Claims:I/We claim:
1. A laser clad comprising the following composition by weight:
0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
2. The laser clad as claimed in claim 1, wherein the laser clad is supermartensitic.
3. The laser clad as claimed in claim 1, wherein Carbon (C) is 0.01-0.03%.
4. The laser clad as claimed in claim 1, wherein Molybdenum (Mo) is 2.7%.
5. The laser clad as claimed in claim 1, wherein Nickel (Ni) is 4.2%.
6. The laser clad as claimed in claim 1, wherein Cobalt (Co) is 4.6%.
7. The laser clad as claimed in claim 1, wherein Manganese (Mn) is 0.3 %.
8. The laser clad as claimed in claim 1, wherein Chromium (Cr) is 12.35%.
9. The laser clad as claimed in claim 1, wherein Silicon (Si) is 0.6%.
10. The laser clad as claimed in claim 1, wherein remaining balance is Iron(Fe).
11. A caster roll comprising:
a roll substrate with a laser clad, the laser clad comprising, by weight, 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
12. The caster roll as claimed in claim 14, wherein the roll substrate is a top zone roll strand.
13. The caster roll as claimed in claim 14, wherein the roll substrate comprises 0.18-0.23% Carbon (C), 0.56% Manganese (Mn), 12.7% Chromium (Cr), 0.25% Nickel (Ni), 0.045% Molybdenum (Mo), 0.009% Sulphur (S), 0.03% Phosphorus (P), 0.5% Silicon (Si), 0.08% Copper (Cu), 0.034% Vanadium (V), and the rest being Iron (Fe) and inevitable impurities.
14. The caster roll as claimed in claim 14, wherein the roll substrate diameter ranges from 130 mm to 150 mm.
15. A method for laser cladding on a caster roll, the method comprising:
cleaning a roll substrate by machining the surface of the roll substrate;
rotating the roll substrate around its axis of symmetry;
forming a melt pool on the roll substrate using a laser beam; and
feeding a laser clad in powder form into the melt pool using a coaxial nozzle to perform the laser cladding on the roll substrate,
wherein the laser clad comprising, by weight, 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
16. The method as claimed in claim 18, wherein the roll substrate comprises 0.18-0.23% Carbon (C), 0.56% Manganese (Mn), 12.7% Chromium (Cr), 0.25% Nickel (Ni), 0.045% Molybdenum (Mo), 0.009% Sulphur (S), 0.03% Phosphorus (P), 0.5% Silicon (Si), 0.08% Copper (Cu), 0.034% Vanadium (V), and the rest being Iron (Fe) and inevitable impurities.
, Description:CASTER ROLL MANUFACTURED WITH LASER CLADDING

TECHNICAL FIELD
[0001] The present disclosure, in general, relates to the continuous casting of steel slabs, preferably thin slab casting and rolling.
[0002] In particular, the present disclosure relates to a laser clad and a caster roll having a roll substrate with said laser clad.

