Type Of Protective Atmosphere - Knowledge - Hangzhou Hangshen Energy-Saving Furnace Co.,Ltd

1 Hydrogen (Hydrogen)

Hydrogen (H2) molar mass 2.016g / mol, density 0.0899kg / m3, melting point -259 ° C, boiling point -252.8 ° C, ignition temperature 572 ° C; and air mixed explosion limit lower limit H (H2) = 4.0%, the upper limit ψ (H2) = 75%; the calorific value is 2800 kJ and the low value is 10790 kJ. It dissolves very little in various liquids. H2 is a strong reducing gas, which is inactive at normal temperature, but is very active at high temperatures or in the presence of a catalyst, and can be directly combined with many non-metals and metals. All bottled hydrogen contains traces of water and oxygen, and trace amounts of impurities such as methane, nitrogen, carbon monoxide and carbon dioxide may be present, depending on the method of preparation.

Hydrogen is often used as a heat treatment protective gas for the bright annealing of low carbon steel, stainless steel, electrical steel and non-ferrous metals, and the sintering of tungsten carbide and titanium carbide.

2 Nitrogen (Nitrogen)

The molar mass of nitrogen (N2) was 28.0134 g/mol, the density was 1.2507 kg/m3, the melting point was -209.86 ° C, and the boiling point was -195.8 °C. Its chemical properties are inactive, but at high temperatures, nitrogen molecules acquire enough energy to cause their covalent bond to break, combine with certain metals or non-metals, and directly combine with hydrogen and oxygen. As a heat treatment gas, nitrogen is stable at 1000 ° C and is a neutral gas. It is active at 1000 ° C or higher and can nitridify steel.

Nitrogen is used as the main gas in the nitrogen-based atmosphere, and is mainly used for bright annealing, quenching and carbonitriding of steel parts.

3 Ammonia (Ammonia)

The molar mass of ammonia (NH3) was 17.03 g/mol and the density was 0.7710 kg/m3. Pressurize at room temperature to liquefy into a colorless liquid (supervised temperature 132.4 ° C, monitoring pressure 11.22 Mpa), boiling point -33.5 ° C. The ammonia is easily solidified into a snowy solid with a melting point of -77.7 °C. Ammonia is soluble in water, ethanol and ether and decomposes into nitrogen and hydrogen at high temperatures. In the presence of a catalyst, ammonia can be oxidized to ammonia monoxide.

Ammonia is a nitriding agent for gas nitriding and ion nitriding. The ammonia decomposition atmosphere and the ammonia combustion atmosphere can be used as a protective atmosphere for the heating of steel parts, powder metallurgy sintering and beryllium bronze parts.

4 Propane (Propane)

The molar mass of propane (C3H8) was 44.9 g/mol, the density was 0.5005 kg/m3, the boiling point was -42.17 ° C, and the melting point was -189.9 °C. The heating value of propane was 90730 kJ/m3, the ignition temperature was 505 °C, the volume fraction of the lower limit of ignition was 2.4%, the upper limit was 9.5%, and the theoretical combustion temperature was 1977 °C.

Propane can be used as a raw material gas for the preparation of endothermic and exothermic atmospheres, mainly for workpiece carburizing, carbonitriding, nitrocarburizing and annealing, normalizing, quenching and tempering. Propane is a gas at normal temperature and normal pressure, and can be pressurized and liquefied.

5 Butane

The molar mass of butane (C4H10) was 58.12 g/mol, the density was 0.5783 kg/m3, the boiling point was -0.5 ° C, and the melting point was -138.3 °C. The calorific value of butane is 118,490 kJ/m3, the ignition temperature is 431 °C, the volume fraction of the lower limit of ignition temperature is 1.8%, the volume fraction of the upper limit is 8.4%, and the theoretical combustion temperature is 1982 °C.

6 Methanol

Molecular formula CH3OH

Molecular weight 32 specific gravity 0.792

Boiling point 64.7 ° C

Relative gravity of methanol vapor (air = 1) 1.11

Vapor pressure (20 ° C) 96mmHg

Lower limit of gas combustion 6 Vol%

Feeling limit 200PPM

Environment allows the highest concentration of 200PPM

Flash point 9.5 ° C (closed) 16 ° C (opening)

Spontaneous ignition point 470 ° C

Methanol cracking reaction CH3OH CO+2H2