METHOD FOR IMPROVING THE PROPERTIES OF RAILWAY WHEELS AND RAILWAY WHEEL

Abstract: The present invention relates to a railway wheel and a method for improving the properties of railway wheels (1). According to this method portions of the base material (2) of the railway wheel (1) are removed and replaced by completing surface layers (16, 17) which are provided by forming a melt on said portions of the base material (2), preferably by laser radiation, and by adding additive to said melt for imparting additional properties to the completing surface layers (16, 17) besides the properties imparted thereto by the base material (2).

Description: Method for improving the properties of railway wheels and railway wheel. The present invention relates to a method for improving the properties of railway wheels. The invention also relates to a railway wheel. Heavy demands are made upon railway wheels because the trains are driven at higher and higher speeds and the wheels thereby roll faster and faster, the trains are loaded with ever increasing loads and air and rain pollutions expose the wheels to ever increasing corrosive attacks . The object of the present invention is to provide a method which improves the properties of railway wheels regarding inter alia surface fatigue and when they are brought to high rolling speeds and heavy loads and when they are exposed to air and rain pollutions. This is arri- ved at according to the invention by providing the initially defined method with the characterizing steps primarily of subsequent claim 1. Since the railway wheels have been manufactured in accordance with said characterizing steps, the good pro- perties of their well-tried base material are utilized while at the same time the properties regarding surface fatigue and in preventing crack formation, ovality and corrosive attacks are improved in comparison with said base material . The problem upon which the invention is based is solved also by means of a railway wheel having the characterizing features of subsequent claim 20. The invention will be further described below with reference to the accompanying drawings, in which fig. 1 is a perspective view of a part of a railway wheel from which base material portions which might crack or have cracked have been removed by turning; fig. 2 is the same view of the railway wheel as in fig. 1, said wheel being completed with surface layers ; fig. 3 is the same view of the railway wheel as in fig. 1, said wheel being completed with a surface layer having another location than in fig. 2; fig. 4 is the same view of the railway wheel as in fig. 1, said wheel being completed with a surface layer having another location than in fig. 2 and 3; and fig. 5 is a section through the railway wheel of fig. 1 during application of a completing surface layer. A part of a railway wheel 1 which shall be completed with a surface layer is shown in the drawings. The illustrated railway wheel 1 is made of a base material 2, e.g. steel, and is provided with a wheel tread surface 3 and a wheel flange 4. In fig. 1 reference numerals 5 and 6 refer to those portions of the tread surface 3 which are subjected to high stresses when the railway wheel 1 rolls on the rail. Said portions 5, 6 may e.g. consist of such portions of the tread surface which have cracks or are expected to crack due to fatigue of the base material 2, e.g. if the railway wheel 1 is used on high-velocity trains. In order to improve the properties of the railway wheel 1, a surface layer 7 and 8 of the base material 2 is removed within said portions 5 and 6. This can be done by removing said surface layers 7 , 8 by turning or grinding or in any other way. The railway wheel 1 may e.g. for this purpose be placed in a rotary device (not shown) for rotation relative to a surface layer processing or machining device, e.g. a turning chisel (not shown). By removing the surface layers 7, 8 of the base material 2, peripheral, annular recesses 9, 10 are formed in the railway wheel 1. Thereafter, the railway wheel 1 can be placed in another rotary device (not shown) for rotation relative to an assembly 11. This assembly 11 is adapted to subject the base material 2 at the recesses 9, 10 to heat radiation, preferably to high-energy radiation in the form of laser radiation 12, for melting said base material 2 in the bottom of the recesses 9, 10. The assembly 11 is adapted, while said base material 2 is brought to melt, to simultaneously add to the melt 13 