BACKGROUND
[0003] Background description includes information that may be useful in understanding the present subject matter. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed subject matter, or that any publication specifically or implicitly referenced is prior art.
[0004] Continuous casting setups for thin slab casting are enormous and involve complex production units. A height of these setups is approximately 14 meters. Along with this height, a strand is generally consisting of around 5 segments. Each segment has around 50 rolls with varying diameters ranging from 130-170 mm depending on the position of the roll with respect to the strand.
[0005] A schematic of a conventional casting setup 100 is shown in FIG 1. As shown in FIG. 1, the casting setup 100 includes a ladle 102, a tundish 104 connected to an output opening of the ladle 102, a copper mould 106 receiving molten steel from an entry nozzle 108 connecting the tundish 104 and the copper mould 106; and a set of rolls 110 positioned in front of an outlet of the copper mould 106. In an aspect, the set of rolls are broadly categorized as top zone rolls 110-T and lower zone rolls 110-L.
[0006] The set of rolls 110 are generally subjected to high wear and tear as they have to move the moulded molten steel out of the copper mould 106. In particular, due to a substantial solidification of the steel strip, the lower zone rolls 110-L have to face more wear and tear in comparison to the top zone rolls 110-T. Accordingly, in order to improve productivity, reduce downtime loss, and eliminate surface grinding costs, manufacturers of rolls 110 are forced to explore materials with superior performance under extreme harsh environments.
[0007] Further, the temperature of out coming molten steel and the surface of the first solidified slab (just below the copper mould 106) received by the rolls 110 is around 1500 °C. As the slab solidifies along the strand, the temperature of the slab decreases to about 800-900 °C. In an aspect, external water spray cooling is performed to cool the slab (and the rolls 110). The water is sprayed between the rolls 110 to maximize slab cooling. The combination of very high temperatures, and humid and corrosive (due to an influx of mould powder) environment results in very harsh conditions for the rolls 110. The rolls 110 are hollow rolls and are made with martensitic stainless steel quenched and tempered at 800 °C to provide a compromise between wear resistance and corrosion resistance. However, mechanical wear of these rolls 110 is still a concern leading to frequent removal of rolls 110 for surface grinding and to the rejection of the rolls 110 after surface removal to a certain limit.
[0008] Various approaches have been suggested in the state of the art to improve thermal fatigue resistance and surface quality of the rolls 110. One of the approaches is laser cladding. Laser cladding is a coating technology in which a laser beam is defocused on a substrate surface to produce a selected spot size. While the laser beam is defocused, a powder material is carried by an inert gas from a nozzle to the molten pool, either laterally or coaxially through the laser beam.
[0009] EP3006124 A1 discloses a laser cladding technique to coat steel rolls with work tool steel in order to improve thermal fatigue resistance and surface quality. The composition of the tool steel external coating mentioned in EP3006124 A1 is about 0.5-3.5% Carbon (C), 2-18% Chromium (Cr), 0.5-7% Molybdenum (Mo), 0.5-8% Vanadium (V), 0.2-5% Tungsten or Wolfram (W), 0-5% Niobium (Nb), 0-1% Titanium (Ti), 0.5-1% Manganese (Mn), 0.2-3% Silicon (Si) and 0-3% Nickel (Ni), the rest being Iron (Fe) and inevitable impurities.

OBJECTS OF THE DISCLOSURE
[0010] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0011] A general object of the present disclosure is to provide caster rolls, particularly intended for thin slab casting and rolling mills, which provides improved wear resistance at high temperature with respect to martensitic stainless steel.
[0012] An object of the present disclosure is to provide work rolls having a high-quality laser clad coating without cracks or porosities.
[0013] These and other objects and advantages of the present disclosure will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present disclosure is illustrated.

SUMMARY
[0014] This summary is provided to introduce concepts related to a laser clad and a caster roll having a roll substrate with said laser clad. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0015] The present disclosure relates to a laser clad comprising the following composition by weight: 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
[0016] In an aspect, the laser clad is supermartensitic with modified composition.
[0017] In an aspect, the laser clad comprising the following composition by weight: 0.01-0.03% Carbon (C), 2.5-3% Molybdenum (Mo), 4.2% Nickel (Ni), 4.6 Cobalt (Co), 0.3% Manganese (Mn), 12.35% Chromium (Cr), 0.6% Silicon (Si) and reminder being Iron (Fe).
[0018] The present disclosure further relates to a caster roll comprising a roll substrate with a laser clad, the caster roll comprising, by weight, 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
[0019] In an aspect, the roll substrate is a top zone roll strand.
[0020] In an aspect, the roll substrate comprises 0.18-0.23% Carbon (C), 0.56% Manganese (Mn), 12.7% Chromium (Cr), 0.25% Nickel (Ni), 0.045% Molybdenum (Mo), 0.009% Sulphur (S), 0.03% Phosphorus (P), 0.5% Silicon (Si), 0.08% Copper (Cu), 0.034% Vanadium (V), and the rest being Iron (Fe) and inevitable impurities.
[0021] In an aspect, the roll substrate diameter ranges from 130 mm to 150 mm.
[0022] The present disclosure further relates to a method for laser cladding on a caster roll. The method includes cleaning a roll substrate by machining the surface of the roll substrate; rotating the roll substrate around its axis of symmetry; forming a melt pool on the roll substrate using a laser beam; and feeding a laser clad in powder form into the melt pool using a coaxial nozzle to perform the laser cladding on the roll substrate, wherein the laser clad comprising, by weight, 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
[0023] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
[0025] FIG. 1 illustrates a schematic of a conventional continuous casting machine;
[0026] FIG. 2 illustrates a method for laser cladding on a caster roll, in accordance with an embodiment of the present disclosure;
[0027] FIG. 3 illustrates a diagram corresponding to high temperature wear resistance of coating and substrate; and
[0028] Fig 4A and 4B illustrate the microstructure of laser clad specimens obtained according to the present disclosure.

