RustGuard^TM Bearing Developed For Better Rust Protection in Steel Mill Machinery

Special coating drastically improves rust resistance! - Extends service life 3.5 times!

NTN Corporation's RustGuard^TM offers improved rust resistance to bearings. Mainly intended for applications in steel mill machinery, this special coating process is applied over the entire surface of the inner and outer ring and rollers of the bearing. NTN has succeeded in boosting the bearing service life of this new product 3.5 times compared to conventional rust-resistant bearings.

Bearings used in steel machinery must often operate in harsh environments subject to large amounts of water (used in rolling, cooling and other processes) and slag (stony iron waste). In many cases these bearings have a short service life due to damage and wear compared to normal bearings. After investigating and analyzing many cases of product wear, NTN discovered that most wear is due to a so-called downtime-induced rust (^{note 1}). Factors in accelerating the spread of this rust are changes in the constituents of the metal rolling water (such as increased amounts of chlorine) and delayed bearing maintenance (dismantling and washing, repacking with grease, etc.)

This bearing benefits from the same special heat-treatment used for EA bearings (large-size bearings well known for their long service life in many applications) (^{note 2}). The entire surfaces of the inner and outer ring and rollers of the bearing are then subjected to a newly developed special manganese phosphate surface treatment. To determine the specifications needed for this coating, NTN succeeded in creating an experimental model of the conditions where this downtime-induced rust (^{note 1}) actually occurs, based on product breakdown data. NTN then developed a thick film coating effective in improving rust resistance and having a superb resistance to peeling, with minimum adverse effects on bearing fatigue life. More specifically, NTN succeeded in minimizing the increase in surface roughness of material during the film forming process to produce a more homogenous film with smaller particles. This coating is two to three times thicker than existing products.

The RustGuard^TM bearing delivers superior rust resistance with minimum adverse effect on bearing fatigue life, extending the bearing service life.

Features

- Long service life by boosting rust resistance

- Film coating 2 to 3 times thicker than conventional rust-resistant bearings, was achieved by developing a special manganese phosphate surface treatment

- Service life extended to 3.5 times longer than conventional rust-resistant products, in environments where downtime-induced rust occurs

Applications

Ideal for applications involving steel mill machinery and paper-making machinery subject to water spray or particles, etc.

Note 1: [Downtime-induced rust] : Rust is apparent on the raceway surfaces in a pattern that mirrors the pitch of the rolling elements. This type of rust occurs during equipment maintenance when a bearing is left for several hours in a static condition while moisture remains inside the bearing.

Note 2: [EA bearings]: Special heat treatment [carburizing & carbon-nitriding] for carburized steel used in large-size bearings. This heat-treatment process combines carburizing and nitriding to strengthen essential surface layer sections and drastically improve the bearing service life.

[Photo: bearing size: ID 245 × OD 345 × 310 width] weight 90.5 kilograms