METHOD FOR THE MANUFACTURE OF MULTIMATERIAL ROLL AND THE MULTIMATERIAL ROLL

Abstract

In the present there is presented a method to manufacture multimaterial rolls, comprising method to produce base material containing part of the roll, joining of special material containing part for that, hot working at least part of the length of the roll ingot containing base material and special material, —so that at least requested roll ingot length and diameter are achieved as well as final treatment of the roll ingot—to manufacture finished roll. This method enables manufacture of large rolls, for example having length more than 3 meters as one integrated component without welding or mechanical joint—so, that in the working surfaces of the rolls is used steel with high amount of alloying elements and carbide forming alloying elements.

Claims

1. Method for the manufacture of multimaterial rolls comprising following steps: Base material containing part of the roll ingot is produced based on the selected method so, that the base material is such ferrous material which contains other alloying elements than iron maximum 15 weight-%, Special material containing part is joined to the base material containing parts of the roll ingot, which is produced using a suitable method so that special material density is at least 90% of its theoretical density and it forms 5-40 volume-% of the total volume of base material and special materials, The base material and special material containing part of the roll ingot is hot worked at least for the part of the length of the roll ingot so, that following is reached after hot working; The length of the roll is longer than roll ingot length before hot working, and/or The diameter of the roll is smaller than roll ingot diameter before hot working, and/or Roll shaft diameter is smaller than base material diameter before hot working, and Multimaterial special material layer thickness is at least 5 mm, wherein, before hot working at least the special materials containing parts of the roll ingot is encapsulated by capsule using at least 0.5 mm thick metal sheet and other metal components to protect encapsulated parts of the roll ingot during hot working.

2. Method according to claim 1, wherein special material is iron based material comprising Carbon content more than 0.8 weight-%, Carbide and nitride forming elements more than 12 weight-%, Volume fraction of carbides and nitrides 5-30 volume-%, Hardness heat treated for final operating condition more than HRC 35.

3. Method according to claim 1, wherein carbide average size in special material is smaller than 50 μm.

4. Method according to claim 1, wherein carbide average size in special material is 1-10 μm.

5. Method according to claim 1, wherein after encapsulation and before hot working of the roll ingot, The empty space below encapsulating capsule is evacuated or filled with the gas, and Hereafter the aforementioned empty space is closed gas tightly in order to prevent oxidation and/or decarburization.

6. Method according to claim 1, where the special material containing part is joined to the base material containing part of roll ingot, wherein between these materials is arranged interim layer containing interim layer material.

7. Method according to claim 1, wherein the special material containing part or the interim layer are joined to the base material containing part of the roll ingot by hot isostatic pressing, casting, molten metal spraying or spray forming, 3D printing, welding or other additive manufacturing method.

8. Method according to claim 1, wherein the special material is powder metallurgical materials.

9. Method according to claim 1, wherein the special material containing part of the roll ingot is joined to the base material containing part during manufacture of the special material.

10. Method according to claim 1, wherein the base material and special material are produced using additive manufacturing process like molten metal spraying, spray forming and 3D printing.

11. Method according to claim 1, wherein hot working is performed only for areas of the roll ingot that does not contain special material.

12. Method according to claim 1, wherein hot working is also performed for areas of the roll ingot that contain special material.

13. Method according to claim 1, wherein hot working is performed using hot forging, hot pressing or hot rolling at temperature of 800-1300° C.

14. Method according to claim 1, wherein Length of the finished roll is more than 3 meters, Special materials containing part forms coating on the outer surface of the finished roll so, that this forms coating for at least length of 500 mm of the total length of the finished roll, and Special material forms at least 10 mm thick coating for at least 80% of the total area of the coating.

15. Roll for hot or cold working, wherein it is produced according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIGS. 1a-1c illustrate principles of examples for optional manufacturing technologies for multimaterial starting ingots. FIG. 1a illustrates hot isostatic pressing, FIG. 1b illustrates molten metal spraying or spray forming, FIG. 1c illustrates casting.

[0044] FIGS. 2a-2c illustrate manufacture of multimaterial roll by hot working uncoated areas only so, that FIG. 2a illustrates multimaterial starting ingot before hot working, FIG. 2b illustrates hot working by forging, and FIG. 2c illustrates multimaterial roll after forging.

[0045] FIGS. 3a-3c illustrate manufacture of multimaterial roll so that multimaterial starting ingot is produced entirely using hot isostatic pressing as coated and encapsulated, and hot working is performed for the entire length of the ingot.

