Title of Invention

A PROCESS FOR MANUFACTURING WEAR RESISTANT LINERS FOR MATERIAL HANDLING EQUIPMENTS

Abstract

The present invention relates to the process for manufacturing heat treated high chromium iron alloy wear resistant liners for material handling equipments comprising the steps of liner material casting, preliminary grinding of the cast liner, testing of the surface of the cast liner material, final grinding wherein the said process is characterized by heat treatment cycle of the cast liner after the step of preliminary grinding followed by a final testing of surface of the liner after the final grinding process.

Full Text

2 FIELD OF THE INVENTION The present invention relates to a process for manufacturing wear resistant liners (alloy) for material handling equipments with improved life and better resistant to wear and impact and the alloy thereof. The material handling equipments requires a liner material that possesses a balance between the critical properties of wear resistance, good thermal stability and thorough hardening capability. Considering the above fact, a technology for manufacturing heat-treated alloyed material has been produced which shows improved wear resistance, good thermal stability and through hardening capability. The present innovation identifies the material composition and the method to produce it with an optimum combination of material characteristics that enables it to be used in a wide range of applications including liners for bunkers, hoppers, chutes, bins, railcars engaged in handling of materials like coke, sinter, iron ore. The liner material produced using the invented method offers substantially higher performances against the aggressive raw materials in terms of wear and impact These liners can successfully be used in for abrasion and erosion resistance under dry and slurry conditions in cement, mining and mineral processing industries. On investigation it has been established that the material cutting and ploughing occur due to continuous use of the liners under impact condition in handling the raw materials causing high adhesive and uneven abrasive wear of liners. Consequently, it is for this reason that most of the technology advances in materials compositions, material treatment and design are taking place. DESCRIPTION OF THE RELATED ART The liners used to protect the working surfaces of material handling equipments in steel industry are subjected to various kinds of attacks, such as wear, corrosion, impact. The choice of liner materials are governed by factors, such as 3 the application specific service requirements, ease of fabrication of a specific material in a specific form (shape, size and design). The materials used for lining application include Mn-steel, low alloy steel, martensitic stainless steel, alloy cast iron, composite plates, non-metallic materials (ceramics, UHMWP, Polyurethane, synthetic rubber, concrete). The basic problem with selection and use of liner materials lies with conflicting service requirements since the available materials and the processing techniques often offer a combination of material characteristics at the expense of each other. The presence of the high chromium in the steel alloy forms carbides, which increases wear resistance. The addition of molybdenum in the alloy increases its ability to get thorough hardened. The nickel contributes towards enhancing the impact resistance. Thermal stability refers to the ability of the material to maintain its heat-treated properties under the elevated temperatures experienced during service. A material with good thermal stability will maintain its hardness at elevated temperatures and be less susceptible to softening while in service. The liners wear by scratching of working surface because of continuous flow of raw materials resulting in loss of weight or volume. Under the impact condition, the cutting or ploughing also takes place resulting in removal of material from the working surface of liners. The resistance to wear is a direct function of the liner material, its hardness and microstructure. The ability of a liner to be through hardened is a positive attribute when considering overall performance. A thorough-hardened material has a consistent hardness throughout the cross-section and thus can be used to scrap size without re-hardening. SANKYU INC in a Japanese specification JP11207471A2 discloses wear resistant liner which improves a joining property with a steel base material at the 4 time of using a sintered hard alloy plate having an excellent wear resistance for a liner. The sintered hard alloy plate of 1-25 mm in thickness, a high chromium cast iron plate and a steel plate are laminated by diffusion joining wherein a thin sheet of copper or nickel is interposed in a boundary between the sintered hard alloy and the