The physical properties of aluminum

Aluminum is a metallic element, the element symbol is Al, is a silver white light metal. It's malleable.

Physical properties

In moist air can form an oxide film to prevent metal corrosion. Aluminum powder treated with acid is heated in the air and burns violently with a blinding white flame.

It is easily soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, insoluble in water, but can react with hot water slowly to produce aluminum hydroxide, with relative density of 2.70, elastic modulus of 70Gpa, Poisson's ratio of 0.33. Melting point is 660 ℃. The boiling point of 2327 ℃. It is widely used for its light, good electrical and thermal conductivity, high reflectance and oxidation resistance. The aluminum used to make daily dish utensils is usually called "steel" or "steel". The thermal expansion coefficient of Al at 25 ° C is 0.0000236mm/ ° C or 23.6 PPM *k-1.

The effect of aluminum on microstructure and heat treatment of steel

① Aluminum has a strong affinity with oxygen and nitrogen, and is a deoxynitrogen-fixing agent in steelmaking.

② Aluminum strongly reduces the austenite phase region in steel.

③ The affinity of aluminum and carbon is small, and the carbide of aluminum does not appear in steel generally. Aluminum strongly promotes the graphitization of carbon, and the addition of strong magnetizing elements such as chromium, titanium, vanadium and niobium can inhibit the graphitization of aluminum.

(4) Aluminum refines the essential grain of steel and increases the coarsening temperature of steel grain. However, when the content of solid aluminum in steel exceeds a certain value, the austenite grain is easy to grow and coarsening.

(5) Aluminum increases the martensite transition temperature of steel and reduces the residual austenite content after quenching, which is opposite to other alloying elements except cobalt.

Second, the influence of aluminum on the mechanical properties of steel

① Aluminum reduces the sensitivity of steel to notch, reduces or eliminates the aging phenomenon of steel, especially reduces the ductile and brittle transition temperature of steel, and improves the toughness of steel at low temperature.

(2) Aluminum has a greater solution strengthening effect, and high aluminum steel has the advantage of higher specific strength. The high temperature strength and durable strength of ferro-aluminum alloy of ferritic form are higher than those of Cr13 steel, but the plasticity and toughness of ferro-aluminum alloy at room temperature are low and it is difficult to be processed by cold deformation.

③ The comprehensive properties of Austenitic iron, aluminum and manganese series steel are better.

The influence of aluminum on the physical, chemical and process properties of steel

① Aluminum added to Fe-Cr alloy can reduce its resistance temperature coefficient, which can be used as an electric heating alloy material.

Electrothermal alloy wire

(2) Aluminum and silicon have similar effects on reducing the core loss of transformer steel.

(3) When the aluminum content reaches a certain value, the surface of the steel will be passivated, so that the steel has corrosion resistance in the oxidized acid, and improve the corrosion resistance to hydrogen sulfide. Aluminum is detrimental to corrosion resistance of steel in chlorine and chloride atmospheres.

(4) Aluminum nitride layer is formed on the surface of aluminum containing steel after nitriding, which can improve the hardness and fatigue strength and wear resistance.

(5) Aluminum added to steel as an alloying element can significantly improve the oxidation resistance of steel. Aluminum plating or aluminizing on the surface of steel can improve its oxidation resistance and corrosion resistance, which can be used in the manufacture of solar water heaters.

⑥ Aluminum has adverse effects on hot working properties, weldability and machinability.

Four, the application of aluminum in steel

① Aluminum in general steel mainly plays the role of deoxidation and grain size control.

② Aluminum, as one of the main alloy elements, is widely used in special alloys, including nitriding steel, stainless acid-resistant steel, heat-resistant steel, electric heating alloy, hard magnetic and soft magnetic alloy, etc.

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