Physical characteristics, composition and features of iron metal. Methods of melting non-ferrous metals: melting point, density and specific volume Melting temperature of metals in increasing order

The table shows the melting point of metals t pl , their boiling point t to at atmospheric pressure, density of metals ρ at 25°C and thermal conductivity λ at 27°C.

The melting point of metals, as well as their density and thermal conductivity are given in the table for the following metals: actinium Ac, silver Ag, gold Au, barium Ba, beryllium Be, calcium Ca, cadmium Cd, cobalt Co, chromium Cr, cesium Cs, gallium Ga, hafnium Hf, mercury Hg, indium In, iridium Ir, potassium K, lithium Li, neptunium Np, osmium Os, protactinium Pa, lead Pb, palladium Pd, polonium Po, plutonium Pu, radium Ra, rubidium Pb, rhenium Re, rhodium Rh , ruthenium Ru, antimony Sb, strontium Sr, tantalum Ta, technetium Tc, thorium Th, thallium Tl, uranium U, vanadium V, zinc Zn, zirconium Zr.

According to the table, it can be seen that the melting point of metals varies over a wide range (from -38.83°C for tungsten to 3422°C). Metals such as lithium (18.05°C), cesium (28.44°C), rubidium (39.3°C) and other alkali metals have a low positive melting point.

The most refractory metals are: hafnium, iridium, molybdenum, niobium, osmium, rhenium, ruthenium, tantalum, technetium, tungsten. The melting point of these metals is above 2000°C.

Let's give examples of melting point of metals, widely used in industry and in everyday life:

• melting point of aluminum 660.32 °C;
• copper melting point 1084.62 °C;
• melting point of lead 327.46 °C;
• melting point of gold 1064.18 °C;
• melting point of tin 231.93 °C;
• the melting point of silver is 961.78 °C;
• The melting point of mercury is -38.83°C.

Rhenium Re has the maximum boiling point of the metals presented in the table - it is 5596°C. Also, metals belonging to the group with a high melting point have high boiling points.

In the table it ranges from 0.534 to 22.59, that is, the lightest metal is , and the heaviest metal is osmium. It should be noted that osmium has a density greater than even plutonium at room temperature.

The table varies from 6.3 to 427 W/(m deg), thus the worst conductor of heat is a metal such as neptunium, and the best heat-conducting metal is silver.

Melting point of steel

A table of melting temperature values ​​for common grades of steel is presented. Steels for castings, structural, heat-resistant, carbon and other classes of steels are considered.

The melting point of steel ranges from 1350 to 1535°C. The steels in the table are arranged in order of increasing melting point.

Sources:

1. Volkov A.I., Zharsky I.M. Large chemical reference book. - M: Soviet School, 2005. - 608 p.
2. Physical quantities. Directory. A. P. Babichev, N. A. Babushkina, A. M. Bratkovsky and others; Ed. I. S. Grigorieva, E. Z. Meilikhova. - M.: Energoatomizdat, 1991. - 1232 p.

The melting point of iron is an important indicator of the production technology of the metal and its alloys. When smelting raw materials, physical and Chemical properties ore and metal.

The most common chemical element on Earth.

Physical and chemical properties of iron

• Chemical element number 26 is the most abundant in solar system. According to research, the iron content in the Earth's core is 79–85.5%. In terms of abundance in the planet's crust, it is second only to aluminum.
• The metal in its pure form is white with a silver tint and is distinguished by its ductility. The presence of impurities determines its physical parameters. Iron tends to react to a magnet.
• For this chemical element characterized by polymorphism that occurs when heated. Increased concentrations of the metal are observed in areas of rock eruptions. Industrial deposits are formed as a result of external and internal processes occurring in the earth's crust.
• River water contains approximately 2 mg/l of metal, and the figure for sea water is 100–1000 times less.
• Iron has several oxidation states, which determine its geochemical characteristics in a certain environment. In its neutral form, the metal is found in the Earth's core.
• Iron oxide is the main form found in nature, and iron oxide is located in the uppermost part of the earth's crust as part of sedimentary formations.
• The content of chemical element No. 26 in minerals with an unstable composition increases with a decrease in the temperature gradient. Boiling occurs when heated to + 2861 °C. The specific heat of fusion is 247.1 KJ/kg.

Metal mining

Among the ores containing iron, the raw material for industrial production are:

• hematite;
• goethite;
• magnetite.

Goethite and hydrogoethite form formations in the weathering crust that are hundreds of meters in size. In the shelf zone and lakes, colloidal solutions of minerals form oolites (leguminous iron ores) as a result of precipitation.

Pyrite and pyrrhotite, widely occurring iron minerals in nature, are used as raw materials for the production of sulfuric acid.

