Wear-resistant roller
The invention relates to a wear-resistant roller for crushing of particulate material, such as crude ore for use in the cement or minerals industry comprising a roller body, a wear surface on the roller body. The wear surface comprises welding beads comprising a primary fraction of carbide material and a secondary fraction of material selected from the group consisting of Nickel, Nickel alloys, mixtures of Nickel and Nickel alloys and mixtures of Nickel containing refractory hard materials, Cobalt, Cobalt alloys, mixtures of Cobalt and Cobalt alloys and mixtures of Cobalt containing refractory hard materials. Furthermore, the welding beads are welded to the roller body in an overlapping manner such that two neighbouring welding beads comprise an overlapping volume and a non-overlapping volume, the overlapping volume being an intersection volume between the two neighbouring overlapping welding beads, and the fraction of carbide material being higher in the overlapping volume than in the non-overlapping volume such that the overlapping volume has a higher wear resistance compared to the non-overlapping volume having a lower wear-resistance. Also the invention relates to a method of forming such a wear surface on a roller body.
1. A wear-resistant roller for crushing of particulate material, for use in the cement or minerals industry comprising:
a roller body,
a wear surface on the roller body,
the wear surface comprising welding beads comprising a primary fraction of carbide material and a secondary fraction of material selected from the group consisting of nickel, nickel alloys, mixtures of nickel and nickel alloys and mixtures of nickel containing refractory hard materials, cobalt, cobalt alloys, mixtures of cobalt and cobalt alloys and mixtures of cobalt containing refractory hard materials,
the welding beads being welded to the roller body in an overlapping manner such that two neighbouring welding beads comprise an overlapping volume and a non-overlapping volume, and
the overlapping volume having a higher wear resistance compared to the non-overlapping volume having a lower wear-resistance.
2. A wear-resistant roller according to claim 1 , wherein the welding beads are plasma transfer arc welding beads and wherein the primary fraction of carbide material comprises 40-70% of tungsten carbides and wherein the secondary fraction of material comprises 30-50% of material selected from the group consisting of nickel, nickel alloys, mixtures of nickel and nickel alloys and mixtures of nickel containing refractory hard materials, cobalt, cobalt alloys, mixtures of cobalt and cobalt alloys and mixtures of cobalt containing refractory hard materials.
3. A wear-resistant roller according to claim 1 , wherein the wear surface has a pre-wear wear surface profile with overlapping volumes having an overlap height and non-overlapping volumes having a non-overlap height, the non-overlap height being higher than the overlap height in the pre-wear wear surface profile, and a post-wear wear surface profile, wherein the overlap height is higher than the non-overlap height.
4. A wear-resistant roller according to claim 3 , wherein a difference between the overlapping height and the non-overlapping height in the post-wear profile together with an intermediate distance between two neighbouring overlapping volumes defines a recess for retention of particulate material defining an autogenous wear layer protecting the non-overlapping volumes from further wear.
5. A wear-resistant roller according to claim 4 , wherein the intermediate distance between two neighbouring overlapping volumes is tailored to ensure retention of an autogenous wear layer for a certain type of crushed mineral feed.
6. A wear-resistant roller according to claim 4 , wherein the intermediate distance between two neighbouring overlapping volumes is 10 to 20 mm to ensure retention of an autogenous wear layer of grinded grey cement clinker.
7. A wear-resistant roller according to claim 1 , wherein the wear surface comprises a series of circumferential welding beads wherein neighbouring circumferential welding beads are overlapping neighbouring circumferential welding beads thus defining circumferential overlapping volumes such that the extension of the overlapping volumes substantially follows the circumferential direction of the wear-resistant roller.
8. A wear-resistant roller according to claim 1 , wherein the welding beads have a linear shape, a sinusoidal shape, a zigzag shape or a step-function shape in the circumferential direction.
9. A wear-resistant roller according to claim 8 , wherein the overlapping volume has a linear shape in the circumferential direction.
10. A wear-resistant roller according to claim 1 , wherein the overlapping volume has a sinusoidal shape, a zigzag shape or a step-function shape in the circumferential direction.
11. A wear-resistant roller according to claim 1 , wherein the welding beads have a width of approximately 8 mm to 24 mm.
12. A wear-resistant roller according to claim 1 , wherein the overlapping volume has a width of approximately 0.5 mm to 8 mm.
13. A roller mill comprising:
a feed of material,
at least one wear-resistant roller according to claim 1 for comminution of the feed of material, and
the mill being a roller press or a vertical mill.
14. A method of forming a wear surface on a roller body, the method comprising the steps of:
welding a first welding head comprising a primary fraction of carbide material and a secondary fraction of material selected from the group consisting of nickel, nickel alloys, mixtures of nickel and nickel alloys and mixtures of nickel containing refractory hard materials, cobalt, cobalt alloys, mixtures of cobalt and cobalt alloys and mixtures of cobalt containing refractory hard materials onto a roller body,
welding a second welding bead partially overlapping the first welding bead thereby re-heating an overlapping volume of the first welding bead.
15. A method of forming a wear surface on a roller body according to claim 14 , wherein a series of welding beads are welded side-by-side, each welding bead partially overlapping neighbouring welding beads.
16. A method of forming a wear surface on a roller body according to claim 14 , wherein the series of welding beads have a sinusoidal shape, a zigzag shape or a step-function shape comprising a left turn point and a right turn point region and wherein welding the second welding results in overlapping the first welding in the turn point region.
17. A method of forming a wear surface on a roller body according to claim 16 , wherein a speed of welding the second welding is lowered during welding in the turn point region thereby increasing a welding dwell time in the turn point region.
18. A method of forming a wear surface on a roller body according to claim 16 , wherein a welding current during welding of the second welding is increased during welding in the turn point region thereby increasing an energy input to the overlapping region in the turn point region.
19. A method of forming a wear surface on a roller body according to claim 16 , wherein a direction of a welding torch for welding the welding beads is changed from a radial direction between the left and right turning point regions to a tilted direction in the left and right turning point regions.