high chromium cast iron or copper is arranged in the sintered hard alloy side and nickel is arranged in the high chromium cast iron side. Whereby, the extreme wear resistance is displayed by the sintered hard alloy plate in the surface and the wear resistance is still maintained by the high chromium cast iron even in the case that the whole sintered hard alloy plate parts are wom or the sintered hard alloy plate is fallen down owing to a use for a long time. Therefore, a rapid damage caused by wear is prevented and the systematic maintenance working by a periodic inspection is allowed. Construction Forms. Inc. in an US specification US6467812 discloses Pipe having replaceable wear resistant lined coupler. A pipe section for concrete includes an end coupler interconnecting to another pipe section in a flow line. The coupler has an outer clamp secured extended from the pipe end with a coupling groove. An encircling clamp has sides located in the grooves of adjacent pipe sections to lock the pipe section together. The body and pipe end form an inner recess extending from the pipe end. An insert liner has a tubular portion matching the recess, with the outer surface of the tubular portion tapered to form a gap within the recess. The insert liner has an outer flange matching the outer diameter of the body and abuts the body. The inner wall of the liner has a central transition point from which the wall tapers inwardly in opposite directions to the outer end. The body member is formed of high strength ductile steel. The insert liner is formed of a wear resistant material having a Rockwell hardness of 80 to 90. A carbide alloy consisting essentially of carbides , martensite, bainite and austenite, and 12-15% chromium, 2-3% carbon and traces nickel, molybdenum and austenite. A toughened ceramic is disclosed. The liner is adhesively bonded to the body using an epoxy adhesive, which is responsive to heat for release of the liner. The liner is inserted by applying adhesive on the tubular portion and then pushing the liner into the recess. 5 Hotger Michael in an US specification US20040067384 discloses sliding pair used for piston-cylinder arrangements in steam motors comprises a first sliding element, preferably a piston or piston ring, made of a carbon material and a second sliding element, preferably a cylinder or guide bush. The invention relates to pairs of sliding elements for machine parts exposed to high-pressure and high- temperature steam, preferably piston-cylinder arrangements for steam engines. Here, the pairs of sliding elements consist of a first sliding element which has been produced from a synthetic, fired but not graphitized carbon material which comprises graphitized carbon black and/or natural graphite as significant filler and whose pores are filled with metal, a metal alloy, a ceramic, a synthetic resin and/or pitch which has been carbonized, preferably in the form of a piston and/or piston ring, and a second sliding element, preferably in the form of a cylinder liner or guide bush, comprising an iron-containing, high-temperature-resistant material which is preferably alloyed with chromium and/or nickel and is provided at least on the surface layer with a nitride layer, a light metal alloy, a material which has been produced by a powder-metallurgical route and comprises iron or steel and titanium carbides, a ceramic composite, a carbon material which consists of or consists essentially of graphite or a cemented hard material or a material provided with a sliding layer of cemented hard material. The pairs of sliding elements according to the invention display low wear, in particular even when exposed to supercritical steam and preferably also when exposed to liquid water. From the above discussion it becomes obvious that the liner application requires a new and improved material that possesses a balance between the critical properties of wear resistance, good thermal stability and through-hardening capability. 6 SUMMARY OF THE INVENTION Considering the above fact, it is an object of the present invention to provide an improved process for manufacturing heat treated alloyed wear resistant liner material having improved wear resistance, good thermal stability and through hardening capability which contains a relatively low level of expensive alloying ingredients and also an improved heat treated alloyed liner composition thereof. The heat-treated alloyed liner composition of the present invention possesses a balance between the critical properties of wear resistance, good thermal stability and through hardening capability. Therefore, according to the present invention, there is provided a process for manufacturing heat treated alloyed wear resistant liners for material handling equipments comprising the steps such as liner material casting; guiding