[0046] FIGS. 4a-4c illustrate manufacture of multimaterial roll so that in multimaterial starting ingot 3rd material is used between special material and base materials, and hot working is performed for the entire length of the ingot.

[0047] FIGS. 5a-5c illustrate manufacture of multimaterial roll so that in multimaterial starting ingot special material is coated into the roll working surface and special material is encapsulated with a sheet metal capsule, and hot working is performed hot forging for the entire length of the ingot.

[0048] FIGS. 6a-6c illustrate manufacture of multimaterial roll so that in the multimaterial starting ingot special material is coated into the working surface of the multimaterial roll and special material is encapsulated with sheet metal capsule, and hot working is performed for areas not containing special material.

[0049] FIGS. 7a-7d illustrate manufacture of multimaterial roll so that both materials of multimaterials starting ingot are produced and joined together simultaneously by casting having a steel plate separating them, ingot is encapsulated if necessary, and hot working is performed for the entire length of the ingot

[0050] FIGS. 8a-8d illustrate manufacture of multimaterial roll so that base material is shaped in order to make encapsulation and hot working easier, and hot working is performed for the entire length of the ingot.

[0051] FIGS. 9a-9c illustrate manufacture of multimaterial roll so that multimaterial starting ingot is coated using a selected method and ingot is encapsulated with a sheet metal capsule, and hot working is performed for the entire length of the ingot.

[0052] Figures are meant to describe inventive idea. Consequently, figures are not prepared in correct scale and they are not meant to determine particular parts or relative positioning of components.

DETAILED DESCRIPTION OF THE INVENTION

[0053] The text reference is made for drawings with following markings: [0054] 1 Roll [0055] 1′ Roll ingot [0056] 2 Working surface [0057] 3 Shaft [0058] 4 Base [0059] 5 Capsule [0060] 6 Interim layer [0061] 7 Separating steel plate [0062] 10 Forging tool [0063] 11 Forging die [0064] 12 Evacuation pipe [0065] 13 Weld end [0066] 14 Pressure vessel [0067] 15 Heating element [0068] A Special material [0069] B Base material [0070] C Interim layer material [0071] D Capsule material [0072] H.sub.V′ Diameter of the roll ingot [0073] H.sub.V Diameter of the roll [0074] H.sub.3 Diameter of the roll shaft [0075] L Length [0076] L.sub.A′ Length of the special area in the starting ingot [0077] L.sub.A Length of the special area of the roll [0078] L.sub.C Length of encapsulated areas [0079] L.sub.V′ Roll length before hot working [0080] L.sub.V Roll length

[0081] In the method of the invention there is manufactured multimaterial roll 1 so that it is possible to utilize advantageously selected working surface 2 special materials A of the roll together with roll base material B. The production method according to the invention allows manufacture of large, for example rolls having length L.sub.V more than 3 meters. The production method according to the invention enables manufacture of rolls 1 as one component without need for welding and mechanical joint so that in the working surfaces 2 of the rolls 1 there is high alloyed and a lot of alloy carbides containing steels. The production method according to the invention allows manufacture of rolls 1 with length L.sub.V more than even 7 meters so, that in their working surface 2 contain most high alloyed wear resistant steels.

[0082] Roll 1 length L.sub.V means total length of the roll 1. Usually this total length is axial length along the shafts 3 of the roll 1, like is illustrated in FIG. 2c. In this case length L.sub.V contains both the parts representing working surface 2 as well as shafts 3.

[0083] The working surface 2 of the roll 1 means that part of the roll 1, that is used for rolling and which during use of the roll 1 is in contact with the material rolled.

[0084] The multimaterial structure of roll 1 means that roll 1 contains several materials that are joined together using metallurgical or diffusion bonds without use of mechanical joints like shrink fitting, bolting or press joining

[0085] In the following multimaterial ingot is meant to be roll ingot 1′ after hot working produced at least from two materials, and when ingot 1′ is ready for finishing by for example machining and/or heat treatment.

[0086] Hot working is considered as forming of roll ingot 1′ dimensions at elevated temperatures so that [0087] Roll 1 length L.sub.V is as requested and larger than roll ingot 1′ length L.sub.V′ before hot working, and/or [0088] Roll 1 diameter H.sub.V is as requested and smaller than roll ingot 1′ diameter H.sub.V′ before hot working, and/or [0089] Diameter H.sub.3 of the roll 1 shaft 3 is as requested and smaller than respective parts diameter in the ingot 1′ before hot working

[0090] However, it should be understood that if several rolls 1 is manufactured from hot worked roll ingot 1′ for example by cutting roll ingot 1′ for several rolls 1, the length L.sub.V of each of these rolls 1 cut from hot worked ingot 1′ is not necessarily longer than roll ingot 1′ length L.sub.V′ before hot working. Hereafter, this special case is not repeated for the sake of clarity. However, even in this special case length L.sub.V of rolls 1 cut from hot worked ingot 1′ are as combined length longer than roll ingot 1′ length L.sub.V′ before hot working.

