Low temperature salts are used for a wide variety of unit operations, such as solution heat treating of aluminum, or martempering and austempering of steels. They are usually mixtures of various nitrates and nitrates of sodium and potassium. These salts are completely molten at 150°C.
Full Answer
What are the uses of molten salt baths in metal treating?
The uses of molten salt baths in metal treating applications such as heat treatment, cementation, cleaning, finishing and brazing are reviewed. The potential of some promising new applications is also assessed.
What are the uses of metalloid salts?
Molten salts are also used as fluxing agents for preparing steel prior to zinc and aluminum hot dipping [112, 113] . 6.2. Chemical conversion coatings Oxydant baths have long been used in order to produce oxide coatings on the surface of steels either as decoration or for protection against corrosion.
What salts are used in heat treatment?
Heat treatment salts are made of inorganic compounds such as blends of several different salts to provide the desired melting point and working range and chemical characteristics. For example, potassium nitrate and sodium nitrate salts are used in aluminum solution treating. Cyanide salts are used in carburizing, casing or case hardening.
What are the medical uses of gold salts?
Investigation of medical applications of gold salts began at the end of the 19th century, when gold cyanide demonstrated efficacy in treating Mycobacterium tuberculosis in vitro. The use of injected gold salts is indicated for rheumatoid arthritis.
Which metal is used in medical treatment?
Platinum is a precious metal that has been used in a variety of medications and tools since the early 1970s. Its dense, malleable properties are essential to the production of pacemakers, catheters, stents and even cancer therapies.
What are heavy metal salts?
In the second group are the salts of the heavy metals—lead, copper, zinc, nickel, cadmium and mercury, which are definitely toxic at concentrations from o-ooooiiV upwards.
Why are transition elements are used in medicine?
Transition metals exhibit different oxidation states and can interact with a few negatively charged molecules. These properties of transition metals led to the development of metal-based drugs with promising pharmacological application and unique therapeutic opportunities.
Is alum a heavy metal?
Characteristics of Heavy Metals Examples of heavy metals include lead, mercury, cadmium, sometimes chromium. Less commonly, metals including iron, copper, zinc, aluminum, beryllium, cobalt, manganese and arsenic may be considered heavy metals.
What are heavy metals used for?
Heavy metals are relatively scarce in the Earth's crust but are present in many aspects of modern life. They are used in, for example, golf clubs, cars, antiseptics, self-cleaning ovens, plastics, solar panels, mobile phones, and particle accelerators.
What are 5 heavy metals?
Frontiers | Toxic Mechanisms of Five Heavy Metals: Mercury, Lead, Chromium, Cadmium, and Arsenic | Pharmacology.
What alkali metal is used in medicine?
Lithium salts are used in the prophylaxis and treatment of mania, and in the prophylaxis of BD and recurrent depression. Lithium therapy is taken orally, usually as lithium carbonate or lithium citrate with a total dose of up to 30 mmol/day.
Which minerals are used in medicine?
MineralsDrugDrug DescriptionChromiumAn ingredient found in a variety of supplements and vitamins.Sodium zirconium cyclosilicateA potassium binder used to treat hyperkalemia.Ferrous sulfate anhydrousAn iron supplement used to prevent or treat iron deficiency anemia.43 more rows
Why metal complexes are used in medicine?
Metal complexes have become an emerging tool in drug discovery being widely used as therapeutic compounds to treat several human diseases such as carcinomas, lymphomas, infection control, diabetes, anti-inflammatory, and neurological disorders [8, 9].
What metal is in makeup?
All types of makeup, whether natural or high-end, may contain heavy metals such as lead, aluminum, cadmium, arsenic, or mercury, to name a few. Heavy metals will not be listed on the ingredients list because they are contaminants.
What's the heaviest metal?
osmiumThe Heaviest Metal. The heaviest metal is osmium, which has, bulk for bulk, nearly twice the weight of lead. The specific gravity of gold is about 19 1/4, while that of osmium is almost 22 1/2.
Is arsenic A metal?
Arsenic (atomic number, 33; relative atomic mass, 74.92) has chemical and physical properties intermediate between a metal and a non-metal, and is often referred to as a metalloid or semi-metal. It belongs to Group VA of the Periodic Table, and can exist in four oxidation states: –3, 0, +3, and +5.
Metal Pickling
Metal treatment processes start with degreasing steps mainly carried out with alkaline agents. more
Electroplating
Electroplating processes are used to functionalize metal and non-metal surfaces for enhanced corrosion protection, more
Tribology
Solid lubricants such as Pyrophosphates are used to alter the tribological properties of metal surfaces. more
What is salt bath heat treatment?
Salt bath heat treatment is a heat treatment process comprising an immersion of the treated part into a molten salt, or salts mixture. 2 There are numerous benefits of heat treatment in salt baths, the most prevalent is that they provide faster heating.
Why use salt baths for quenching?