solidification in casting; preliminary grinding of the cast liner; testing of the surface of the cast liner material; final machining and grinding wherein the said process is characterized by heat treatment cycle of the cast high chromium iron alloy after the step of preliminary grinding followed by a final testing of surface of the shell after the final grinding process. Also, there is provided a method of preparation of heat treated alloyed wear resistant liners for material handling equipments as claimed in claim 1, wherein the said alloy consist essentially of in weight percent, about 2.0% to 2.5% carbon, 1.5% (maximum) silicon, from 0.5% to about 1.5% manganese, about 0.06% maximum phosphorus, about 0.1% maximum sulphur, from 20% to about 25% chromium, from 1.0% to about 1.5% each of nickel and molybdenum and balance essentially iron, moreover, an alloy having the aforesaid composition. 7 The elements carbon, silicon, sulphur, phosphorous, manganese, chromium, nickel, molybdenum and the balance there between, are critical in every sense. In the improved embodiment having superior wear resistance, good thermal stability and through hardening capability, the ranges of these elements are critical. Omission of one of the elements, or departure of any of these critical elements from the ranges set forth above results in loss in one or more of the desired properties. The liner material is expected to possess the following unique properties, which are ideal for the liners for material handling: • High chromium alloys are highly wear resistant • The tempered martensitic matrix contributes to overall strength and toughness, as well as providing an increased hardness for resisting wear. • This material maintains the through hardening capability and excellent thermal stability. Accordingly, it is a principal object of the invention to manufacture a wear resistant liner (alloy) for use in material handling equipments. Another object of the present invention is to devise a process to manufacture a wear resistant liner for use in material handling equipments. To accomplish the principle objective of the invention the constituents of the liner material are so designed so that following characteristics can be achieved which are ideal for a liner material. a) Wear resistance. b) Thermal stability. c) Resistance to impact. 8 The different objectives for an ideal liner (alloy) is achieved with experiments carried out at RDCIS laboratory. The liner material produced under the current invention has successfully been used in coke weighing hoppers of blast furnace and it was found that the developed liner has 3 to 4 times superior performance compared to commonly used liner materials for such applications. It is yet another objective of the present invention to set out a process of hardening and tempering of the shell to achieve the desired results. It is yet another object of the invention to provide the alloyed liner material leads to an appreciable economy in cost of production due to extended working life of the liner. These and other objects of the present invention will become readily apparent upon further review of the following specification BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a flowchart for the manufacture of the liner; Fig. 2 is a chart showing the weight of different constituents of the alloy in percentage; Fig. 3(a) shows a microstructure having discontinuous network of primary (M7C) Carbide (PC) + austenite (as cast); Fig. 3(b) shows a microstructure having (PC) + martensite (as quenched); Fig. 3(c) shows a microstructure having (PC) + tempered martensite (as quenched and tempered); 9 DETAILED DESCRIPTION OF THE INVENTION The liner is a cast iron, alloyed with carbon, chromium, nickel, molybdenum, manganese, silicon, phosphorus and sulphur. The selected alloys are present within the iron at levels that provide a balance between carbide formations and generation of a tough matrix. The chemistry contains enough alloys to allow for thorough hardening of the standard thickness of the liner designs. The composition and microstructure dictate the properties of the heat-treated alloyed liner material. The microstructure of liner material consists of discontinuous network of primary carbides, and a tempered martensitic matrix. Although each of the constituents of the microstructure affects all of the properties, each affects certain properties more than others do. The tempered martensitic matrix provides the basic strength and hardness of the alloyed cast iron liner material. The wear resistance is aided by the carbide content and distribution. The preferred process technology for manufacturing heat treated alloyed liner with improved life which is suitable for use in material handling equipments, composition exhibiting superior wear resistance, good thermal stability and through hardening capability, consists essentially of, in weight percent, about 2.0 to 2.5% carbon, 1.50% (max) silicon, from 0.5% to about 1.5% manganese, about 0.06% maximum phosphorus, about 0.10% maximum sulphur, from 20.0% to about 25.0% chromium, from 1.0% to about 1.5% nickel and molybdenum and balance essentially iron. In turn, this microsrtucture establishes the properties that enable the heat-treated alloyed cast iron liner material to perform well in the material handling equipments. 