nickel is stainless steel. It‘s mainly made up of iron, 18 percent chromium, and 8 percent nickel.

Nickel alloys can be classified into the following categories namely:

• Nickel-titanium alloys
• Nickel-chromium-cobalt alloys
• Nickel-chromium-molybdenum alloys
• Nickel-chromium-iron alloys
• Nickel-chromium alloys
• Nickel-molybdenum alloys
• Nickel-copper alloys
• Nickel-iron alloys
• Wrought nickel

Some alloys and forms of nickel are listed below. It‘s important to note that each of the types and forms of nickel listed below fall into a category of nickel alloys listed above.

Brushed Nickel

This type of nickel would have been finished using a wire brush or similar rough surface. This results in the nickel having tiny patterned lines but it still retains its shiny look. Brushed nickel is corrosion resistant however it tarnishes easily. Due to age and exposure, it can develop a milky white tarnish.

However this can be dealt with easily by cleaning the brushed nickel with a mild cleaner or a solution composed of water and white vinegar.

Brushed nickel is useful for making:

• Door knobs
• House numbers
• Kitchen faucets
• Bathroom fittings
• Cabinet hardware
• Lighting fixtures

Casting Alloys

These nickel alloys are formed by melting the alloy and then pouring it into a mold. They are easier to mold than other alloys. They are resistant to heat, corrosion, and wear resistance and are well known for their high strength.

Cupro Nickel

This nickel alloy contains nickel, copper, iron, and manganese. The content of copper in this alloy varies from 60 to 90 percent making it the main component in the alloy. The alloy has a silver color.

It‘s highly resistant to corrosion by seawater, has good thermal conductivity, extremely ductile, and good tensile strength. Uses of cupronickel are:

• Piping and heat exchangers
• Condensers for marine hardware
• Propellers and propeller shafts
• Military equipment
• Steam turbine condensers
• Oil coolers and auxiliary cooling systems
• Desalination plants

Hastelloy

These nickel-based alloys are resistant to corrosion from acids.

Types of Hastelloy nickel-based alloys are listed below:

• Hastelloy C-4 contains 14.5-17.5% chromium, 0-2% cobalt, 14-17% molybdenum, 0-3% iron, 0-1% manganese, and the remaining balance is nickel content. This alloy is mainly used in environments with inorganic acids. Inorganic acids are acids such as sulfuric acid and hydrochloric acid.
• Hastelloy C-22 contains 20-22.5% chromium, 0-2.5% cobalt, 12.5-14.5% molybdenum, 0-3% iron, 0-0.5% manganese, 2.5-3.5%, tungsten and the remaining balance is nickel content. This alloy is also resistant against acid corrosion.
• Hastelloy C-2000 contains 23% chromium, 2% cobalt, 3% iron, 16% molybdenum, and the remaining balance is nickel content. This alloy is mainly used in environments that contain aggressive oxidants.

Inconel Alloy

Inconel alloys contain nickel as the highest percentage of element used and chromium as the second largest element. These alloys are corrosion resistant, oxidation resistant, and suitable for use in extreme environments since they can withstand high stresses. Inconel alloys are difficult to machine and shape.

There are several types of Inconel alloys, some are listed below:

• Inconel 617 contains nickel, cobalt, chromium, and molybdenum. This combination results in an alloy that has improved strength and oxidation resistance. It‘s corrosion resistant even when exposed to highly corrosive environments. It‘s used in making ducting, transition liners, petrochemical processing, heat-treating equipment, production, and gas turbines.
• Inconel 601 contains nickel, iron, and chromium. Its properties include high corrosion resistance, high strength, and it‘s readily welded and machined. It also has high temperature resistance. Its main uses are in fabrication combustion chambers, thermal reactors, insulating cans, and refractory cans.
• Inconel 625 contains 58% nickel, 20-23% chromium, 5% iron, 8-10% molybdenum, 3.15-4.15% niobium, 1% cobalt and trace amounts of sulfur, manganese, aluminum, titanium, silicon, carbon, and phosphorus. It‘s mainly used in steam liner bellows, sheathing for undersea communication cables and some submarine components.
• Inconel 600 contains 72% nickel, 14-17% chromium, 6-10% iron, 1% manganese and trace amounts of carbon, sulfur, silicon, and copper. Its uses include but are not limited to chemical and food processing, heat treating, phenol condensers, soap manufacture, vegetable, and fatty acid vessels. It doesn‘t react with chlorine and chlorine water.
• Inconel 718 contains 50-55% nickel, 19% chromium, 17% iron, 3% molybdenum, 5% niobium, 1% cobalt, 1% aluminum and trace amounts of boron, phosphorus, sulfur, carbon, copper, titanium, manganese, and silicon. Uses include but are not limited to power generating plants, gas turbines, chemical production, combustion cans, and ducting.

Invar Alloy

This is a nickel-iron alloy whose chief property is a low coefficient of thermal expansion. It contains 36% nickel and 64% iron.