one or more additives 14, 15 of such type that when the melt 13 has cooled, completing surface layers 16, 17 are formed, having other properties than the base material 2. This melting and addition of material is carried through such that the completing surface layers 16, 17 are formed of elongated strings 18 which are made by forming said melt 13 and letting it solidify. The strings 18 can be located so close to each other that they partly overlap each other (as is shown in fig. 2 and 4) or be located spaced from each other such that the railway wheel 1 in the spaces 19 therebetween has an outer surface 20 of base material 2. As an example, one completing surface layer 16 can be located on the wheel tread surface 3 close to inner portions of the railway wheel 1 and the other completing surface layer 17 close to the wheel flange 4. Furthermore, the width A of the completing surface layer 16 can be chosen such that said width corresponds to about one third of the total width B of the tread surface 3 , and the width C of the completing surface layer 17 can be chosen such that this width is less than said width A. The completing surface layers 16, 17 can be located at such distance from each other that a space 21 is defined therebetween having an outer surface 20 of base material 2 and this space 21 can be chosen to have a width D which is somewhat less than the width A of the completing surface layer 16. The strings 18 can be located such that they extend around the railway wheel 1 (as is shown in fig. 2 or 3 ) or such that they run obliquely relative to the axis of the railway wheel 1 and define an angle 0C of 20 - 90° with said axis (the direction of which is marked with A in fig. 4) . Additive or additives 14, 15 is/are added to the melt 13 such that the completing surface layer or layers 16, 17 provide for, inter alia, a) improved resistance to crack formation compared to the base material 2 and/or b) improved resistance to surface fatigue compared to the base material 2 and/or c) improved properties regarding the preservation of the circular shape of the wheel tread surface 3 compared to the base material 2 and/or d) improved resistance to corrosion in comparison with if the railway wheel 1 is made only of the base material 2. Such an additive or additives 14, 15 can also be added to the melt 13 that the completing surface layers 16, 17 get electrically conducting properties for obtaining at least a certain electric contact between the railway wheel 1 and a rail in contact therewith, through said completing surface layers 16, 17 even if this electric contact is not as good as the electric contact obtainable with the base material 2. The completing surface layers 16, 17 can be located so that the outer surfaces 20 of the base material 2 can get in contact with the rail for providing electric contact between the base material 2 and said rail . Furthermore, the completing surface layers 16, 17 can be located so that the outer surfaces 20 of the base material 2 on at least one of the railway wheels 1 on a railway- waggon will engage the rail when said waggon is driven thereon, so that there will always be electric contact between at least one of the railway wheels 1 and the rail. The additive 14, 15 is chosen preferably also with regard to the type of base material 2 for the railway wheel 1 and/or the extent of improvement of said properties you desire. Thus, the additive 14, 15 can be a metal, a metal alloy or a metal mixture and/or at least a ceramic. Said metallic material 14 can be e.g. iron, cobalt or nickel and said ceramics 15 can be e.g. tungsten, carbide, titanium carbide, vanadium, niobium carbide or tantalum carbide. The inventive method and inventive object is not limited to what is described above and shown in the drawings, but may vary within the scope of the following claims. As alternatives not described in detail, one can mention that one or more completing surface layers 16, 17 can be provided on the wheel flange 4, that the railway wheel 1 can be provided with one or more completing surface layers 16, 17 on the wheel flange 4, that said recesses 9, 10 preferably can be filled with completing sur- face layers 16, 17 so that the outer surfaces 22 thereof, eventually after a smoothing surface treatment such as grinding, will be flush with the outer surfaces 20 of adjoining base material 2 and that the portions of the railway wheel 1 to be provided with completing surface layers 16, 17 are preheated.