[0091] The hot working temperature can be for example over 1000° C., for example 1060-1200° C. or 1000-1175° C. or 1000-1200° C. or 1100-1250° C.

[0092] Hereafter, multimaterial starting ingot considered as multimaterial ingot according to previous description before heat treatment.

[0093] Based on the method according to the invention the roll 1 used in hot or cold rolling is produced as multimaterial structure using a suitable method so, that for the roll 1 working surfaces 2 a more wear resistant special material A is used and in roll base 4 and other parts a lower material cost but mechanical strong base material B is used.

[0094] The special material A part of the roll 1 may form maximum 60 volume-% or maximum 50 volume-% or maximum 40 volume-% or maximum 30 volume-% or maximum 20 volume-% or maximum 10 volume-% or maximum 5 volume-% or roll 1.

[0095] The special material A part of the roll may for example form a coating in the outer circumference of the finished roll. In this case coating length can be for example for 500 mm or 750 mm or 1000 mm or 1250 mm or 1500 mm length of the total length L.sub.V of the finished roll 1.

[0096] Special material A can be for example one of the steels AISI D2, AISI T15, AISI A11, AISI M3 and AISI M4. Characteristic for special material A is that in order to improve its wear resistance and hardness better than that of normal steels, its carbide content has been increased by higher carbon content and sufficient amount of carbide forming alloying elements

[0097] Carbon content of special materials A can be for example more than 0.8 weight-% or for example more than 1.1 weight-%.

[0098] Special material A may contain carbide and/or nitride forming alloying elements like chromium, molybdenum, vanadium, tungsten, niobium or titanium. Carbide and/or nitride forming alloying element content may be for example form than 8 weight-% or more than 12 weight-% or more than 15 weight-%.

[0099] Special material A may have when finished heat treated for example hardness more than HRC35 or more than HRC45.

[0100] The average carbide size of special material A can be for example smaller than 50 μm or smaller than 20 μm. Carbide size is determined by its largest dimension.

[0101] Base material B can be for example steel DIN 42CrMo4 or carbon steel EN S355. It is characteristic for base material B that its total alloying content is low and its carbon content is usually below 0.5 weight-%.

[0102] The part of multimaterial roll 1′ containing special material A like the working surface 2 in joined for base material B containing part like base 4 using a method suitable to produce and/or join the materials used. Joining may take place simultaneously with the manufacture of special material containing part A, like in weld cladding or when using hot isostatic pressing to produce powder metallurgical material or cladding to the surface of base material B containing part.

[0103] Based on the method of this invention it is also possible to produce roll ingot 1′ special material A containing part and base material B containing part simultaneously so, that they join to each other simultaneously with the manufacture at least other of the parts. FIG. 7a illustrates example, where both special material A containing part and base material B containing part are cast simultaneously and during cooling they bond to each other.

[0104] For the manufacture of multimaterial starting ingot 1′ for roll 1 one can use several methods, like for example is illustrated in FIG. 1a hot isostatic pressing, in FIG. 1b molten metal spraying or spray forming, or in FIG. 1c casting.

[0105] In the method illustrated in FIG. 1a special material A and base material B are located with joining surfaces facing each others, material is encapsulated around using sheet metal capsule and joining is performed at elevated temperature and pressure in a special high temperature pressure vessel. Special material A can be either as a powder particles or solid material. After this multimaterial starting ingot is ready for hot working.

[0106] In the method illustrated in FIG. 1b after coating using molten metal spraying or spray forming multimaterial starting ingot is ready for hot working.

[0107] In the method illustrated in FIG. 1c special material A and base material B are cast simultaneously into the mold using interim plate to separate melts from each other. After solidification multimaterial starting ingot is ready for hot working.

[0108] The special material A containing part manufacturing method is selected based on the composition of base material B, like steel. For example use of powder metallurgical or another rapid solidification technology to produce special material A is suitable for most high alloyed materials and their densification and joining for base material B is performed using hot isostatic pressing. On the other hand when using weld cladding the weldability of special material A and its availability as welding additive need to be considered. Additionally, due to the productivity limitations of weld cladding method it is mainly suitable for thin coatings. When using casting method to manufacture special material A containing part and join to base material B containing part, one has to consider castability of special material A and sufficient hot workability during hot working process stage of roll ingot 1′.