10 The wear resistance of the alloy material could have been improved by increasing the amount of primary carbides in the matrix. Increasing the cooling rate after casting can orient the primary carbides in a manner that can further improve the wear resistance and impact properties. A high concentration of the carbides at the boundaries would decrease the overall toughness of the material by promoting brittle fracture along the boundaries under impact loading. The chemical composition as described earlier is melted in electric furnace, and then typically static cast into a shell moulding. Shell moulding is a variation of sand moulding in which the mould is formed of a thin layer or shell of a special type of sand. The shell is formed by coating a hot metal pattern with resin impregnated sand. The heat melts the resin, which then holds the grains of sand together forming a shell. The shell is formed by coating a hot metal pattern with resin impregnated sand. The heat melts the resin, which then holds the grains of sand together forming a shell. Shelf molding is also similar to sand molding except that a mixture of sand and 3- 6% resin holds the grains together. Set-up and production of shell mold patterns takes weeks, after which an output of 5-50 pieces/hr-mold is attainable. Aluminium and magnesium products average about 13.5 kg as a normal limit, but it is possible to cast items in the 45-90 kg range. Shell mold walling varies from 3-10 mm thick, depending on the forming time of the resin. The different stages in shell mold processing includes: 1. initially preparing a metal-matched plate 2. mixing resin and sand 3. heating pattern, usually to between 505-550 K 4. investing the pattern (the sand is at one end of a box and the pattern at the other, and the box is inverted for a time determined by the desired thickness of the mill) 5. curing shell and baking it 6. removing investment 11 7. inserting cores 8. repeating for other half 9. assembling mold with graphite lining 10. pouring mold (1350 - 1400ºC) 11. Guiding solidification (Optional) - The solidification pattern may be guided using the metallic mould to produce a particular morphology of carbides which would further be improving the properties of the liner material. The inocultation of carbides may also be incorporated in the mould during pouring to further enhance the wear resistance without impairing the impact resistance. 12 removing casting 13. cleaning and trimming/ frettling The mould is then taken out and preliminary grinding is carried out as per the requirement and the dimensions. The most important operation used in the process of making liners for the material handling equipments is heat treatment cycle. The treatment cycle consists of 3 steps, which is annealing, quenching and tampering. The annealing is carried over the said cast alloy liner by placing the liner in a furnace. The loading temperature of the liner and furnace is room temperature. The furnace is heated at the rate of 2 degree Celsius/min (max) to a temperature of 760 to 780 degrees Celsius. The soaking time for the shell at soaking temperature is around 2 hrs inside the furnace at around 760 degree Celsius. The temperature has a marked effect on microstructure and on mechanical properties such as hardness and tensile strength. Furnace cooling of the liner is being carried out to 250 degree Celsius and followed by air-cooling to room temperature. Shot blasting operation is being carried out in order to clean the surface of the castings after the annealing process. Air/oil quenching is used for cooling the hardened alloy liners. The quenching process is initiated by charging the liner to 250 degree Celsius followed by heating the liner at the rate of 2 degree Celsius/min (max) to a temperature of 650 degrees Celsius. The soaking time for the shell at soaking temperature is 12 around 2 hrs inside the furnace at same temperature. The liner is again heated to 850 degree Celsius at the rate of 2 degree Celsius/min and thereby soaking for around 1 hour at same temperature. The alloyed liner is again repeatedly heated to 1010 degree Celsius at the rate of 4-5 degree Celsius/min and thereby soaking for around 30 minutes at same temperature. Air or oil quenching is then carried out as per the requirement or facility provided. For oil