Using salt baths also helps with a controlled cooling conditions during quenching. In conventional quenching operation, typically either water or oil are used as the quenching media and the high cooling rate provided by water/oil may cause cracks and distortion.
What temperature does iron have to be to be bainite?
Typical Austempering Heat Treatment Cycle in Ductile Iron. When heated to temperatures below 730°C (1346°F), the pure metal iron has a body-centered cubic structure; if heated above this temperature, the structure will change to a face-centered cubic.
What are the advantages of salt baths?
Salt baths also provide low surface oxidation and decarburization, as the contact of the hot work part with the atmosphere is minimized when the part is treated in the salt bath. 2 There are additional advantages to salt heat treat: Most of the heat is extracted during quenching by convection at a uniform rate.
What is heat treated steel?
According to the ASM International’s Heat Treating Society, about 80 percent of heat treated parts are made of steel, such as bars and tubes, as well as parts that have been cast, forged, welded, machined, rolled, stamped, drawn, or extruded. 1. SAE Designation.
What industries use heat treated parts?
Numerous industries utilize heat treated parts, including those in the automotive, aerospace, information technology, and heavy equipment sectors . Specifically, manufacturers of items such as saws, axes, cutting tools, bearings, gears, axles, fasteners, camshafts, and crankshafts all rely on heat treating to make their products more durable ...
What is heat treating?
Heat treating is a process in which metal is heated to a predetermined temperature and then cooled in a particular manner to alter its internal structure for obtaining a desired degree of physical, mechanical and metallurgical properties.
What are the side effects of gold salts?
Other side effects. Other side effects of gold salts include kidney damage, itching rash, and ulcerations of the mouth, tongue, and pharynx. Approximately 35% of patients discontinue the use of gold salts because of these side effects. Kidney function must be monitored continuously while taking gold salts.
Why is the use of gold compounds decreasing?
The use of gold compounds has decreased since the 1980s because of numerous side effects and monitoring requirements, limited efficacy, and very slow onset of action. Most chemical compounds of gold, including some of the drugs discussed below, are not salts, but are examples of metal thiolate complexes .
Why do gold salts discolor skin?
Skin discoloration occurs when gold salts are taken on a regular basis over a long period of time. Excessive intake of gold salts while undergoing chrysotherapy results – through complex redox processes – in the saturation by relatively stable gold compounds of skin tissue and organs (as well as teeth and ocular tissue in extreme cases) ...
What are the ionic compounds of gold?
Ionic chemical compounds of the element. Sodium aurothiomalate. Auranofin. Gold salts are ionic chemical compounds of gold. The term, "gold salts" is a misnomer, and is the term for the gold compounds used in medicine. "Chrysotherapy" and "aurotherapy" are the applications of gold compounds to medicine. Contemporary research on the effect of gold ...
Can gold salts be administered orally?
Administration. Gold salts for rheumatoid arthritis are administered by intramuscular injection but can also be administered orally (although the efficacy is low). Regular urine tests to check for protein, indicating kidney damage, and blood tests are required.
Is gold salt good for arthritis?
Indications. The use of injected gold salts is indicated for rheumatoid arthritis. Its uses have diminished with the advent of newer compounds such as methotrexate and because of numerous side effects. The efficacy of orally administered gold is more limited than injecting the gold compounds.
Advantages of Molten Salt Heat Treating
Parts that are heated in salt baths are heated by conduction. The thermal mass of the molten salt provides a large thermal source for heating of parts. Heating of parts in a salt bath is much more rapid than in air or atmosphere furnace. The heat-up of the parts is only limited by the thermal conductivity of the part.
Types of Salts – Salt Composition
There are several different types of heat-treating operations that can be performed in molten salts. The first is to solution heat treat the part (austenitize in steel) to bring it to the desired temperature. The second operation is to quench the part in the molten salt as part of martempering operation or austempering.
Low Temperature (150°–620°C)
Low temperature salts are used for a wide variety of unit operations, such as solution heat treating of aluminum, or martempering and austempering of steels. They are usually mixtures of various nitrates and nitrates of sodium and potassium. These salts are completely molten at 150°C.
Medium Temperature (650°–982°C)
Since nitrates and nitrites are unstable at temperatures above 620°C, another type of molten salt chemistry is required. Molten salts in this class of salts are mixtures of sodium chloride (NaCl), potassium chloride (KCl), calcium chloride (CaCl2), sodium carbonate (Na2CO3), and barium chloride (BaCl2).
High Temperature (982°C–1287°C)
The high temperature molten salt baths are predominately barium chloride, with either potassium chloride or sodium chloride added to the composition. However, the most common bath is barium chloride with a small amount (up to 5 percent) of silica added as a bath rectifier.
Specialized Salts – Nitriding and Carburizing
There are also specialized salts for molten salt carburizing and nitriding, as well as salts for blackening or bluing steels.
Conclusions
In this column, the advantages of the use of molten salt were illustrated. The salt composition of the various temperature ranges of salt were explained. In later columns, the application of molten salt quenching (martempering and austempering) will be discussed.