[0109] Also other production methods to manufacture multimaterial starting ingot 1′ for roll 1 can be utilized depending on the amount of alloying elements, microstructure and suitability for different stages of production.

[0110] The multimaterial starting ingot 1′ for roll 1 can be also produced so, that both special material A containing part and base material B containing part can be simultaneously manufactured and joined to each other. The advantage of this procedure is that amount of working stages is reduced and the base materials B containing part does not need to be machined and prepared for coating. Additionally, as both parts of the multimaterial starting ingot 1′ containing different materials cool together residual stresses of the ingot are lower.

[0111] FIGS. 7a-7d this type of production method with simultaneous manufacture and joining in case of casting method. In casting method special material A and base material B are poured into the mold simultaneously as illustrated in 7a. Special material A containing parts and base material B containing part are separated by metallic sheet 7 that can withstand casting temperature and can separate material A and B containing parts from each others. Hereafter, multimaterial starting ingot 1′ is hot worked according to FIG. 7d as it is according to FIG. 7b or encapsulated as illustrated in FIG. 7c. As a result of hot working is hot worked multimaterial ingot 1′ hot worked for requested thickness H.sub.V and length L.sub.V. This production is suitable also for other production methods than those based on casting, like powder metallurgically produced ingots where special material A and/or base material B are in powder form and compacted in one production stage for example by hot isostatic pressing to multimaterial starting ingot for hot working.

[0112] Another example of simultaneous production is variation method illustrated in FIG. 1b where first a base in manufactured using molten metal spraying or spray forming of base material B and subsequently spray forming is continued with special material A around base material B to produce multimaterials starting ingot. The advantage of this method as well as for method based on casting as illustrated in FIG. 7a is reduced risk for cracking because special material A cools down almost simultaneously with base material B. Additionally, manufacture and possible machining of base material B are avoided before manufacture of multimaterial starting ingot.

[0113] Based on the production method according this invention roll ingot 1′ is heated to elevated temperature entirely and partially after part containing special material A like working surface 2 in joined to base material B containing part like to base 4. Elevated temperature means for example 800-1300° C., or for example over 1000° C., like for example 1060-1200° C. or 1000-1175° C. or 1000-1200° C. or 1100-1250° C. For example, when hot working base material B in the ends of roll 1′ to increase length it is possible to heat only these areas for hot working temperature.

[0114] Using hot working roll ingot 1′ length can be increased at high temperatures to length L.sub.V′ long enough to produce final roll 1 so, that length L.sub.V of the final roll 1 is larger than roll ingot 1′ length L.sub.V′ before hot working. Additionally, with hot working it is possible to reach special material A structure and quality as well as to reach requested bond strength of special material containing part to base material containing part. Hot working can be performed for the entire length of ingot 1′, like illustrated in FIGS. 3-5 and 8-9, or only for part of it, like illustrated in FIGS. 2 and 6. If hot working is only performed for part of the roll ingot 1′, it can be performed for example only for that part of the ingot 1′ that does not contain special material A, like illustrated in FIGS. 2 and 6.

[0115] The extent of hot working can be decided based on the need of the area coated with special material A to guarantee quality and bond strength.

[0116] FIGS. 3a-3c present one example of hot working roll ingot 1′ so, that hot work item is hot isostatically pressed multimaterial starting ingot 1′ that contains outer layer capsule 5 made of capsule material D like illustrated in FIG. 3a. In this example hot working is performed according to FIG. 3b for the entire ingot 1′ in order to increase length of finished roll 1 for requested length L.sub.V.

[0117] FIGS. 4a-4c illustrates another example how hot working of roll ingot 1′ can be performed so that hot working is performed for multimaterial starting ingot 1′ that contains interim layer 6 of interim layer material C between special material A containing part and base material B containing part. In this example hot working is performed as illustrated in FIG. 4b for entire multimaterial starting ingot 1′.

[0118] The multimaterial ingot 1′ can be produced for example as illustrated in FIGS. 3a-3c and 4a-4c so, that special material A is bonded for the entire outer surface of base material B containing part so that the entire ingot length increases as multimaterial structures while in ingot cross section base material B containing part is surrounded by special material A containing part. As a result of hot working also in roll ingot 1′ extended for length L.sub.V′ special material A is possibly also in other areas of finished roll than in roll working surface 2. Consequently, in order to produce finished roll 1 it is possible to perform finish machining where special materials A can be removed for example from other surfaces than for the working surface or working surfaces 2 of finished roll 1. This production method is suitable for applications, where target is to coat main part of base material B containing part with special material A and/or hot working is requested to improve structure of special material A or its bond strength to base material B.

