Self-propagating High-temperature Synthetic process

Self-propagating high temperature synthesis (SHS) is used to describe a process in which the initial reagents (usually powders), when ignited, spontaneously transform into products due to the exothermitic heat of reaction.

A well-known example of SHS reaction is the thermite reaction given below:

This reaction generates temperatures above the melting point of alumina and is used in the thermit welding process for joining railway lines.

Several other terminologies – such as combustion synthesis, gasless combustion or self-propagating exothermic reaction – are used to describe the process.

Main properties of ceramic lined pipe

Item	Index
Content of Alumina	≥95%
Density	≥3.5 g/cm3
Rockwell Hardness	≥80 HRA
Impact Strength	≥850 Mpa
Bending Strength	≥290MPa
Breaking Temper	≥4.8MPa·m1/2
Coefficient of Linear Thermal Expansion	20W/m.K

The combination of high rigidity of ceramic and high elasticity of steel gives the pipe unmatchable features as an abrasion resistant, heat resistant and corrosion resistant material for use in the fields of power generation, metallurgy, mining, and chemical industry etc.. It has many advantages over steel pipes, cast stone pipes, and steel-plastic compound pipes.

Ceramic Lined Steel Pipe and Elbows:

1.1 The Manufacturing Process of Ceramic Lined Steel Pipe and Elbows:
Ceramic (Corundum: a-Al2O3) lined abrasion resistant straight pipe and fittings are lined with highly abrasion resistant ceramic by SHS ——-Self-propagating High-temperature Synthetic process.

The composite pipe is composed of three layers: ceramic, intermediate, and steel layers. The ceramic layer is formed by molten alumina at a temperature above 2500 degree.
The molten alumina produced from the reaction Fe2O3+2Al=2Fe+Al2O3 spreads on the inside wall of the steel pipe under the influence of a centrifugal force, then solidifies, so the ceramic layer has high density and smooth surface and bonds to the steel pipe. They are widely used to convey highly abrasive material such as fly ash and any other fine powder material in mine, thermo power generating, coal processing plant, metallurgy, construction, etc. The service life is 10 to 20 times longer than normal steel pipe.

a). High Abrasion Resistant:
Vickers hardness of the corundum lining is HV1100 to1500, as high as that of tungsten-cobalt hard alloys, and the abrasion resistance is 20 times as carbon steel pipes. A composite elbow was used in a mining plant for about fifty thousands hours.

The general service life of common steel elbow is about 700 hours.

b). Corrosion Resistant:
Corundum is a neutral material, and is acid-proof and fouling -free.

c). Heat Resistant:
Ceramic-lined composite steel pipe can work under circumstances of -50 to 800 degrees Celsius.

d). Lower Weight and Convenient Installation:
The ceramic-lined steel composite pipes are lighter than alloy pipes, cast iron pipes, and cast stone pipes and can be welded or connected through flanges, which reduces the expense of transportation and makes the pipes easier to install.
For the pipes with the same sizes, types and length, the weight of ceramic pipe is about 1/2 of the wearable cast alloy steel pipe’s, while the cost has reduced 10%~20% per meter. The weight of ceramic lined steel pipe is about 1/3 of the cast stone bent pipe’s, 1/2 of the cast stone straight pipe’s.

e). Lower Cost:
Ceramic-lined composite steel pipe can take place of expensive stainless steel, titanium, nickel, cast stone or alloy pipes. Extended service life can also reduce maintenance cost.

Features of Alumina Ceramic：

Alumina is a cost effective and widely used material in the family of engineered ceramics. Alumina ceramics have been developed and optimized for maximum wear resistance and corrosion resistance. A high density, diamond like hardness, fine grain structure and superior mechanical strength are the unique properties that make it the material of choice for a wide range of demanding applications. Ceramic has uses similar to Cast Basalt but it has greater resistance to wear in high velocity applications and impact resistance in extreme dynamic Systems