Method for Producing a Component Having a Core Portion Which Consists of Steel

Abstract

The invention sets out a method for simply producing components which are suitable for use under high loads and risks of wear and which have a core portion which consists of a metal material and a wear-resistant layer on a peripheral surface of the core portion. To this end, there is provided according to the invention a) a core portion blank which consists of the metal material and whose dimension in a first spatial direction is greater than the desired finished dimension of the core portion of the component in the relevant spatial direction and whose dimension in a second spatial direction is smaller than the desired finished dimension of the core portion of the component in this second spatial direction; b) there is applied a material which forms the wear-resistant layer to the peripheral surface in such a manner that the material and the core portion blank form a stable composite body; and c) the composite body is shaped to form the component by the composite body being extended in the direction of the second spatial direction and being compressed in the direction of the first spatial direction until the dimensions thereof in the spatial directions at least correspond to the desired finished dimensions of the component in these spatial directions and the wear-resistant material is present on a peripheral surface of the component. Optionally, finishing processing of the component may follow.

Claims

1. A method for producing a component which has a core portion which comprises a metal material, in particular a steel, and a wear-resistant layer which is carried by the core portion and which is present on a peripheral surface of the core portion, comprising the following operating steps: a) providing a core portion blank which consists of the metal material and whose dimension in a first spatial direction is greater than the desired finished dimension of the core portion of the component in the relevant spatial direction and whose dimension in a second spatial direction his smaller than the desired finished dimension of the core portion of the component in this second spatial direction; b) applying a material which forms the wear-resistant layer in the finished component to the peripheral surface of the core portion blank in such a manner that the applied material and the core portion blank form a stable composite body; c) shaping the composite body to form the component, wherein the composite body during the shaping is extended in the direction of the second spatial direction and is compressed in the direction of the first spatial direction until the dimensions of the composite body in the spatial directions at least correspond to the desired finished dimensions of the component in these spatial directions, wherein the material which forms the wear-resistant layer is present on a peripheral surface of the component; d) optional finishing processing of the component.

2. The method according to claim 1, wherein the component has a rotationally symmetrical shape.

3. The method according to claim 1, wherein the core portion blank has a cylindrical shape.

4. The method according to claim 1, wherein in the operating step b), the wear-resistant material is applied in powder form to the peripheral surface of the core portion blank and is connected by means of hot isostatic pressing to the core portion blank to form the composite body.

5. The method according to claim 1, wherein in the operating step b), the wear-resistant material is applied by means of deposition welding to the peripheral surface of the core portion blank and is connected thereto to form the composite body.

6. The method according to claim 1, wherein the shaping of the composite body to form the component is carried out by means of forging.

7. The method according to claim 1, wherein the component is a roller for hot or cold rolling metal strips, and in that on each of the end faces of the core portion thereof a journal which is orientated coaxially relative to the core portion is formed.

8. The method according to claim 7, wherein when the material which forms the wear-resistant layer is applied (operating step b)) starting from the respective end face of the core portion blank there is recessed over a length which is measured axially parallel with the longitudinal axis of the journal which is intended to be formed and which is sized in such a manner that the volume of the core portion blank over which the recessed length of the peripheral surface extends corresponds to at least the volume of the journal which is intended to be formed on the respective end face of the finished roller.

9. The method according to claim 7, wherein the journals are formed using forging technology (operating step d)).

10. The method according to claim 1, wherein the component is a shaft, roller, or a barrel extruder.

11. The method according to claim 1, wherein the steel of the core portion blank is a construction steel.

12. The method according to claim 1, wherein the shaping of the composite body in the operating step c) is carried out in such a manner that the component after the operating step c) in at least one spatial direction has an overdimension with respect to the desired finished dimension of the component in this spatial direction and in that the component in the operating step d) is subjected to a finishing processing operation by means of a machining processing operation such that the dimension thereof in the relevant spatial direction corresponds to the desired finished dimension.