[0119] The roll multimaterial ingot 1′ can be also produced as illustrated in FIGS. 5a-5c and 6a-6c so that special material A has been bonded to base material B containing part of for parts of the outer surface. Using this approach one can save costs of higher quality and higher material cost special materials A and to use special materials A only in critical areas of the roll 1 like roll working surfaces. This allows use of hot working for the entire roll ingot 1′ as for example illustrated in FIGS. 5a-5c including special material A containing part, i.e. for example are of roll ingot 1′ surrounded by special material A. Optionally, multimaterial ingot of roll 1 can be hot worked only partially for example as illustrated in FIGS. 6a-6c from those areas, which does not contain special material A surrounding base material B containing part. This latter option is advantageous especially in situations where hot workability of special material A is poor and/or where special material A containing part does not require hot working for improving bond strength or material properties.

[0120] This type of situation, where bond strength between special material A and base material B is sufficient also without hot working, is for example when producing special material A containing part and then joining it to base material B containing part using hot isostatic pressing. In hot isostatic pressing as illustrated in FIG. 1a the special material A which is either in powder form or solid is encapsulated together with base material B containing part and hereafter capsule interior is evacuated. Subsequently, encapsulated ingot 1′ is transferred into high temperature pressure vessel 14 where ingot 1′ is subjected to combination of high temperature and isostatic pressure which results in bond formation between special materials A and base material B so there is created a joint between special material A containing part and base material B containing part. If special material A is in powder form, in compacts and densifies during production process. The temperature in the pressure vessel can be for example 1000-1200° C. The pressure used in the pressure vessel can be for example 80-150 MPa.

[0121] If hot working of the special material A containing part during hot working of the entire ingot is beneficial for example for improving properties of special material A and/or to increase bond strength between special material A containing part and base material B containing part, it is also possible to hot work special material A containing part like for example to hot work from roll ingot 1′ special material A containing part addition to other areas hot work from ingot 1′. FIGS. 5a-5c illustrate this method based on one example.

[0122] If roll ingot 1′ special material A containing part and base material B containing part are hot worked simultaneously, it is important to select hot working parameters like hot working temperature so, that hot working parameters are suitable for bot materials and so, that selected hot working parameters does not cause cracking for special material A and/or base material B. For example, combination of special material A AISI D2 and base material B DIN 42CrMo4 can be advantageously hot worked at the temperature of 1000-1200° C. After hot working in aforementioned case hot worked ingot can be transferred to furnace, which has temperature preferably at 650-750° C., for duration of 6 hours, and consequently furnace temperature can be slowly cooled down to room temperature.

[0123] Between some materials, like for example AISI T15 as special material A and carbon steel EN S355 used as base material B it can be beneficial to use interim layer material C between special material A and base material B to promote bond formation, to reduce residual stresses and/or to prevent formation of brittle microstructures. When using interim layer material C in roll ingot 1′ can interim layer material C as an interim layer 6 be between special material A containing part and base material B containing part. Use of interim layer material C as described above is illustrated in FIGS. 4a-4c according to one example. Interim layer material C can be for example quenched and tempered steel or nickel layer.

[0124] Before hot working, especially if also the material A containing parts of the roll 1's hot worked, it may be need to protect material A containing parts by encapsulating it with a capsule 5 as illustrated in FIGS. 8a-8d and 9a-9c. Capsule 5 can be sheet metal made of low carbon steel with good formability having carbon content below 0.1 weight-%. Capsule 5 can be used for example so that it covers the entire roll ingot 1′ as described in FIGS. 9a-9c. Capsule 5 thickness can be for example at least 0.5 mm or at least 1.5 mm.

[0125] Capsule 5 can protect special material A, which due to its high alloying element content is vulnerable for cracking. This type of protection i.e. encapsulation can prevent oxidation of cracks formed into special material A and especially for special material A containing part of roll ingot 1′. It is beneficial to prevent surface oxidation of cracks because oxidation reduces or even prevents closure of cracks during hot working as hot working progresses.