Claims: Claims : 1. Method for improving the properties of railway wheels, c h a r a c t e r i z e d b y a) removing at least a surface layer of the base material from such portions (5 and/or 6) of the railway wheel (1) which have cracks or are expected to crack due to exposure to loads of the railway wheel (1) during use thereof, e.g. when said railway wheel (1) is brought to high rolling speeds during use on high-velocity trains, b) melting the base material in the recess or reces- ses formed by the removal of said base material, by heat radiation, preferably laser radiation, c) adding additive to the melt of said base material in the recess or recesses in order to impart to the railway wheel additional properties besides the properties given thereto by the base material. 2. Method according to claim 1, c h a r a c t e r i z e d b y removing, preferably by turning or grinding, said surface layer (7 and/or 8) of the base material (2) by rotating the railway wheel (1) relative to a surface layer processing or machining device, whereby one or more peripheral annular recesses (9 and/or 10) are formed in the railway wheel (1) , locating at least one completing surface layer (16 and/or 17) in the recess or recesses (9 and/or 10) formed by the removal of the surface layer (7 and/or 8) of the base material (2) and providing said completing surface layer (16 and/or 17) by rotating the railway wheel (1) relative to an assembly (11) which through heat radiation, preferably laser radiation (12), can melt the base material (2) of the railway wheel (1) and which at the same time can add said additive (14 and/or 15) to the melt (13) . 3. Method according to claim 1 or 2 , c h a r a c t e r i z e d b y melting the base material (2) of the railway wheel (1) at the bottom of the recess or recesses (9 and/or 10) . 4. Method according to any preceding claim, c h a r a c t e r i z e d b y filling said recess or recesses (9 and/or 10) with the completing surface layer (16 and/or 17) such that the outer surface (22) of said comp- leting surface layer (16 and/or 17) , eventually after a smoothing surface treatment thereof, will be flush with the outer surface (20) of adjoining base material (2) of the railway wheel (1) . 5. Method according to any preceding claim, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of elongated strings (18) which extend around the railway wheel (1) and which are made by forming said melt (13) and letting it solidify. 6. Method according to any of claims 1-4, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which run obliquely relative to an axis (A) of the railway wheel (1) such that they define an angle (Ct) of 20 - 90° with said axis (A) . 7. Method according to any preceding claim, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which are located so close to each other that they partly overlap each other. 8. Method according to any of claims 1-6, c h a r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which are spaced from each other such that in the spaces (19) between said strings (18) there is an outer surface (20) of base material (2) . 9. Method according to any preceding claim, c h a - r a c t e r i z e d b y providing one or more completing surface layers (16 and/or 17) on the wheel tread surface (3) of the railway wheel (1) . 10. Method according to claim 9, c h a r a c t e r i z e d b y providing at least two completing surface layers (16, 17) on the wheel tread surface (3) of the railway wheel (1) of which one completing surface layer (16) is located closest to inner portions of the railway wheel and the other completing surface layer (17) closest to the wheel flange (4) of said railway wheel (1) . 11. Method according to claim 10, c h a r a c t e r i z e d b y choosing the width (A) of the completing surface layer (16) closest to the inner portions of the railway wheel (1) such that said width corresponds to about one third of the total width (B) of the wheel tread surface (3), and choosing the width (C) of the completing surface layer (17) closest to the wheel flange (4) such that this width is less than said width (A) of the completing surface layer (16) located within said latter completing surface layer (17). 12. Method according to claim 10 or 11, c h a r a c t e r i z e d b y locating the completing surface layers (16, 17) at a distance from each other such that a space (21) is defined therebetween having an outer surface (20) of base material (2), and choosing the width (D) of said space (21) preferably so that said width is somewhat less than the width of the widest completing surface layer (16 or 17) . 13. Method according to any preceding claim, c h a r a c t e r i z e d b y adding to said melt such an additive or additives (14 and/or 15) that the completing surface layer (16 and/or 17) provide for that the rail- way wheel (1) attains a) improved resistance to crack formation compared to the base material (2) and/or b) improved resistance to surface fatigue compared to the base material (2) and/or c) improved properties regarding the preservation of the circular shape of the wheel tread surface (3) compared to the base material (2) and/or d) improved resistance to corrosion. 