Description

[0041] The invention is explained in greater detail below by reference to drawings which show embodiments. In the schematic Figures:

[0042] FIG. 1 is a lateral sectional view of a core portion blank which is prepared in a capsule for a hot isostatic pressing;

[0043] FIG. 2 is a sectional view corresponding to FIG. 1 of the core portion blank after the application of a powder material which forms a wear-resistant layer;

[0044] FIG. 3 is a view corresponding to FIGS. 1 and 2 of a composite body which is formed from the core portion blank and the wear-resistant material;

[0045] FIG. 4 is a lateral sectional view of a shaft which is formed from the composite body;

[0046] FIG. 5 is a lateral sectional view of a core portion blank during the application of a wear-resistant material by deposition welding;

[0047] FIG. 6 is a view corresponding to FIG. 5 of the composite body which is obtained after the conclusion of the application of the wear-resistant material to the core portion blank according to FIG. 5;

[0048] FIG. 7 is a lateral view corresponding to FIGS. 5 and 6 of a roller for rolling flat steel products.

[0049] An objective of a first test was to produce a shaft 1 of the type illustrated in FIG. 4. This shaft 1 has four shaft portions 2, 3, 4, 5, the diameter D2, D3, D4, D5 of which decreases from the one outer shoulder 2 as far as the other outer shoulder 5 of the shaft 1 in a stepped manner. At the same time, the shaft portions 2-5 have different part-lengths L2, L3, L4, L5 which are measured in the direction of the rotation axis A of the shaft 1.

[0050] The shaft 1 having the total length L1 comprises a core portion 6 which is produced from the construction steel C20 which is standardised under the material number 1.0402 and the composition of which is set out in Table 1. There is formed on the peripheral surface of the portions 2-5 of the core portion 6 a layer 7 which consists of a first variant FeCrV10 of the wear-resistant cold work steel FeCrV10 which is known per se. The composition of the material FeCrV10 of the layer 7 is also set out in Table 1.

[0051] For the production of the shaft 1, there was provided a cylindrical core portion blank 8 which consists of the steel C20 and whose length L8 which is measured in the spatial direction X which is orientated axially parallel with the rotation axis A corresponds to a fraction of the length L1 and had such dimensions that the base body could be readily placed with a capsule 9 which surrounds it in a conventional device (not shown here) for hot isostatic pressing (HIPen). At the same time, the diameter D8 of the core portion blank 8, which is measured in the spatial direction Y orientated perpendicularly to the spatial direction X, has such dimensions that the material volume of the core portion blank 8 corresponded to the entire material volume of the core portion 6 of the shaft 1 which is distributed over the shaft portions 2-5.

[0052] The tubular capsule 9 which surrounds the core portion blank 8 for the HIPen consisted of a steel sheet which is conventionally used for these purposes. In this case, its diameter had such dimensions that, with a coaxial orientation of core portion blank 8 and capsule 9, between the peripheral surface 10 of the core portion blank 8 and the inner surface of the capsule 9, a circumferential free space 11 was present. The end sides of the capsule 9 have been tightly closed after the positioning of the core portion blank 8 by sheet metal covers which closely abutted the end sides of the core portion blank 8.

[0053] Subsequently, an alloy powder M which consists of the material FeCrV10 and which has a grain suitable for these purposes was poured into the space 11 via a supply which is not shown here and which is provided on the capsule 9 in conventional manner so that the peripheral surface 10 of the core portion blank 8 was completely covered by alloy powder M.

[0054] Subsequently, the capsule 9 was placed in the device (not shown) for HIPen, in which the alloy powder M was densified in conventional manner at a pressure of approximately 100 MPa and temperatures of from 900 to 1200 C. and sintered to form a dense layer 12. As a result of the solid body diffusion processes which took place in this instance, a stable, materially bonded connection of the layer 12 was produced with respect to the core portion blank 8 at the same time.

[0055] After completion of the hot isostatic pressing operation, the capsule 9 was separated from the composite body 13 which was formed from the core portion blank 8 and the layer 12 which was applied thereto by the HIPen and which consists of the wear-resistant cold work steel FeCrV10.

[0056] The composite body 13 was then shaped by forging in a manner also known per se in a plurality of steps to form the shaft 1.

[0057] It was found that it was readily possible to shape a component, such as the shaft 1, from the composite body 13, the length L1 of which is considerably greater than the length L8 of the composite body 13 and the core portion blank 8 which forms the starting product for producing the shaft 1 and the diameter D2, D3, D4, D5 of which is substantially smaller than the diameter D8 of the core portion blank 8. In this case, it was also found to be readily possible to construct on the shaft 1 a journal-like shaft portion 5, the diameter D5 of which was substantially smaller than the diameter D2 of the thickest shaft portion 2 of the shaft 1.