[0126] Also prevention of the oxidation of cracks and consequently prevention from repair of the interface between special material A containing part and base material containing part of roll ingot 1′ is easier as capsule 5 protects encapsulated surfaces and prevents their oxidation. Capsule 5 also protects special material A containing part from oxidation and decarburization reducing need for removal of decarburized layer during final machining of the roll ingot 1′. Additionally, encapsulation may reduce need for use of special furnaces like vacuum and protective atmosphere furnaces during heat treatment which are more expensive to use than normal furnaces. The volume in ingot 1′ below the capsule 5, even small one, on advantageous to evacuate i.e. remove air from empty volume or optionally fill with inert or non-detrimental gas like nitrogen, or gas mixture. Evacuation improves effects of encapsulation by preventing interfacial surface oxidation and by improving join quality below the capsule and the layer below it. After evacuation the empty volume can be sealed gas tight to prevent oxidation and/or decarburization.

[0127] If special material A containing part of roll ingot 1′ is joined to base material B containing part by hot isostatic pressing so, that a metal capsule 5 is used either around entire roll ingot 1′ or at least around special material containing part, this encapsulating capsule 5 does not need to be separately produced for hot working. However, when using another joining method like electroslag re-melting, casting, spraying, spray forming or weld cladding, the encapsulating capsule 5 need to be produced separately.

[0128] Especially in situations where in the multimaterial starting ingot 1′ the entire base materials B containing part is not coated with special material A, it is possible to encapsulated special material A containing part by welding capsule 5 to base material B surrounding special material. This is illustrated for example in situations described in FIGS. 5a-5c, 6a-6c and 8a-8d.

[0129] In FIGS. 8a-8d is illustrated example to create a shaped base material B part roll ingot 1′ before joining special material A containing part so, that encapsulation after work working is easier. As illustrated in FIG. 8a cavity is produced for base material B containing parts by machining, casting or forging to the area where special material A is joined i.e. where the special material A containing part is forms. FIG. 8c illustrates production of special material A containing part surrounded by capsule 5. FIG. 8d illustrates how hot working is performed for the multimaterial starting ingot 1′ described previously. In this case illustrated in FIGS. 8a-8d encapsulating capsule 5 can be produced from rolled sheet metal or by using tubular capsules 5.

[0130] The production method according to this invention allow manufacture of multimaterial roll 1 by cold or hot working. According to production process on invention a multimaterial roll 1 can be produced as one integrated component without welding and/or mechanical joint. Especially, production method according to invention is suitable to manufacture large multimaterial rolls 1 for lengths L.sub.V more than 3 meters or more than 3.5 meters or more than 4 meters.

[0131] The invention is characterized in that the method comprises following steps: [0132] A base material B containing part for roll ingot 1′ is produced by forging, welding or casting, [0133] Necessary machining, surface cleaning and installation of optional interim layer material C containing capsule 6 are performed for base material B containing parts of the roll ingot 1′ [0134] Base material B containing part of roll ingot 1′ and possible integrated interim layer 6 are preheated if preheating is required due to requirements of special material A joining methods and/or due to requirements of entire production process of roll 1 for example in cast bonding, additive manufacturing like molten metal spraying, spray forming or weld cladding [0135] A special material A containing part of roll ingot 1′ is formed for example by coating base material containing part or part of its surface by special material A which from better wear resistance and other properties point of view is better suited for multimaterial roll, [0136] Hot working is performed for the roll ingot 1′ in order to reach requested length and/or to optimize special material A containing part or to improve bond strength between special material containing part A and base material containing part B, [0137] Finishing processing is performed for hot worked roll ingot 1′, like for example heat treatment and/or machining, to create finished roll.

[0138] It is essential to observe that both materials in multimaterial starting ingot are before hot working dense or almost dense and from performance point of view good enough for several less demanding applications that roll applications.

[0139] Additionally, in the method according to this invention surface of roll ingot 1′ or part of it can be encapsulated by capsule 5 before heat treatment. Encapsulation is always performed when using hot isostatic pressing and when special material A is powder form. Encapsulation can be, however, performed as previously described also to guarantee successful hot working and to minimize decarburization when using other production and joining methods for special material A.

[0140] Furthermore, in the production method according to this invention can be used interim layer 6 of interim layer material C between special material A part and base material B part of the roll ingot 1′ to reduce detrimental interfacial reactions. Interim layer 6 can be installed for example to surface of base material B containing part by weld cladding, spraying or thin sheet or band.

Example 1

[0141] Base material part of roll ingot 1′ is produced so that base material B is 0.15 weight-% carbon containing structural steel.

