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KS R21

Product catalog summary

Overview of KS R21 Material:
KS R21 is a lead-free steel-aluminum composite material used for main bearings in gasoline and diesel engines. It offers improved load carrying capacity compared to KS R20, while maintaining good embedding capability and adaptability. The material is resistant to oil corrosion and complies with the EU Directive 2000/53/EC on End-of-Life Vehicles.

Bearing Structure:
The KS R21 bearings consist of a steel back, an intermediate layer of pure aluminum, and an aluminum-tin-copper running layer. The steel back is typically grade DC04 with a hardness of 150-220 HB, and its thickness ranges from 1.0 to 3.0 mm. The intermediate aluminum layer is 0.01 to 0.05 mm thick, while the running layer is 0.2 to 0.5 mm thick with a hardness of 40-60 HB.

Material Characteristics:
Key properties include a tensile strength of over 165 MPa, a yield point of over 140 MPa, a Young's modulus of 63 GPa, a coefficient of thermal expansion of 24 x 10^-6 k^-1, and thermal conductivity of 50 W/(m·k).

Manufacturing Process:
The aluminum alloy is produced through vertical continuous casting, followed by mechanical processing and heat treatment. A pure aluminum foil is plated onto the strand, and roll cladding applies this pre-composite onto the steel. Thermomechanical treatments finalize the material characteristics.

Application and Performance:
KS R21 is suitable for medium-load engines due to its excellent anti-seizure properties, good embedding capability, adaptability, and improved wear resistance compared to KS R20. The running layer's chemical composition includes 16.5 to 22.5% Sn, 0.7 to 1.3% Cu, and other elements in smaller quantities.

Comparison and Testing:
KS R21 demonstrates a specific load carrying capacity of up to 55 MPa. Test conditions included a bearing shell diameter of 47.8 mm, wall thickness of approximately 1.4 mm, sliding velocity of 0.25 m/sec, and a static load of 6.2 MPa over a 3-hour duration. The material shows superior wear behavior compared to other materials like KS R20, KS R25, KS R30, and KS R45.

Disclaimer:
KS Gleitlager GmbH does not guarantee the completeness of the data and advises customers to assess the material's suitability for their specific applications.

Catalog excerpts

Kolbenschmidt Pierburg Group KS R21 Lead-free Steel-Aluminum Composite Material for Main Bearings

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Brief description of the sliding material Plain bearings made from steel/aluminum composite materials are widely used as main bearings in gasoline and diesel engines. KS R21 is a robust bearing material. Compared to KS R20 this material has an improved load carrying capacity without losing the other characteristics, like good embedding capability and adaptability. Due to this characteristics bearing shells and thrust washers can be used in bi-material designs. KS R21 is insensitive to oil corrosion. With its specific load carrying capacity up to 55 MPa, this material is suited for application...

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Chemical composition of the running layer Sn Cu Si Ti Ni Fe Mn others combined AI The hardness of the running layer is in the range of 40 - 60 HB Manufacture of the sliding material The aluminum alloy is manufactured in vertical continuous casting. Mechanical processing of the strand surface as well as the specific heat treatment steps prepare the material for plating. The so-called pre-composite results from plating a pure aluminum foil (Al 99.5) on the strand. Roll cladding is used to apply the pre-composite onto the steel. Selective thermomechanical treatment steps give the desired material...

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KS Gleitlager GmbH · Am Bahnhof 14 · 68789 St. Leon-Rot · GERMANY Tel. +49 6227 56-0 · Fax +49 6227 56-302 · www.kspg.com KS Gleitlager GmbH does not assume any liability for the completeness of the data presented in this materials brochure. It is exclusively up to the customer to form his opinion about the characteristics of the material and its adequacy for the purposes intended by the customer. KS Gleitlager GmbH would also like to stress that any information given in this materials brochure does not constitute a legal guarantee for the appearance, characteristics and workmanship nor does...

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