[0058] Where necessary, the shaft 1 can be finally processed mechanically after the forging in a conclusive manner and can be subjected to a thermal processing operation in order to adjust the mechanical properties thereof.

[0059] In the finished shaft 1, the material of the core portion blank 8 of the composite body 13 forms the core portion 6 and the material M of the layer 12 of the composite body 13 forms the wear-resistant layer 7.

[0060] The above-described method of producing can accordingly be transferred readily to the production of other elongate components, such as a barrel extruder for processing plastics materials or a roller for rolling metal strips or sheets, in which comparable geometric relationships exist between the individual component portions.

[0061] In a second test, the roller 21 illustrated in FIG. 7 was intended to be produced and was provided as an operating roller in a roll rack for rolling steel strip. The roller 21 having a total length L21 of up to 10 m was intended to have a core portion 22 which also consists of the already above-mentioned steel C20 and a bale portion 23, at the peripheral surface of which a wear-resistant layer 24 is present. At the same time, a respective journal 26, 27 was intended to be formed on the end sides 25, 25 of the roller 21 and the roller 21 was intended to be supported therein during use.

[0062] For producing the roller 21, there was provided a cylindrical core portion blank 28 which consisted of the steel C20 and the length L28 of which similarly to the length L8 in the core portion blank 8 corresponded only to a small fraction of the length L21 of the roller 21 which was intended to be produced. At the same time, the diameter D28 of the core portion blank 28 was so much greater than the diameter D22 of the core portion 22 of the roller 21 that the material volume of the core portion blank 28 was greater by a given overdimension than the material volume taken up by the core portion 22 and the journals 26, 27. The overdimension of the material volume of the core portion blank 28 had such dimensions in this case that after the subsequently explained operating steps in the region of the journals 26, 27 which are formed from the material of the core portion blank 28, there was still available enough material volume for a machining finishing processing operation.

[0063] A layer 30 which is formed from a wear-resistant material was applied to the peripheral surface 29 of the core portion blank 28 by Plasma Powder Deposition Welding, also referred to in technical language as Plasma Transferred Arc Welding, abbreviated to PTA welding.

[0064] In a first variant of the second test, the layer 30 was formed from a powder P which is present with a grain of from 63 to 160 m and which consisted of the second variant FeCrV10 of the cold work steel FeCrV10 as set out in Table 2.

[0065] In a second test variant, a powder which consisted of the high-speed steel HSS30 and which has a grain of from 63 to 180 m was used as the powder P. The composition of the material HSS30 which is standardised under the material number 1.3294 is also set out in Table 2.

[0066] Both the material FeCrV10 and the material HSS30 are typical representatives of materials which are conventionally used for highly wear-resistant layers which are produced by powder metallurgy of components, such as rollers and barrel extruders and which are subjected during practical use to high pressure loads or the risk of abrasive wear. The second test described here showed that both materials FeCrV10 and HSS30 used for the wear-resistant layer 24 are suitable for the purposes according to the invention to the same extent.

[0067] For the deposition welding, the core portion blank 28 is clamped on a rotating bench which is not shown here and caused to rotate. A welding torch S is in this case moved axially parallel with the rotation axis A and thus produces a plurality of layers of weld beads 31 which extend radially round the core portion blank 28 on the peripheral surface 29.

[0068] The positioning of the weld beads 31 is in this case possible in a discontinuous method, in which the advance of the welding torch S is carried out respectively after a revolution of the core portion blank 28 and adjacent annular weld beads 31 are produced, or in a continuous method, in which a continuous weld bead 31 which extends helically round the core portion blank 28 is produced respectively by the core portion blank 28 moving at the same time synchronously with respect to the continuous advance of the welding torch S.

[0069] Alternatively, however, it is also possible to produce axially extending weld beads 31 on the peripheral surface 29 respectively by the core portion blank 28 being stopped until the welding torch S has covered the length L28 of the core portion blank 28.

[0070] It should generally be noted that by repeating the deposition welding process the layer thicknesses which are required for the subsequent shaping process can be produced by the resultant multiple-layer structure. Furthermore, it is thereby also possible to produce a graduated layer structure in which different materials are welded one after the other. Thus, the properties of the steel core as far as the edge of the outer layer can be constructed with a gradient. Where necessary, scale residues or other welding residues which are present on the outer surface of the applied weld beads 31 can be removed between the individual operating steps. If a rotating bench is used to drive the core portion blank 28, it can be carried out in the same clamping composition as the deposition welding itself.