14. Method according to any preceding claim, c h a - r a c t e r i z e d b y adding such an additive or additives (14 and/or 15) to the melt (13) that the completing surface layer (16 and/or 17) gets electrically conducting properties for obtaining at least a certain electric contact between the railway wheel (1) and a rail in contact therewith, through said completing surface layers (16 and/or 17) . 15. Method according to any preceding claim, c h a r a c t e r i z e d b y locating the completing surface layer (16 and/or 17) on the railway wheel (1) so that outer surfaces (20) of the base material (2) of said railway wheel (1) can get in contact with the rail for provi- ding electric contact between the base material (2) and the rail in contact therewith. 16. Method according to any preceding claim, c h a r a c t e r i z e d b y locating the completing surface layer (16 and/or 17) on the railway wheel (1) so that outer surfaces (20) of the base material (2) on at least one of the railway wheels (1) on a railway waggon will engage the rail when said waggon is driven thereon, so that there will always be electric contact between at least one of the railway wheels (1) on a railway waggon and the rail during driving of said waggon. 17. Method according to any preceding claim, c h a r a c t e r i z e d b y adding to said melt (13) additive (14 and/or 15) in the form of at least a metal, metal alloy or mixture of metals (14) and/or at least a ceramic (15) . 18. Method according to claim 17, c h a r a c t e r i z e d b y adding to said melt (13) metallic material in the form of iron, cobalt or nickel. 19. Method according to claim 17 or 18, c h a r a c - t e r i z e d b y adding to said melt (13) ceramics (15) in the form of tungsten carbide, titanium carbide, vanadium, niobium carbide or tantalum carbide. 20. Railway wheel comprising a base material (2) and of which portions (5 and/or 6) are subjected to tendencies to crack formation, c h a r a c t e r i z e d i n that said portions (5 and/or 6), which are subjected to tendencies to crack formation, includes at least one recess (9 and/or 10) , that at least one completing surface layer (16 and/ /or 17) is provided in said recess (9 and/or 10) , and that said completing surface layer (16 and/or 17) consists of base material (2) and additive (14 and/or 15), whereby the base material (2) is melted by heat radiation, preferably laser radiation, while at the same time adding the additive (14 and/or 15) to the melt (13) for imparting to the railway wheel (1) additional properties besides the properties the base material (2) can give thereto. 21. Railway wheel according to claim 20, c h a r a c t e r i z e d i n that said melt (13) includes such an additive or additives (14 and/or 15) that the completing surface layer (16 and/or 17) provide for that the railway wheel (1) attains a) improved resistance to crack formation compared to the base material (2) and/or b) improved resistance to surface fatigue compared to the base material (2) and/or c) improved properties regarding the preservation of the circular shape of the wheel tread surface (3) compared to the base material (2) and/or d) improved resistance to corrosion. 22. Railway wheel according to claim 20, c h a r a c t e r i z e d i n that the completing surface layer (16 and/or 17) is provided on such portions (5 and/ /or 6) of the base material (2) which have cracks or are expected to crack due to loading of the railway wheel (1) during use thereof, preferably when it is used on high- -velocity trains during driving at high speeds, and that said completing surface layer (16 and/or 17) has an improved resistance to crack formation compared to the base material (2) . 23. Railway wheel according to claim 22, c h a r a c t e r i z e d i n that said completing surface layer or layers (16 and/or 17) is/are provided in at least one recess (9 and/or 10) in the railway wheel (1) , said recess (9 and/or 10) being defined by removal of surface layers (7 and/or 8) of the base material (2) which have cracks or are expected to crack. 24. Railway wheel according to any of claims 20-23, c h a r a c t e r i z e d i n that said completing surface layer or layers (16 and/or 17) is/are provided in said recess or recesses (9 and/or 10) with an outer surface (22) thereof located flush with or substantially flush with an outer surface (20) of adjoining base material (2) . 