quenching the prepared liner is dipped in the oil and for air quenching the liner is cooled in natural air so that the required properties are developed. Tempering is done immediately after quench hardening. When the steel cools to about 40 ºC after quenching, it is ready to be tempered. After quenching, castings are usually tempered at temperatures well below the transformation range for about 1h per inch of thickest section. As the quenched iron is tempered, its hardness decreases, whereas it usually gains in strength and toughness. Herein the hardened liners are is tempered by heating the liners from room temperature to a temperature of 470 degree Celsius (460-480 degree Celsius) at a rate of 2 degree Celsius/min (max). Here also the soaking time for the hardened liners at soaking temperature is a round 3 hrs. The cooling of the liners is done outside the furnace in natural air to room temperature. The pre- tempered liner is again reheated from room temperature to a temperature of 400 degree Celsius (400-420 degree Celsius) at a rate of 2 degree Celsius/min (max). Here also the soaking time for the hardened shell at soaking temperature is around 3 hrs. The cooling of the shell is done outside the furnace by forced air to room temperature. The liners are hardened and tempered to improve their mechanical properties, particularly strength and wear resistance. After being quenched and tempered, the hardness is made to an average of 53-55 HRC. The hardened irons usually exhibit wear resistance approximately five times greater than that of Mn-steel liners. The hardness of the liner measure after cast is 44-45 HRC and 56-58 HRC after quenching. Further, the micro-hardness achieved for the primary carbide is 965 to 1120 HV and 500 to 600 HV for the final matrix. 13 The liners are then subjected to a machining and grinding process, which removes the effects hardening and tampering, and ensures a flat surface. The purpose of grinding is to lessen the depth of deformed metal to a point. Belt, disk, and surface grinders, cylindrical grinders can be used which further uses abrasives bonded to a surface and the final dimensions are achieved as per the drawings. After machining and grinding the shell is subjected to ultrasonic testing for a second time. Ultrasonic testing (UT) is one of the most widely used techniques for discontinuity detection and material characterization in various engineering fields. The advantages of UT as compared to other nondestructive techniques for metal tests are higher penetration, higher sensitivity and greater accuracy. The iron based materials exhibit good thermal properties. The wear resistance is good due to the presence of the primary carbides. The low as-cast hardness of the high chromium iron alloy can limit the wear resistance of the material. Chemical composition is an important parameter influencing the heat treatment of high chromium irons. Manganese, nickel, and molybdenum are the recognized elements for increasing the hardenability of high chromium iron. Although chromium, by itself, does not influence the hardenability of high chromium irons, its contribution to carbide stabilization is important. The above-described embodiments of the invention are intended to be examples of the present invention. Numerous modifications, changes and improvements within the scope of the invention will occur to the reader. Those of skill in the art may effect alterations and modifications thereto, without departing from the scope of the invention, which is defined solely by the claims appended hereto. 14 We claim: 1. The process for manufacturing heat treated high chromium iron alloy wear resistant liners for material handling equipments comprising the steps of: liner material casting; preliminary grinding of the cast liner; testing of the surface of the cast liner material; final grinding wherein the said process is characterized by heat treatment cycle of the cast liner after the step of preliminary grinding followed by a final testing of surface of the liner after the final grinding process. 2. The process as claimed in claim 1, wherein the said heat treatment cycle is characterized by processes of annealing, quenching and tempering of the cast liner. 3. The process as claimed in claim 2, wherein the annealing process includes heating the ground liner shell in a furnace with charging temperature as room temperature. 4. The process as claimed in claim 3, wherein the furnace is heated at the rate of 2 degree Celsius per minute (max). 5. The process as claimed in claim 3, wherein the soaking temperature of the cast liner in the furnace is 760 degree Celsius and the soaking time is 2 hours. 6. The process as claimed in claim 3, wherein the cast liner is cooled in the furnace to 250 degree Celsius and then followed by air cooling. 