DETAILED DESCRIPTION
[0029] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0030] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0032] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0033] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0034] Embodiments and/or implementations described herein relate to a continuous caster roll which is able to better withstand the extremely harsh operating conditions in the continuous casting setup. In addition, the present disclosure is aimed to provide a laser clad having better wear resistance at such high temperatures. In an aspect, the laser clad proposed herein comprising the following composition by weight: 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
[0035] FIG. 2 illustrates an example method 200 for laser cladding on a caster roll, in accordance with an embodiment of the present disclosure. In particular, the method aims to provide a caster roll by laser cladding a martensitic stainless steel substrate with a metal coating having a supermartensitic stainless steel composition. The order in which the method 200 is described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the method 200, or an alternative method.
[0036] At block 202, the method 200 includes cleaning a roll substrate by machining the surface of the roll substrate.
[0037] At block 204, the method 200 includes rotating the roll substrate around its axis of symmetry.
[0038] At block 206, the method 200 includes forming a melt pool on the roll substrate using a laser beam.
[0039] At block 208, the method 200 includes feeding a laser clad in powder form into the melt pool using a coaxial nozzle to perform the laser cladding on the roll substrate, wherein the laser clad comprising, by weight, 0.01-0.03% Carbon (C), 0-0.04% Phosphorus (P), 0-0.02% Sulphur (S), 2.5-3% Molybdenum (Mo), 3.8-4.8% Nickel (Ni), 4-5.5 Cobalt (Co), 0.1-0.5% Manganese (Mn), 12-13.5% Chromium (Cr), 0.5-1% Silicon (Si) and reminder being Iron (Fe).
[0040] In a preferred aspect, the caster roll, in weight, comprises 0.18-0.23% Carbon (C), 0.56% Manganese (Mn), 12.7% Chromium (Cr), 0.25% Nickel (Ni), 0.045% Molybdenum (Mo), 0.009% Sulphur (S), 0.03% Phosphorus (P), 0.5% Silicon (Si), 0.08% Copper (Cu), 0.034% Vanadium (V), and the rest being Iron (Fe) and inevitable impurities.
[0041] In an aspect, the laser clad, or metal coating, is essentially a supermartensitic stainless steel with 4-5.5% Cobalt (Co) to improve the hot hardness of the coating of the laser clad.
[0042] Further, in an aspect, the diameter of the roll substrate can vary from 130-150 mm and may belong to segment 1 of the casting strand of a continuous casting machine.
[0043] Yet further, the laser clad, or metal coating, proposed herein may possess the following characteristics:
i. High metallurgical bonding,
ii. Low or no porosity in the clad along with finer microstructure because of high cooling rates,
iii. Homogenous composition,
iv. Coating thickness of 1.2 mm per layer,
v. Laser power of 1700 W to ensure complete melting of the powders and low dilution with the substrate,
vi. Scanning rate of 25 mm/s using a suitable cladding head with a coaxial nozzle, and
vii. Powder feed rate of 25-35 g/min to ensure efficient utilization of powder.
[0044] Further, in an alternative implementation, the laser clad, in weight, comprises a composition of 0.01% Carbon (C), 2.7% Molybdenum (Mo), 4.2% Nickel (Ni), 4.6% Cobalt (Co), 0.3% Manganese (Mn), 12.35% Chromium (Cr), 0.6% Silicon (Si), and reminder being Iron (Fe). Such composition for the laser clad showed that the quality of the bonding zone is very satisfactory in terms of cracks and porosities.
[0045] For example, with a composition of 0.01% Carbon (C), 2.7% Molybdenum (Mo), 4.2% Nickel (Ni), 4.6% Cobalt (Co), 0.3% Manganese (Mn), 12.35% Chromium (Cr), 0.6% Silicon (Si), and reminder being Iron (Fe), high temperature wear test at 400 °C showed that the laser clad was at least 2 times better than the base substrate in terms of wear resistance, as shown in FIG. 3.
[0046] One of the advantages of the laser clad composition proposed herein is that the laser clad or the metal coating achieved by laser cladding exhibits very fine martensitic microstructure strengthened by substitutional solid solution strengthening (FIGS. 4A and 4B).
[0047] Thus, the layer of the laser clad proposed herein deposited through a laser cladding procedure exhibit an improved high-temperature wear behaviour, a very good adherence to the surface, and a refined microstructure.
[0048] Furthermore, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0049] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0050] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.