25. Railway wheel according to any of claims 20-24, c h a r a c t e r i z e d i n that at least one completing surface layer (16 and/or 17) is provided on the rail- way wheel (1) such that at least one of the railway wheels (1) on a railway waggon will engage the rail with its base material (2) when said waggon is driven thereon, so that it thereby will always be electric contact between the railway waggon and the rail through the base material (2) in at least one of the railway wheels (1) . AMENDED CLAIMS [received by the International Bureau on 25 August (25.08.98); original claims 1-25 replaced by amended claims 1-23 (6 pages)] 1. Method for improving the properties of railway wheels, c h a r a c t e r i z e d b y a) removing at least a surface layer of the base material from such portions (5 and/or 6) of the railway wheel (1) which have cracks or are expected to crack due to exposure to loads of the railway wheel (1) during use thereof, e.g. when said railway wheel (1) is brought to high rolling speeds during use on high-velocity trains, b) melting the base material in the recess or reces- ses formed by the removal of said base material, by heat radiation, preferably laser radiation, c) adding additive to the melt of said base material in the recess or recesses in order to impart to the railway wheel additional properties besides the properties given thereto by the base material, d) locating strings (18) of said additive beside each other in the recess or recesses until said recess or recesses are filled, and e) surface treating a completing surface layer (16 and/or 17) formed in the recess or recesses by said strings located beside each other, such that the surface thereof will be flush with an outer surface (20) of adjoining base material (2) . 2. Method according to claim 1, c h a r a c t e r i - z e d b y removing, preferably by turning or grinding, said surface layer (7 and/or 8) of the base material (2) by rotating the railway wheel (1) relative to a surface layer processing or machining device, whereby one or more peripheral annular recesses (9 and/or 10) are formed in the railway wheel (1) , locating at least one completing surface layer (16 and/or 17) in the recess or recesses (9 and/or 10) formed by the removal of the surface layer (7 and/or 8) of the base material (2) and providing said completing surface layer (16 and/or 17) by rotating the rail- way wheel (1) relative to an assembly (11) which through heat radiation, preferably laser radiation (12) , can melt the base material (2) of the railway wheel (1) and which at the same time can add said additive (14 and/or 15) to the melt (13) . 3. Method according to claim 1 or 2 , c h a r a c t e r i z e d b y melting the base material (2) of the railway wheel (1) at the bottom of the recess or recesses (9 and/or 10) . 4. Method according to any preceding claim, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of elongated strings (18) which extend around the railway wheel (1) and which are made by forming said melt (13) and letting it solidify. 5. Method according to any of claims 1-3, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which run obliquely relative to an axis (A) of the railway wheel (1) such that they define an angle (O) of 20 - 90° with said axis (A) . 6. Method according to any preceding claim, c h a - r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which are located so close to each other that they partly overlap each other. 7. Method according to any of claims 1-5, c h a r a c t e r i z e d b y forming the completing surface layer (16 and/or 17) of strings (18) which are spaced from each other such that in the spaces (19) between said strings (18) there is an outer surface (20) of base material (2). 8. Method according to any preceding claim, c h a - r a c t e r i z e d b y providing one or more completing surface layers (16 and/or 17) on the wheel tread surface (3) of the railway wheel (1) . 9. Method according to claim 8, c h a r a c t e r i z e d b y providing at least two completing surface layers (16, 17) on the wheel tread surface (3) of the railway wheel (1) of which one completing surface layer (16 ) is located closest to inner portions of the railway wheel and the other completing surface layer (17) closest to the wheel flange (4) of said railway wheel (1) . 10. Method according to claim 9, c h a r a c t e r i z e d b y choosing the width (A) of the completing surface layer (16) closest to the inner portions of the railway wheel (1) such that said width corresponds to about one third of the total width (B) of the wheel tread surface (3), and choosing the width (C) of the completing surface layer (17) closest to the wheel flange (4) such that this width is less than said width (A) of the completing surface layer (16) located within said latter completing surface layer (17). 11. Method according to claim 9 or 10, c h a r a c t e r i z e d b y locating the completing surface layers (16, 17) at a distance from each other such that a space (21) is defined therebetween having an outer surface (20) of base material (2) , and choosing the width (D) of said space (21) preferably so that said width is somewhat less than the width of the widest completing surface layer (16 or 17) . 12. Method according to any preceding claim, c h a r a c t e r i z e d b y adding to said melt such an additive or additives (14 and/or 15) that the completing surface layer (16 and/or 17) provide for that the rail- way wheel (1) attains a) improved resistance to crack formation compared to the base material (2) and/or b) improved resistance to surface fatigue compared to the base material (2) and/or c) improved properties regarding the preservation of the circular shape of the wheel tread surface (3) compared to the base material (2) and/or d) improved resistance to corrosion. 