15 7. The process as claimed in claim 2, wherein the quenching process includes heating the annealed finer in a furnace with charging temperature as 250 degree Celsius followed by heating to 650 degree Celsius at the rate of 2 degree Celsius per minute (max). 8. The process as claimed in claim 7, wherein the soaking temperature of the annealed cast finer in the furnace is 650 degree Celsius and the soaking time is 2 hours followed by reheating to 850 degree Celsius at the rate of 2 degree Celsius per minute (maximum). 9. The process as claimed in claim 8 wherein the second soaking temperature of the annealed cast liner in the furnace is 850 degree Celsius and the soaking time is 1 hours followed by reheating to 1000 to 1020 degree Celsius at the rate of 4 to 5 degree Celsius per minute (maximum). 10. The process as claimed in claim 9 wherein the third soaking temperature of the annealed cast liner in the furnace is 1010 degree Celsius and the soaking time is 30 minutes followed by cooling. 11. The process as claimed in claim 10, wherein the annealed cast liner is cooled to room temperature in natural air or by oil. 12. The process as claimed in claim 2, wherein the tempering process includes heating the ground cast liner in a furnace with loading temperature as room temperature followed by heating to 460 to 480 degree Celsius. 13. The process as claimed in claim 12, wherein the soaking temperature of the quenched cast finer in the furnace is 470 degree Celsius and the 16 soaking time is 3 hours followed by cooling in natural air to room temperature. 14. The process as claimed in claim 13, wherein the quenched and tempered cast liner is reheated in the furnace to 400 to 420 degree Celsius followed by soaking at 400 degree Celsius and the soaking time is 3 hours cooling in natural air to room temperature. 15. The process as claimed in claim 2, wherein the said heat treatment cycle produces a hardness of 53 to 55 HRC with micro-hardness in the range of 985 to 1120 HV (Primary Carbide) and 500 to 600 HV (final matrix). 16. The process as claimed in claim 1, wherein the testing for the liner surface is carried out using process of ultrasonic testing. 17. The method of preparation of heat treated high chromium iron alloy wear resistant liners for material handling equipments as claimed in claim 1, wherein the said alloy consist essentially of, in weight percent, about 2.0% to 2.5% carbon, from 1.5% (maximum) silicon, from 0.5% to about 1.5% manganese, about 0.06% maximum phosphorus, about 0.1% maximum sulphur, from 20% to about 25% chromium, from 1.0% to about 1.5% each of nickel and molybdenum and balance essentially iron. 18. The heat treated high chromium iron alloy wear resistant liners consist essentially of, in weight percent, about 2.0% to 2.5% carton, from 1.5% (maximum) silicon, from 0.5% to about 1.5% manganese, about 0.06% maximum phosphorus, about 0.1% maximum sulphur, from 20% to about 25% chromium, from 1.0% to about 1.5% each of nickel and molybdenum and balance essentially iron. 17 19. The process for manufacturing heat-treated high chromium iron alloy wear resistant liners for material handling, substantially as herein described with particular reference to the accompanying drawings. 20. The method for preparation of heat-treated high chromium iron alloy wear resistant liners for material handling, substantially as herein described with particular reference to the accompanying drawings. 21. The heat-treated high chromium iron alloy wear resistant liners for material handling, substantially as herein described with particular reference to the accompanying drawings. The present invention relates to the process for manufacturing heat treated high chromium iron alloy wear resistant liners for material handling equipments comprising the steps of liner material casting, preliminary grinding of the cast liner, testing of the surface of the cast liner material, final grinding wherein the said process is characterized by heat treatment cycle of the cast liner after the step of preliminary grinding followed by a final testing of surface of the liner after the final grinding process.

Documents:

00212-kol-2006-abstract.pdf

00212-kol-2006-claims.pdf

00212-kol-2006-description complete.pdf

00212-kol-2006-drawings.pdf

00212-kol-2006-form 1.pdf

00212-kol-2006-form 2.pdf

00212-kol-2006-form 3.pdf

212-KOL-2006-(18-01-2013)-CORRESPONDENCE.pdf

212-KOL-2006-(18-01-2013)-OTHERS.pdf

212-KOL-2006-(20-03-2014)-CLAIMS.pdf

212-KOL-2006-(20-03-2014)-CORRESPONDENCE.pdf

212-KOL-2006-(20-03-2014)-DESCRIPTION (COMPLETE).pdf

212-KOL-2006-(20-03-2014)-DRAWINGS.pdf

212-KOL-2006-(20-03-2014)-FORM-1.pdf

212-KOL-2006-(20-03-2014)-FORM-2.pdf

212-KOL-2006-(20-03-2014)-OTHERS.pdf

212-KOL-2006-(29-11-2011)-CORRESPONDENCE.pdf

212-KOL-2006-(29-11-2011)-OTHERS.pdf

abstract-00212-kol-2006.jpg