[0142] Around ingot 1′ is coated by hot isostatic pressing at temperature of 1100° C. and pressure of 100 MPa special material A, which is tool steel having carbon content of 1.6 weight-% total amount of carbide forming alloying elements (vanadium, molybdenum, chromium) is 15 weight-%:a (vanadium 9.5 weight-%:a, chromium 5.0 weight-%:a ja molybdenum 0.5 weight-%:a). This way is produced special material A containing part around base material B containing part of roll ingot 1′. For hot isostatic pressing production stage a encapsulating capsule 5 is made around base material B containing part and special material A containing part using low carbon structural steel (carbon content 0.1 weight-%), which is evacuated before hot isostatic pressing.

[0143] The multimaterial ingot 1′ is hot worked by forging after hot isostatic pressing at temperature of 1060-1200° C. for the entire length of the ingot 1′ so, than the encapsulating metallic capsule 5 is maintained in the ingot during hot working. Encapsulating capsule 5 is removed after hot working by machining.

[0144] In this example multimaterial ingot 1′ length L.sub.V′ of the roll ingot before hot working is 2 meters and diameter H.sub.V′ is 0.5 meters, and after hot working length L.sub.V′ is 5.5 meters and diameters H.sub.V′ is 0.15 meters.

Example 2

[0145] The base material B part of roll ingot 1′ is produced as forging so that base material B is AISI H13 steel.

[0146] Around this ingot 1′ is joined by hot isostatic pressing at temperature of 1150° C. and pressure of 120 MPa special material A, which is powder metallurgical tool steel AISI M4. Special material A is joined only to that part of the roll ingot 1′ containing base material B, which forms working surface 2 of the roll 1 after subsequently performed hot working of ingot 1′. This way is produced special material A containing part to join base material B for ingot 1′.

[0147] The multimaterial ingot 1′ produced this way is hot worked after hot isostatic pressing at temperature of 1000-1175° C. so, that both ends of the ingot 1′ not coated with special material A are forged longer and special material A is not hot worked. Hot working is not performed for the part of ingot 1′ containing special material A, on the contrary it is performed for other parts of roll ingot 1′.

[0148] In this example the length L.sub.V′ of multimaterial ingot 1′ before hot working is 2 meters and diameter H.sub.V′ 0.5 meters, and after hot working length L.sub.V′ is 5.5 meters and diameter H.sub.V′ is 0.15 meters.

Example 3

[0149] Base material B containing part of roll ingot 1′ is produced as steel forging so that base material B is quenched and tempered steel.

[0150] Around this 1′ is joined for entire length L.sub.V′ of ingot 1′ pituudelle L.sub.V′ by casting bonding special material A which is tool steel AISI D2. This way is produced special material A containing part of ingot 1′ around base material B containing part.

[0151] The multimaterial ingot 1′ of the roll is encapsulated by capsule 5, which is 10 mm thick structural steel containing 0.1 weight-% carbon. The encapsulated area is evacuated by removing the air away.

[0152] Subsequently, the ingot 1′ is hot worked by forging at temperature of 1050-1200° C. for the entire length including area coated with special material A.

[0153] After hot working ingot 1′ is cooled down slowly in the furnace to room temperature, and hereafter it is finish machined to requested roll 1 length of L.sub.V and heat treated by quenching and tempering to hardness of HRC52.

[0154] In this example multimaterial ingot 1′ length L.sub.V′ before hot working is 2 meters and diameter H.sub.V′ is 0.5 meters, and after hot working length L.sub.V′ is 8 meters and diameter H.sub.V′ is 0.125 meters.

Example 4

[0155] For the part of roll ingot 1′ base material containing part, which after hot working performed afterwards represent working surface 2 of roll 1, is formed interim layer 6 using interim layer material C as 1 mm thick nickel layer.

[0156] After this coating for the areas coated of ingot 1′ a special material A is joined to its outer circumference at temperature of 1120° C. and pressure of 105 MPa, which is tool steel AISI T15. In this process is created special material A containing part on the interim layer 6.

[0157] After hot isostatic pressing multimaterial ingot 1′ is hot worked by forging at 1000-1200° C. for the entire length including area coated with special material A.

[0158] In this example multimaterial ingot 1′ length L.sub.V′ before hot working is 1.5 meters and diameter H.sub.V′ is 0.5 meters, and after hot working length L.sub.V′ is 6 meters and diameters H.sub.V′ is 0.125 meters.

Example 5

[0159] Base material B containing part of roll ingot 1′ is produced as a steel forging so that base material B is carbon steel.

[0160] Special material A containing part is produced separately using hot isostatic pressing so, that special material A is tool steel AISI D2. This special material A containing part is machined as a separate part for a such geometry, that is can be installed around base material B containing part of roll ingot 1′.