[0071] When the weld beads 31 are applied, an end portion of the peripheral surface 29 is recessed adjacent to the end sides 32, 33 of the core portion blank 28, respectively, so that at that location no wear-resistant material P is deposited.

[0072] After the deposition welding, the composite body 34 which is formed from the core portion blank 28 and the layer 30 which is applied thereto by the deposition welding was hot-shaped in a plurality of steps by forging in a manner known per se to form the roller 21. In this case, the core portion 22 of the roller 21 was formed from the core portion blank 28 of the composite body and the wear-resistant layer 24 of the roller 21 was formed from the layer 30 of the composite body.

[0073] The material volume of the core portion blank 28 not occupied with wear-resistant material P was used in the shaping for producing the journals 26, 27. Alternatively, it is naturally also possible to occupy the peripheral surface 29 of the core portion blank 28 completely with the layer 30 and to subsequently remove in a machining manner the wear-resistant layer 24 which is present in the region of the journals after the shaping of the composite body 34.

[0074] The roller 21 obtained was subjected to a thermal processing operation and subsequently processed in a machining manner in order to ensure the mechanical properties thereof and the required dimensional stability.

[0075] It should generally be noted that during the technical shaping by forging and the thermal processing the occurrences of grain coarsening and undefined thermal processing states present in the region of the thermal influence zone of the deposition welding in the core portion 22 have been eliminated. As a result of the production steps forging and thermal processing, a grain refining took place in the entire composite body 34 and a defined thermal processing state was produced. In this case, the production method which is simplified with respect to the HIP process was found to be a significant advantage of the second production method which is based on deposition welding.

REFERENCE NUMERALS

[0076] 1 Shaft [0077] 2-5 Shaft portions of the shaft 1 [0078] 6 Core portion of the shaft 1 [0079] 7 Layer comprising a wear-resistant material M [0080] 8 Core portion blank [0081] 9 Capsule [0082] 10 Peripheral surface of the core portion blank 8 [0083] 11 Space in the capsule 9 [0084] 12 Layer applied to the peripheral surface 10 [0085] 13 Composite body [0086] 21 Roller [0087] 22 Core portion of the roller 21 [0088] 23 Bale portion of the roller 21 [0089] 24 Wear-resistant layer of the roller 21 [0090] 25, 25 End sides of the roller 21 [0091] 26, 27 Journals of the roller [0092] 28 Core portion blank [0093] 29 Peripheral surface of the core portion blank 28 [0094] 30 Layer formed from a wear-resistant material on the peripheral surface 28 [0095] 31 Weld beads [0096] 32, 33 End sides of the core portion blank 28 [0097] 34 Composite body [0098] A Rotation axis of the components 1, 21 [0099] D1 Diameter of the core portion of the shaft portion [0100] D2-D5 Diameter of the shaft portions 2-5 [0101] D8 Diameter of the core portion blank 8 [0102] D28 Diameter of the core portion blank 28 [0103] D22 Diameter of the core portion 22 of the roller 21 [0104] L1 Total length of the shaft 1 [0105] L2-L5 Part-lengths L2, L3, L4, L5 of the shaft 1 [0106] L8 Length of the core portion blank 8 [0107] L21 Total length of the roller 21 [0108] L28 Length of the core portion blank [0109] M Alloy powder [0110] P Powder [0111] S Welding torch [0112] X, Y Spatial directions

TABLE-US-00001 TABLE 1 Indications in % by weight, balance iron and inevitable impurities C Si Mn P S Cr Mo Ni V C20 0.20 <0.40 0.55 <0.045 <0.045 <0.40 <0.10 <0.40 FeCrV10 2.55 1.19 0.66 0.022 0.041 5.08 1.36 0.08 9.63

TABLE-US-00002 TABLE 2 Indications in % by weight, balance iron and inevitable impurities C Si Mn P S Cr Mo Co W V FeCrV10 2.31 0.85 0.78 0.016 0.013 4.25 1.36 9.9 HSS30 1.32 0.46 0.27 0.017 0.015 4.07 5.10 8.29 6.53 3.10