Commonly occurring iron minerals also include:

• siderite;
• lellingitis;
• marcasite;
• ilmenite;
• is violent.

The mineral melanterite, which is fragile green crystals with a glassy luster, is used in the pharmaceutical industry for the production of iron-containing preparations.

The main deposit of this metal is located in Brazil. Recently, attention has been focused on mining nodules present on the seafloor that contain iron and manganese.

Melting iron

What determines the melting point of iron?

Metal production involves various technologies its extraction from ore raw materials. The most common method for smelting iron is the blast furnace method.

Before smelting the metal, it is reduced in a furnace at a temperature of +2000 °C. To extract impurities, flux is added, which decomposes when heated to an oxide, followed by combination with silicon dioxide and the formation of slag.

In addition to the blast furnace method, iron smelting is carried out by roasting crushed ore with clay. The mixture is formed into pellets and processed in a hydrogen reduction furnace. Further smelting of iron is carried out in electric furnaces.

Production of alloys in furnaces.

The properties of a metal depend on the purity of the material. For technically pure iron, the melting point is +1539 °C. Sulfur is a harmful impurity. It can only be extracted from a liquid solution. Chemically pure material obtained by electrolysis of metal salts.

Metal alloys

In its pure form, this material is soft, so carbon is added to the composition to increase strength.

In metallurgy, iron alloys are called ferrous metals.

Depending on the components of the alloy, the properties of the materials change. The melting point of iron also changes in the presence of alloy components.

The specific heat of fusion of steel is 84 kJ. This indicator means that at the melting temperature of steel, 84 kJ of energy is required to transfer 1 kg of alloy from a crystalline to a liquid state.

Compounds of different metals form alloys. Specific heat of fusion cast iron is 96–140 kJ. Cast iron contains up to 4% carbon, 1.5% manganese, up to 4.5% silicon and impurities in the form of sulfur and phosphorus. There are white and gray alloys.

In white, part of the carbon is in the iron carbide compound. This alloy is brittle and hard. It is intended for the manufacture of structures and parts.

A gray alloy containing carbon in the form of graphite, it is easy to process. Pig iron is smelted from iron ore in blast furnaces. The smelting of ore is accompanied recovery reaction iron from carbon oxides.

Most substances can melt with increasing volume when heated. For cast iron with a volume of 1000 cm³, this figure is 988–994 cm³.

Cast iron is a raw material for the production of steel, characterized by carbon content (not higher than 2.14%).

By chemical composition distinguish steel:

• alloyed;
• carbon

Carbon steel contains impurities of sulfur, phosphorus and silicon. It is characterized by low electrical properties, low strength, and is easily susceptible to corrosion.

The presence of alloy additives gives steel new technical properties. The following are used as additional components:

• molybdenum;
• nickel;
• tungsten;
• chromium;
• vanadium.

High-alloy steel contains no more than 10% additives. The alloy is durable. The technology for producing steel from cast iron allows us to obtain high-quality material for the production of:

Steel is used as a raw material in various industries. Without it, it is impossible to imagine aircraft manufacturing, shipbuilding, the automotive industry and many other production areas.

In the metallurgical industry, one of the main areas is the casting of metals and their alloys due to the low cost and relative simplicity of the process. Molds with any shape and various dimensions can be cast, from small to large; It is suitable for both mass and customized production.

Casting is one of the oldest areas of working with metals, and begins around the Bronze Age: 7-3 millennium BC. e. Since then, many materials have been discovered, leading to advancements in technology and increased demands on the foundry industry.

Nowadays, there are many directions and types of casting, differing in technological process. One thing remains unchanged - the physical property of metals to transition from solid to liquid, and it is important to know at what temperature melting begins different types metals and their alloys.

Metal melting process

This process refers to the transition of a substance from a solid to a liquid state. When the melting point is reached, the metal can be in either a solid or liquid state; further increase will lead to the complete transition of the material into a liquid.

The same thing happens when solidifying - when the melting limit is reached, the substance will begin to transition from a liquid to a solid state, and the temperature will not change until complete crystallization.

It should be remembered that this rule only applies to pure metal. Alloys do not have a clear temperature boundary and undergo state transitions some range:

1. Solidus is the temperature line at which the most fusible component of the alloy begins to melt.
2. Liquidus is the final melting point of all components, below which the first alloy crystals begin to appear.

It is impossible to accurately measure the melting point of such substances; the point of transition of states is indicated by a numerical interval.

Depending on the temperature at which metals begin to melt, they are usually divided into:

• Low-melting, up to 600 °C. These include tin, zinc, lead and others.
• Medium melting, up to 1600 °C. Most common alloys, and metals such as gold, silver, copper, iron, aluminum.
• Refractory, over 1600 °C. Titanium, molybdenum, tungsten, chromium.