13. Method according to any preceding claim, c h a - r a c t e r i z e d b y adding such an additive or additives (14 and/or 15) to the melt (13) that the completing surface layer (16 and/or 17) gets electrically conducting properties for obtaining at least a certain electric contact between the railway wheel (1) and a rail in contact therewith, through said completing surface layers (16 and/or 17) . 1 . Method according to any preceding claim, c h a r a c t e r i z e d b y locating the completing surface layer (16 and/or 17) on the railway wheel (1) so that outer surfaces (20) of the base material (2) of said railway wheel (1) can get in contact with the rail for provi- ding electric contact between the base material (2) and the rail in contact therewith. 15. Method according to any preceding claim, c h a r a c t e r i z e d b y locating the completing surface layer (16 and/or 17) on the railway wheel (1) so that outer surfaces (20) of the base material (2) on at least one of the railway wheels (1) on a railway waggon will engage the rail when said waggon is driven thereon, so that there will always be electric contact between at least one of the railway wheels (1) on a railway waggon and the rail during driving of said waggon. 16. Method according to any preceding claim, c h a r a c t e r i z e d b y adding to said melt (13) additive (14 and/or 15) in the form of at least a metal, metal alloy or mixture of metals (14) and/or at least a ceramic (15). 17. Method according to claim 16, c h a r a c t e r i z e d b y adding to said melt (13) metallic material in the form of iron, cobalt or nickel. 18. Method according to claim 16 or 17, c h a r a c - t e r i z e d b y adding to said melt (13) ceramics (15) in the form of tungsten carbide, titanium carbide, vanadium, niobium carbide or tantalum carbide. 19. Railway wheel comprising a base material (2) and of which portions (5 and/or 6) are subjected to tendencies to crack formation, c h a r a c t e r i z e d i n that said portions (5 and/or 6), which are subjected to tendencies to crack formation, includes at least one recess (9 and/or 10) , that at least one completing surface layer (16 and/ /or 17) is provided in said recess (9 and/or 10), that said completing surface layer (16 and/or 17) consists of base material (2) and additive (14 and/or 15), whereby the base material (2) is melted by heat radiation, preferably laser radiation, while at the same time adding the additive (14 and/or 15) to the melt (13) for imparting to the railway wheel (1) additional properties besides the properties the base material (2) can give thereto, that said completing surface layer (16 and/or 17) consists of a number of strings (18) which are located beside each other in said recess (9 and/or 10) such that said strings fill said recess, and that the surface of said completing surface layer (16 and/or 17) by means of a surface treatment is brought to be flush with an outer surface (20) of adjoining base material (2) . 20. Railway wheel according to claim 19, c h a r a c t e r i z e d i n that said melt (13) includes such an additive or additives (14 and/or 15) that the completing surface layer (16 and/or 17) provide for that the railway wheel (1) attains a) improved resistance to crack formation compared to the base material (2) and/or b) improved resistance to surface fatigue compared to the base material (2) and/or c) improved properties regarding the preservation of the circular shape of the wheel tread surface (3) compared to the base material (2) and/or d) improved resistance to corrosion. 21. Railway wheel according to claim 19, c h a r a c t e r i z e d i n that the completing surface layer (16 and/or 17) is provided on such portions (5 and/ /or 6) of the base material (2) which have cracks or are expected to crack due to loading of the railway wheel (1 ) during use thereof, preferably when it is used on high- -velocity trains during driving at high speeds, and that said completing surface layer (16 and/or 17) has an improved resistance to crack formation compared to the base material (2) . 22. Railway wheel according to claim 21, c h a r a c t e r i z e d i n that said completing surface layer or layers (16 and/or 17) is/are provided in at least one recess (9 and/or 10) in the railway wheel (1), said recess (9 and/or 10) being defined by removal of surface layers (7 and/or 8) of the base material (2) which have cracks or are expected to crack. 23. Railway wheel according to any of claims 19-22, c h a r a c t e r i z e d i n that at least one comple- ting surface layer (16 and/or 17) is provided on the railway wheel (1) such that at least one of the railway wheels (1) on a railway waggon will engage the rail with its base material (2) when said waggon is driven thereon, so that it thereby will always be electric contact between the railway waggon and the rail through the base material (2) in at least one of the railway wheels (1) . MEWED SHEET (ARTICLE 19)

Inventors: OLOFSSON JOHAN LENNART, OLOFSSON, JOHAN, LENNART
Applicants: DUROC AB, OLOFSSON JOHAN LENNART, OLOFSSON, JOHAN, LENNART
Application year: 1998
Main classification: B60B17
IPC codes: B23K35, B23P6, B60B17, C21D1, C21D9