Patent Issued for Flash-Butt Welded Bearing Component
Resource from: 4 Traders Likes:249
Jul 24,2015
AKTIEBOLAGET SKF (Gothenburg, SE) has been issued patent number 9080608, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also AKTIEBOLAGET SKF).
The patent's inventors are Lund, Thore (Gothenburg, SE); Recina, Viktor (Torslanda, SE).
This patent was filed on May 27, 2011 and was published online on July 14, 2015.
From the background information supplied by the inventors, news correspondents obtained the following quote: "Flash-butt welding or 'flash welding' is a resistance welding technique for joining segments of metal rail, rod, chain or pipe in which the segments are aligned end to end and heated by electrical currents, producing an electric arc that melts and welds the ends of the segments, yielding an exceptionally strong and smooth joint.
"A flash butt welding circuit usually consists of a low-voltage, high-current energy source (usually a welding transformer) and two clamping electrodes. The two segments that are to be welded are clamped in the electrodes and brought together until they meet, making light contact. Energizing the transformer causes a high-density current to flow through the areas that are in contact with each other. Flashing starts, and the segments are forged together with sufficient force and speed to maintain a flashing action. After a heat gradient has been established on the two edges to be welded, an upset force is applied to complete the weld. This upset force extrudes slag, oxides and molten metal from the weld zone leaving a welding accretion in the colder zone of the heated metal. The joint is then allowed to cool slightly before the clamps are opened to release the welded article. The welding accretion may be left in place or removed by shearing while the welded article is still hot or by grinding, depending on the requirements.
"International publication no. WO 2006/103021 discloses a welded roller bearing ring made from a cold-rolled profile wire of roller bearing steel having a hypereutectic composition and a carbon content of at least 0.7%. The welded roller bearing ring comprises a soft-annealed coarse-grained nodular cementite joint obtained by butt welding. The region around the welded joint comprises a martensitic cementite structure with a higher carbide number and a finer structure relative to the remaining ring region. During the flash butt welding process, when two surfaces are forged together, a material flow perpendicular to the plane of the two surfaces is created. This material flow forms a grain structure or fibre flow oriented perpendicular to the plane of the two surfaces. Inclusions present within the material become incorporated in this material flow.
"In conventional bearing steels, the dominating inclusion type is sulphides due to the fact that the sulphur content normally is higher than the oxygen content. Since sulphides have an elongated shape they can become highly oriented during flash butt welding and thus make the steel anisotropic in the area of the weld joint. It has been found that the life time of a bearing component is most adversely affected by oxygen-containing inclusions, such as sulphide inclusions containing encapsulated or embedded oxide inclusions, since when such inclusions have matrix contact, they act as crack initiators. When a component such as a bearing ring is being flash butt welded, the resulting fibre flow carrying incorporated sulphides will therefore be unfavourable with respect to fatigue crack initiation and propagation in the finished welded bearing ring compared to a bearing that does not comprise a flash butt weld joint. In addition, the sulphides in bearing steels can be fully or partially dissolved in austenite in the weld zone. On cooling, the sulphides will preferentially precipitate at grain boundaries which will significantly weaken the weld zone.
"In order to avoid these problems with sulphides during flash butt welding it is not advantageous to reduce the sulphur content of the bearing steel to as close to zero as possible since this results in magnesium and calcium in the melt entering oxide inclusions in the form of aluminates and forming undesired complex aluminate inclusions. Pure aluminates are hard and brittle; they will break during hot forming and do not therefore pose a substantial problem to manufacturers of bearing components with high degrees of forming deformation. However, complex aluminates can be hard but they are not brittle so they will remain intact during rolling and will therefore be incorporated into the finished bearing component. If a complex aluminate inclusion becomes located in an area of the bearing component subject to heavy loading, this is where a fatigue failure will start."
Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "An object of the invention is to provide a bearing component comprising at least one flash butt weld joint which has improved fatigue properties.
