SiC Composite Ceramic Liner and its Properties

Aug 02,2016

The main research and development personnel who is, in those days, the Bimetallic Technology (bimetallic barrel and bimetallic screw) Creator in China, nowadays the requirements to wear-resistant and corrosive-resistant heart parts from the field of plastic extrusion is higher and higher, the only application of bimetallic product reveals its deficiency. Further researching a new material which could be used for this special requirements from certain users becomes extremely indispensable. Then SiC composite ceramic plunges into the mind.

Left pictures show the newly-developed ceramic liners separately for single and twin screw extruders.

Composite Ceramic Liner and Its Properties                                               Compound Oval Liner

The Mechanical Properties of SiC Composite Ceramics is as below:
        Density ( ρ ):>3.04 g/cm3
        Normal Elastic Modulus ( Ε ):410 MPa
        Hardness ( HRC ): 89~92
        Buckling Strength ( σbb ): 380 MPa
        Pressive Strength ( σbc ): 3970 MPa
        Plane Strain Toughness ( Κic ):4 MPa/mm3/2
        Coefficient of Heat Expansion ( α1 ):4.0×10-6 / °F
        Thermal conductivity ( λ ):Φ30~35 W/(m•K)

Inoxidability under High Temperature: under a high temperature 1500℃, the reducing speed of metal weight is very slow.

SiC Composite Ceramics has a very excellent feature with resistance to frictional wear, this could not be compared by any other metal, even they are through more hardening way. Besides, the SiC Composite Ceramics also has a very excellent chemical stability, except the hydrofluoric acid, almost it has corrosion resistance to all other inorganic acid and lye, fusion alkali and salt, it even could bears a ultimate temperature up to 1500℃ in the air.

Because of the extruder screw is installed in a barrel as a cantilever, and is rotated inside the cylinder, both inter active surfaces touching or friction each other. It is unavoidable that there is a screw flight surface friction again st the cylinder inner surface, this is a “ Adhesive wear”, or could be named as the “contact wear”. The longer the screw L/D ratio, and the faster of the screw rotating speed, the serious the above wear. A large number of authoritative organizations "matching wear" test data shows that if the "wear and tear loss" coefficient to quantify the contact wear between the barrel and the screw, the figure below shows that as the segment barrel hole protection layer, the SiC ceramic material is working together with any screw metal material, such as the die steel D2 screw, high speed steel M2 screw, the "friction Vice" between materials, the Contact Wear performance is best.

Outside the SiC Composite Ceramic liner, there is a aluminum alloy protection coat(Sows below) which is our structural optimization measures we had got the patent protection in China, the advantage is as below:

1) SiC ceramic composite liner would work inside the a barrel, its linear expansion coefficient is much smaller than normal barrel metal material, due to this expansion coefficient difference, aluminum alloy coat plays a buffer role. When the barrel metal is heated, the expanding wouldn't make a tensile stress on the SiC ceramic liner directly. And when the barrel metal is cooling to room temperature, due to the compressive strength of SiC ceramic liner is far greater than coated pressure of the normal metal material, the liner will not be affected by stress and deformation, or to be cracked, or to be crushed;

2) Compared with the liner made from all the SiC composite ceramic material, aluminum alloy coating can significantly improve the Heat Transfer Efficiency when a ceramic liner inside a barrel; 

3) The positioning screw hole on the radial position could be made easily when a SiC composite ceramic liner inside the twin barrel; 

4) Compare with the liner made from all the SiC composite ceramic material, aluminum alloy coating can be reduced about 40% of the material cost and the manufacturing cost, brought the gospel to the extreme extrusion condition of the market by a big margin application. To compare with the foreign parallel products such as the ceramic barrel which is 10 times more expensive made of TOYO KOHAN in Japan, our SiC composite ceramic barrel is only about three times expensive and the service life is about five times than normal which was used in Foxconn Company in Shenzhen, enough to prove that our aluminum alloy coated SiC composite ceramic barrel is best cost-performance choice by uses; 

5) The aluminum alloy coated SiC ceramic liner made by our company, can help users to replace once the ceramic liner wear-off, simply and easily; 

6) This structural optimization can also protect the relatively expensive SiC composite ceramic liners safety in the making processing, transportation and installation process. 

We sincerely welcome any advice from users in the period of research and application of this new material. 

Chief Engineer Office / Shanghai Omega Machinery Co. Ltd

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