It‘s mainly used in:

• Precision instruments
• Clocks
• Seismic creep gauges
• Television shadow-mask frames
• Valves in engines
• Large aerostructure molds

Kovar Alloy

This alloy contains iron, nickel, cobalt and trace amounts of manganese, silicon, and carbon. One of its properties includes having a low coefficient of thermal expansion, this means that as temperature increases there‘s little to no expansion in the material.

It‘s mainly used in glass-to-metals seals in scientific apparatus, conductors in vacuum tubes, X-ray, microwave tubes, and light bulbs.

Monel Alloy

This alloy contains nickel, about 52 to 67% of it, copper and trace amounts of manganese, iron, carbon and silicon. It‘s corrosion resistant, malleable, has a low coefficient of thermal expansion, and high strength.

Uses of monel include but are not limited to:

• Seawater valves, strainer baskets, trolling wire, fixtures and fasteners
• Gasoline tanks, off-shore oil rigs, petroleum stills, processing equipment
• Musical instruments such as trumpets, French horns, tubas, and bass guitar strings
• Kitchen sinks, doorknobs, and decorative screens
• Boilers, chemical tanks, tubes, wires, sheets and plates that are used in the manufacturing of equipment, and parts

There are several types of monel alloys, some are listed below:

• Monel 400 contains 63% nickel, 28-34% copper, 2.5% iron, 2% manganese and trace amounts of sulfur, carbon, and silicon.
• Monel 404 contains 52-57% nickel, 2% iron, 45% coppers and trace amounts of aluminum, manganese, silicon, carbon, and sulfur. Mainly used in the electronics industry due to its low permeability.
• Monel 405 has the same composition as Monel 400. Its main uses are in the chemical, marine, and oil industries. It‘s also used in pickling bat heating coils, making steam generator tubing, and brine heaters. This alloy is corrosion resistant, slightly magnetic at room temperature, resistant to both hydrofluoric and hydrochloric acids and is resistant to steam at high temperatures as well as seawater.
• Monel K-500 contains 64% nickel, 30% copper, 1% iron, 2.8% aluminum and trace amounts of carbon, titanium, and manganese. It‘s mainly used in marine equipment. This is because Monel K-500 is very resistant to the corrosive nature of seawater elements.

Nichrome Alloy

This is a nickel-chromium alloy whose properties are high electrical resistance and high temperature resistance. It has a silvery-gray color. Its main uses are as resistance wire, heating elements in equipment such as space heaters and toasters and as well as in dental restorations.

It‘s also used in the explosives and fireworks industry as a bridgewire in electric ignition systems such as electric matches and model rocket igniters. It‘s also used in ceramics, flame testing as well as in motorcycle mufflers.

Nickel 200

This is wrought nickel which has a purity of about 99.6%. It contains trace elements of iron, manganese, silicon, copper, carbon, and sulfur.

Its uses are:

• Synthetic fibers
• Food processing equipment
• Drums to transport chemicals
• Rocket motors
• Piping
• Handling of foods
• Aerospace and missile components

Nickel Bars and Rods

Nickels rods and bars are straight, they have various shapes including square, circular, and triangular amongst others. It‘s mainly used in applications such as steam turbines in power plants and aircraft gas turbines.

There are several types of nickel bars namely: nickel hex bar, pure nickel alloy round bar, ASTM B160 nickel alloy rod, and nickel alloy square bar to name just a few.

Nickel Plates

This is a form of nickel that is made up of rolled nickel and is used in the construction of buildings and bridges.

Nickel Sheet

This is a flat plane made of nickel or nickel alloys. Nickel sheets have uniform thickness and are thin.

Nickel sheets have various applications such as in the power generation, marine, electronics, and aerospace industry to name just a few.

Nickel Tubing

This is a hollow nickel tube which is either cylindrical or rectangular in shape and can be used to transport fluids or gasses or as equipment components.

Permalloy Nickel Alloy

Permalloy is a nickel alloy that contains 80% nickel and 20% iron. Its properties include high magnetic permeability. This makes it suitable for use as a magnetic core material in electrical and electronic equipment. It's also used in magnetic shielding to block magnetic fields.

Chapter 3: Application and Benefits of Nickel Metal

This chapter will discuss the applications and benefits of nickel metal.

Applications of Nickel Metal

As highlighted before nickel is a versatile metal with a variety of applications. These applications are summarized in the list below:

• The main important application of nickel is as an alloying metal. It can combine with metals such as iron, copper, chromium to name just a few in order to form alloys that are high temperature resistant, corrosion resistant, have a low coefficient of thermal expansion, excellent ductility, great tensile strength, are malleable, and have good electrical conductivity. All these properties prove useful in the construction and production of various equipment and products used in industry and households.
• It‘s useful for making stainless steel.
• Nickel alloys are used in the aviation, marine, chemical, and energy industries.
• Products such as color TV sets, communication sets, surgical instruments, combustion chambers, turbine engine disks are all made from nickel and nickel alloys.
• Nickel is used in electroplating. This is done to prevent or slow down the corrosion of other metals as well as for decorative reasons.
• It‘s also used in the making of rechargeable battery systems that are essential in power tools, transport, and emergency power supply.
• Nickel also acts as a catalyst in several important chemical reactions such as the hydrogenation of vegetable oils, reforming of hydrocarbons, and production of fertilizers, pesticides, and fungicides.
• Because of its corrosion resistance, nickel was at times utilized as a replacement for decorative silver. Nickel was also at times utilized in some nations after 1859 as a cost effective coin metal, but it was replaced in the 20th century in later years, by cost effective stainless steel.
• Nickel naturally has a magnetic field presence meaning that it is a magnetostrictive material.
• Nickel is utilized as a binding agent in the hard metal industry or cemented tungsten carbide. It is utilized in 6% to 12% ratios by weight. Nickel causes the tungsten carbide to be magnetic and enhances resistance to corrosion to the cemented components, though the hardness is lower than for those featuring a cobalt binder.
• About 27% of all nickel manufactured is intended for engineering, 10% for construction and building, 14% for cylindrical products, 20% for metallic goods, 14% for transportations, 11% for electronic products, and 5% for other uses.