There is also a boiling point - the point at which the molten metal begins to transition into a gaseous state. This is a very high temperature, typically 2 times the melting point.

Effect of pressure

The melting temperature and the equal solidification temperature depend on pressure, increasing with its increase. This is due to the fact that with increasing pressure the atoms come closer to each other, and in order to destroy the crystal lattice they need to be moved away. At increased pressure, greater thermal energy is required and the corresponding melting temperature increases.

There are exceptions when the temperature required to transform into a liquid state decreases with increased pressure. Such substances include ice, bismuth, germanium and antimony.

Melting point table

It is important for anyone involved in the metallurgical industry, whether a welder, foundry worker, smelter or jeweler, to know the temperatures at which the materials they work with melt. The table below shows the melting points of the most common substances.

Melting point table metals and alloys

In addition to the melting table, there are many other supporting materials. For example, the answer to the question what is the boiling point of iron lies in the table of boiling substances. In addition to boiling, metals have a number of other physical properties, such as strength.

Strength of metals

In addition to the ability to transition from solid to liquid, one of the important properties A material is its strength - the ability of a solid body to resist destruction and irreversible changes in shape. The main indicator of strength is the resistance that occurs when a pre-annealed workpiece breaks. The concept of strength does not apply to mercury because it is in a liquid state. The designation of strength is accepted in MPa - Mega Pascals.

The following groups exist strength of metals:

• Fragile. Their resistance does not exceed 50MPa. These include tin, lead, soft-alkaline metals
• Durable, 50−500 MPa. Copper, aluminum, iron, titanium. Materials of this group are the basis of many structural alloys.
• High strength, over 500 MPa. For example, molybdenum and tungsten.

Metal strength table

The most common alloys in everyday life

As can be seen from the table, the melting points of elements vary greatly even among materials commonly found in everyday life.

Thus, the minimum melting point of mercury is -38.9 °C, so at room temperature it is already in a liquid state. This explains why household thermometers have a lower mark of -39 degrees Celsius: below this indicator, mercury turns into a solid state.

Solders most common in household use, contain a significant percentage of tin, which has a melting point of 231.9 °C, so most solders melt at operating temperature soldering iron 250−400°C.

In addition, there are low-melting solders with a lower melt limit, up to 30 °C, and are used when overheating of the materials being soldered is dangerous. For these purposes, there are solders with bismuth, and the melting of these materials lies in the range from 29.7 - 120 °C.

Melting of high-carbon materials, depending on alloying components, ranges from 1100 to 1500 °C.

The melting points of metals and their alloys are in a very wide temperature range, from very low temperatures (mercury) to several thousand degrees. Knowledge of these indicators, as well as other physical properties, is very important for people who work in the metallurgical field. For example, knowledge of the temperature at which gold and other metals melt will be useful to jewelers, foundries and smelters.

The melting point of a metal is the minimum temperature at which it changes from solid to liquid. When melting, its volume practically does not change. Metals are classified by melting point depending on the degree of heating.

Low-melting metals

Low-melting metals have a melting point below 600°C. These are zinc, tin, bismuth. Such metals can be melted by heating them on the stove, or using a soldering iron. Low-melting metals are used in electronics and technology to connect metal elements and wires for the movement of electric current. The temperature is 232 degrees, and the zinc is 419.

Medium melting metals

Medium-melting metals begin to transform from solid to liquid at temperatures from 600°C to 1600°C. They are used to make slabs, reinforcements, blocks and other metal structures suitable for construction. This group of metals includes iron, copper, aluminum, and they are also part of many alloys. Copper is added to alloys precious metals such as gold, silver, platinum. 750 gold consists of 25% alloy metals, including copper, which gives it a reddish tint. The melting point of this material is 1084 °C. And aluminum begins to melt at a relatively low temperature of 660 degrees Celsius. This is a lightweight, ductile and inexpensive metal that does not oxidize or rust, therefore it is widely used in the manufacture of tableware. The temperature is 1539 degrees. This is one of the most popular and affordable metals, its use is widespread in the construction and automotive industries. But due to the fact that iron is subject to corrosion, it must be additionally processed and covered with a protective layer of paint, drying oil, or prevent moisture from entering.

Refractory metals

The temperature of refractory metals is above 1600°C. These are tungsten, titanium, platinum, chromium and others. They are used as light sources, machine parts, lubricants, as well as in the nuclear industry. They are used to make wires, high-voltage wires, and are used to melt other metals with a lower melting point. Platinum begins to transition from solid to liquid at a temperature of 1769 degrees, and tungsten at a temperature of 3420°C.