[0161] This multimaterial ingot 1′ is encapsulated with a capsule 5 so, that capsule is 10 mm thick structural steel with 0.1 weight-% carbon. Hereafter, encapsulated capsule is evacuated by removing air.

[0162] Subsequently, hot isostatic pressing is performed for multimaterial ingot 1′ at temperature of 1140° C. and pressure of 100 MPa in order to join separately produced special material A containing part around base material B containing part.

[0163] After this areas which are not coated with special material multimaterial ingot 1′ of the roll 1 are hot worked at 1000-1175° C. in order to reach total roll 1 length of L.sub.V. So, hot working is performed for other areas of roll ingot 1′ than those containing special material A.

[0164] In this example the multimaterial ingot 1′ length L.sub.V′ before hot working is 1.5 meters and diameter H.sub.V′ is 0.5 meters, and after hot working length L.sub.V′ is 6 meters and diameters H.sub.V′ is 0.125 meters.

Example 6

[0165] Base material B containing part of roll ingot 1′ is produced as a steel forging so, that base material B is quenched and tempered steel.

[0166] The special material part A is produced around base material containing part of roll ingot 1′ so, that into the surface of base material B containing part is weld cladded by submerged arc welding a special material A which is tool steel having carbon content of 1.5 weight-% and chromium content of 15 weight-%.

[0167] After welding the weld cladded area in encapsulated with a capsule 5 and encapsulated area is evacuated removing area from the capsule.

[0168] Hereafter, ingot 1′ is hot worked by forging at temperature of 1100-1250° C. so, that hot working is performed for the weld cladded areas.

[0169] After hot working multimaterial ingot 1′ is finish machined and heat treated by quenching and tempering to hardness of HRC50.

[0170] In this example multimaterial ingot length L.sub.V′ before hot working is 2 meters and diameter H.sub.V′ is 0.3 meters, and after hot working the length L.sub.V′ is 4.5 meters and diameter H.sub.V′ is 0.2 meters.

Example 7

[0171] Roll ingot 1′ is cast in vertical position so, that [0172] Special material A containing part and base material B containing part of roll ingot 1′ are produced simultaneously so, that special material A and base material B are cast simultaneously, [0173] In the casting mold is separating plate 7 between special material A and base material B, which is 10 mm thick steel sleeve, [0174] Special material A is tool steel AISI D2, and [0175] Base material B is carbon steel.

[0176] After casting multimaterial ingot 1′ is encapsulated entirely with a capsule 5 so, that capsule 5 is 15 mm thick and its material is 0.1 weight-% carbon containing structural steel.

[0177] This encapsulated roll ingot 1′ is hot worked by forging at temperature of 1000-1200° C.

[0178] In this example multimaterial ingot 1′ length L.sub.V′ before hot working is 1.5 meters and diameter H.sub.V′ is 0.4 meters, and after hot working length L.sub.V′ is 3 meters and diameter H.sub.V′ is 0.28 meters.

Example 8

[0179] First, base material B is produced by spray forming and hereafter immediately before cooling of base material special material A is spray formed for part of the base material B so, that [0180] Base material B and special material A containing parts of the roll ingot 1′ are produced sequentially so that base material temperature is not cooling below 300° C. before start of spray forming of special material A, [0181] Special material A is tool steel AISI M3, and [0182] Base material B is steel AISI H13.

[0183] After the two phase spray forming multimaterial ingot 1′ is encapsulated entirely with a capsule so, that capsule 5 is 10 mm thick and made of structural steel containing 0.1 weight-% of carbon.

[0184] The encapsulated roll ingot 1′ is hot worked by forging at temperature of 1000-1200° C.

[0185] In this example multimaterial ingot 1′ length L.sub.V′ before hot working is 1.5 meters and diameter is H.sub.V′ on 0.4 meters, and after hot working length L.sub.V′ is 3 meters and diameter H.sub.V′ is 0.28 meters.

(End of Examples)

[0186] The inventive idea also included multimaterial hot or cold working roll 1, which includes part produced of base material B, part produced of more wear resistant coating material A and possibly encapsulating capsule 5 and/or interim layer with interim layer material C between special material A and base material B.

[0187] The method according to this invention enables manufacture of rolls containing special material A with hardness at least HRC 35 after heat treatment and carbide volume fraction at least 5 volume-%.

[0188] The examples presented are intended to describe the inventive nature. Consequently, they should not be considered as concrete description of manufacturing process according to inventive idea.