"The object of the invention is achieved by a bearing component comprising steel that contains, by weight, max 20 ppm S and max 15 ppm O and includes sulphide inclusions whereby less than 5% of the sulphide inclusions contain encapsulated or embedded oxide inclusions.
"It has been found that the adverse effects of the unfavourable fibre flow that flash butt welding creates may be limited by manufacturing bearing components that are to be flash butt welded out of such steel. Using such a clean steel namely provides a welded bearing component having a superior weld joint since the welded bearing component does not contain areas of structural weakness as might otherwise occur. Such a welded bearing component therefore has a high degree of structural integrity compared to flash butt welded bearing ring that does not comprise such steel.
"According to another embodiment of the invention the steel comprises max 10 ppm O or max 8 ppm O.
"According to an embodiment of the invention the steel contains between 0.10 to 1.20 weight-% C. According to another embodiment of the invention the steel contains between 0.15 to 0.40 weight-% C. The steel may for example be of ASTM A295 / A295M-09 type, such ISO 683-17:1999 ASTM A-295-98, or any other high-carbon through-hardened steel that is suitable for an application in which it is subjected to alternating Hertzian stresses, such as rolling contact or combined rolling and sliding.
"According to another embodiment of the invention the steel comprises an element selected from the group: Ca, Mg, Te or a lanthanide, such as Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu. According to a further embodiment of the invention the steel comprises, by weight, 10-30 ppm of an element selected from the group above.
"The addition of such an element to bearing steel (i.e. steel suitable for use in a bearing component) after the sulphur content has been reduced to a level substantially of the same order as the oxygen content, will reduce the total number of sulphide inclusions remaining in the steel and/or it will modify the shape of the remaining inclusions into one that is less detrimental to mechanical properties in the final bearing component, (tellurium for example spherodizes the sulphide inclusions). It has namely been found that the addition of such an element to bearing steel will result in less than 5% of the sulphide inclusions containing encapsulated or embedded oxide inclusions. The addition of such an element will also result in all of the sulphide inclusions having an aspect ratio of less than 3:1 (i.e. the ratio of the inclusion's largest diameter to the inclusion's shortest diameter) and in the maximum sulphide inclusion length being 125.mu.m (micrometers) at a Reduced Variate equal to 3 evaluated using the ASTM E2283-03 Extreme Value Analysis Standard. Such sulphide inclusions are less damaging to a bearing component as regards its fatigue properties. Furthermore, the absence of sulphide inclusions having an aspect ratio greater than 3:1 and having a maximum length greater than 125 .mu.m (micrometers) gives the steel more uniform properties in all directions and thereby reduces directional anisotropy in the steel.
"According to an embodiment of the invention the bearing component constitutes at least part of one of the following: a ball bearing, a roller bearing, a needle bearing, a tapered roller bearing, a spherical roller bearing, a toroidal roller bearing, a ball thrust bearing, a roller thrust bearing, a tapered roller thrust bearing, a wheel bearing, a hub bearing unit, a slewing bearing, a ball screw, or a component for an application in which is subjected to alternating Hertzian stresses, such as rolling contact or combined rolling and sliding.
"According to another embodiment of the invention the bearing component constitutes a bearing ring or a bearing ring segment, two or more of which may be welded into a bearing ring."
For the URL and additional information on this patent, see: Lund, Thore; Recina, Viktor. Flash-Butt Welded Bearing Component. U.S. Patent Number 9080608, filed May 27, 2011, and published online on July 14, 2015.
(4 Traders)
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1.The news above mentioned with detailed source are from internet.We are trying our best to assure they are accurate ,timely and safe so as to let bearing users and sellers read more related info.However, it doesn't mean we agree with any point of view referred in above contents and we are not responsible for the authenticity. If you want to publish the news,please note the source and you will be legally responsible for the news published.
2.All news edited and translated by us are specially noted the source"CBCC".
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