Mercury is the only metal that is in a liquid state under normal conditions, namely, normal atmospheric pressure and average temperature. environment. The melting point of mercury is minus 39°C. This metal and its vapors are poisonous, so it is used only in closed containers or in laboratories. A common use of mercury is as a thermometer to measure body temperature.

The melting point of metals, which varies from the smallest (-39 °C for mercury) to the highest (3400 °C for tungsten), as well as the density of metals in the solid state at 20 °C and the density of liquid metals at the melting point are given in the melting table for non-ferrous metals .

Table 1. Melts of non-ferrous metals

Welding and melting of non-ferrous metals

Copper welding . The melting temperature of Cu metal is almost six times higher than the melting temperature of steel; copper intensively absorbs and dissolves various gases, forming oxides with oxygen. Copper oxide II forms a eutectic with copper, the melting point of which (1064°C) is lower than the melting point of copper (1083°C). When liquid copper solidifies, the eutectic is located along the grain boundaries, making the copper brittle and prone to cracking. Therefore, the main task when welding copper is to protect it from oxidation and actively deoxidize the weld pool.

The most common gas welding of copper is with an oxide-acetylene flame using torches that are 1.5...2 times more powerful than a torch for welding steel. The filler metal is copper rods containing phosphorus and silicon. If the thickness of the products is more than 5...6 mm, they are first heated to a temperature of 250...300°C. The flux used in welding is roasted borax or a mixture consisting of 70% borax and 30% boric acid. To increase mechanical properties and improve the structure of the deposited metal, copper after welding is forged at a temperature of about 200...300°C. Then it is heated again to 500-550°C and cooled in water. Copper is also welded using the electric arc method using electrodes, in a stream of protective gases, under a layer of flux, on capacitor machines, and by friction.

Welding brass . Brass is an alloy of copper and zinc (up to 50%). The main contamination in this case is the evaporation of zinc, as a result of which the seam loses its quality and pores appear in it. Brass, like copper, is mainly welded with an acetylene oxidizing flame, which creates a film of refractory zinc oxide on the surface of the bath, reducing further burnout and evaporation of zinc. The fluxes used are the same as those used when welding copper. They create slags on the surface of the pool, which bind zinc oxides and make it difficult for vapors to escape from the weld pool. Brass is also welded in shielding gases and on contact machines.

Bronze welding . In most cases, bronze is a casting material, so

Welding is used to correct defects or during repairs. Metal electrode welding is most often used. The filler metal is rods of the same composition as the base metal, and the fluxes or electrode coating are chloride and fluoride compounds of potassium and sodium.

. The main factors that make aluminum welding difficult are its low melting point (658°C), high thermal conductivity (about 3 times higher than the thermal conductivity of steel), the formation of refractory aluminum oxides, which have a melting point of 2050°C, so the technology for melting non-ferrous metals , such as copper or bronze, is not suitable for melting aluminum. In addition, these oxides react poorly with both acidic and basic fluxes, and therefore are difficult to remove from the seam.

Gas welding of aluminum with an acetylene flame is most often used. IN last years Automatic arc welding with metal electrodes under submerged arcs and in argon has also spread significantly. For all welding methods, except argon arc, fluxes or electrode coatings are used, which contain fluoride and chloride compounds of lithium, potassium, sodium and other elements. As a filler metal in all welding methods, wire or rods of the same composition as the base metal are used.

Aluminum can be welded well with an electron beam in a vacuum, on contact machines, electroslag and other methods.

Welding of aluminum alloys . Aluminum alloys with magnesium and zinc are welded without

special complications, just like aluminum. An exception is duralumin - alloys of aluminum and copper. These alloys are thermally strengthened after quenching and subsequent aging. When the melting temperature of non-ferrous metals exceeds 350°C, a decrease in strength occurs in them, which is not restored by heat treatment. Therefore, when welding duralumin in the heat-affected zone, the strength decreases by 40...50%. If duralumin is welded in shielding gases, then this reduction can be restored by heat treatment to 80...90% in relation to the strength of the base metal.

Welding of magnesium alloys . At gas welding Fluoride fluxes must be used, which, unlike chloride fluxes, do not cause corrosion welded joints. Arc welding of magnesium alloys with metal electrodes due to the poor quality of welds has not yet been used. When welding magnesium alloys, significant grain growth is observed in the near-seam areas and strong development of columnar crystals in weld. Therefore, the tensile strength of welded joints is 55...60% of the tensile strength of the base metal.

Table 2. Physical properties industrial non-ferrous metals

Crucible melting

An integral component of the production of metal and metal products is the use during production process crucibles for the production, smelting and remelting of both ferrous and non-ferrous metals. Crucibles are an integral part of metallurgical equipment for casting various metals, alloys, and the like.

Ceramic crucibles for melting non-ferrous metals have been used for melting metals (copper, bronze) since ancient times.

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