Benefits of Nickel Metal

Nickel is 100% recyclable and is of paramount importance in the construction of buildings and certain equipment used in the power and communications industries to name just a few. It‘s tough, corrosion resistant, and hygienic, making it useful in the medical industry. Nickel is rarely used in its purest form, it‘s typically combined with other metals to form alloys that offer ductility and strength at high temperatures.

Nickel‘s ability to withstand high heat minimizes corrosion. What this means is that the metal can be used for many years without having to replace it. It can be used to make jet engines, offshore installations and power generation facilities as a result of its ability to withstand very harsh temperature conditions. Nickel is a principal component in the stainless steel industry.

Drawbacks of Nickel Metal

Despite the multitude of useful applications and good properties of nickel and nickel alloys there are a variety of drawbacks associated with these substances and these are listed below:

• Touching nickel can result in contact dermatitis among individuals with sensitive skin types.
• Nickel occurs naturally and can only be obtained through mining, the negative consequences of mining include alteration of soil profiles, deforestation, contamination of local streams, increase in noise level and dust, and deforestation. Migratory routes of animals can be affected by the infrastructure built to support mining activities. Mining can reduce the living standards of people suited near the area where the mining activities occur.
• Laterite nickel ores require a vast amount of energy for the drying of moisture and removal of chemically bound water from the ores as a result these two major operations are very expensive to carry out.
• Since nickel is a metal it‘s difficult to fabricate as metal fabrication tools are expensive in comparison to plastic fabrication tools. In addition the processes that are carried out after the fabrication process, examples are finishing and painting, are expensive and time consuming. Furthermore metals are not ideal for creating complex designs.
• Nickel alloys such as Inconel are difficult to shape.

Maintenance When Using Nickel Metal

Nickel finishes, often electroplated over a variety of metals such as copper or brass, can tarnish over time due to exposure from chemicals, oil, cleaning products, acidic foods, and many other substances. Harsh weather can also cause the finishes to tarnish as a result nickel plated products require special care. A mild soap can be used along with a clean soft towel to clean the surface. A solution of water and vinegar can also be used to remove dirt and oils. Bleach based cleaners and abrasives should be avoided. Nickel products do not rust though are corrosion resistant.

Conclusion

Nickel is a naturally occurring metallic element which belongs to the metal category known as transition metals. It has two types of ores namely: laterites and magmatic sulfide ores. An ore is a naturally occurring rock which contains one or more minerals that can be extracted, refined and then sold at a profit. The nickel is mined and extracted from the ores using two different methods. Open cut mining, a surface mining method, is used to mine the laterite ore. Laterite ores contain large amounts of water as moisture and hydroxides as a result a large amount of energy has to be used in the drying process and removal of the chemically bound water. Sulfide ores are extracted using underground mining techniques. The ore is crushed and selective floating is used to get some of the nickel from the ore and remove the waste. Magnetic separators are sometimes used as well. Both extraction and refinement of the two ores result in nickel matte, a substance which is a nickel-iron sulfide. Further refinement of the nickel matte can result in nickel with a purity of up to 95%.

Secondary manufacturing processes include casting, molding, separating, and forming. Nickel can be machined into a variety of shapes through processes such as nickel extrusion, cold drawing and Electroless nickel plating. The latter being the most common way to shape nickel. Nickel can be shaped into bars and rods, sheets, plates, tubes and many other shapes. The main use of nickel is in the making of nickel alloys.

Nickel alloys can be classified into the following categories namely: nickel-titanium alloys, nickel-chromium-cobalt alloys, nickel-chromium-molybdenum alloys, nickel-chromium-iron alloys, nickel-chromium alloys, nickel-molybdenum alloys, nickel-copper alloys, nickel-iron alloys, and wrought nickel. Nickel alloys all have different characteristics that make them suitable for a variety of applications.

Nickel is 100% recyclable and has many uses in the power, communications, marine, oil, and medical industries however it has its drawbacks. The most apparent drawback comes from the fact that mining is the only method that can be used to obtain the nickel ore of which mining is harmful to the environment. Furthermore, extracting nickel from laterite ore is expensive as a large amount of energy is required for the drying and smelting process. However nickel and nickel alloys remain an integral part of human civilization as products made from these substances are durable and can last for decades.