Part of a tracked vehicle, undercarriage assembly of a tracked vehicle comprising said part, tracked vehicle comprising said part and process for producing said part of a tracked vehicle

Abstract

A part of a tracked vehicle (1), for example of an undercarriage assembly (30A, 30B) of a tracked vehicle according to the present invention is made of a steel having one or more of the following features: -a content of carbon comprised between 0,1-0,7 %wt; -a content of manganese comprised between 0,6-2 % wt; -a content of silicon equal to or lower than 1,3 % wt -a content of chromium equal to or lower than 0,8 % wt -a content of sulfur equal to or lower than 0,1 % wt -a content of phosphorus equal to or lower than 0,05 % wt; -a content of molybdenum equal to or lower than 0,13 % wt -a content of nitrogen equal to or lower than 0,04 % wt -a content of niobium equal to or lower than 0,07 % wt -a content of vanadium equal to or lower than 0,4 % wt.

Description

PART OF A TRACKED VEHICLE , UNDERCARRIAGE ASSEMBLY OF A TRACKED VEHICLE COMPRIS ING SAID PART , TRACKED VEHICLE COMPRIS ING SAID PART AND PROCESS FOR PRODUCING SAID PART OF A TRACKED VEHICLEField of the invention

[0001] The present invention relates to a part of tracked vehicle , such as the retaining collar of a roller assembly of a compact track loader, and a process for manufacturing said part .Background art

[0002] Collars of rollers and idlers in a tracked vehicle for earth moving machines , especially in the so-called Compact Track Loaders , are usually made o f quenched and tempered forged steel .

[0003] The author / authors of the present invention deem this known production process relatively expensive in terms of time and money .

[0004] A scope of the present invention is overcoming the above described drawbacks of the state of the art and in particular providing a vehicle part and a process for producing it which is less expensive in regard of time and money in comparison with the parts and manufacturing processes of the state of the art .Summary of the invention

[0005] This scope is achieved, according to a first aspect of the present invention, with a part of a tracked vehicle having the features according to claim 1 .

[0006] In a particular embodiment of the invention, said part of tracked vehicle is made of a steel having one or more of the following features :-a content of carbon comprised between 0 , 15-0 , 5 %wt ;-a content of manganese comprised between 1-2 % wt;-a content of silicon comprised between 0,05-1 % wt-a content of chromium equal to or lower than 0,6 % wt -a content of sulfur comprised between 0,01-0,08 % wt -a content of phosphorus equal to or lower than 0,04 % wt-a content of molybdenum equal to or lower than 0,1 % wt -a content of nitrogen equal to or lower than 0,03 % wt -a content of vanadium equal to or lower than 0,3 % wt; -a content of titanium equal to or lower than 0,001% wt or 0, 006 % wt .[7] In a particular embodiment of the invention, said part of tracked vehicle is made of a steel having one or more of the following features:-a content of carbon comprised between 0,4-0, 5 %wt;-a content of manganese comprised between 1-1,8 % wt;-a content of silicon comprised between 0,1-0, 9 % wt-a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,015-0,07 % wt -a content of phosphorus equal to or lower than 0,035 % wt-a content of molybdenum equal to or lower than 0,09 % wt-a content of nitrogen comprised between 0,005-0,03 % wt -a content of vanadium comprised between 0,05-0,3 % wt .[8] In a particular embodiment of the invention, said part of tracked vehicle is made of a steel having one or more of the following features:-a content of carbon comprised between 0,42-0,49 %wt;-a content of manganese comprised between 1,2-1, 6 % wt;-a content of silicon comprised between 0,15-0,8 % wt -a content of chromium equal to or lower than 0,3 % wt-a content of sulfur comprised between 0,02-0,06 % wt -a content of phosphorus equal to or lower than 0,025 % wt-a content of molybdenum equal to or lower than 0,08 % wt-a content of nitrogen comprised between 0,01-0,02 % wt -a content of vanadium comprised between 0,08-0,2 % wt .[9] In a particular embodiment of the invention, said part of tracked vehicle is made of a steel having one or more of the following features:-a content of carbon comprised between 0,43-0,47 %wt; -a content of manganese comprised between 1,3-1, 5 % wt; -a content of silicon comprised between 0,3-0, 6 % wt -a content of chromium equal to or lower than 0,2 % wt; -a content of sulfur comprised between 0,03-0,05 % wt -a content of phosphorus equal to or lower than 0,015 % wt ;-a content of molybdenum equal to or lower than 0,06 % wt-a content of nitrogen comprised between 0,01-0,016 % wt -a content of vanadium comprised between 0,1-0,17 % wt .

[0010] The compositions of the steel previously described allow a part of a tracked vehicle to undergo heat treatments lacking quenching or tempering through cooling liquids, for example through immersion in liquid baths; on the contrary the mechanical parts having the previously described composition can be successfully cooled in air after forging or other hot forming operations, saving time and reducing costs and reducing environmental pollution, since there are no heat treating liquids to be disposed.

[0011] The steel of a finished part of a tracked vehicleso obtained has a finer grain and hence the same or better mechanical features, such as mechanical resistance and hardness, than those of steel hardened and tempered with heat treatment liquids.

[0012] In a particular embodiment of the invention, said part of tracked vehicle is chosen from the following set of parts of an undercarriage assembly of said tracked vehicle (1) : a retaining collar (382) for example for a compact track loader roller assembly (38) , a retaining collar (387) for rotatably fixing an idle wheel (36) for example of a compact track loader roller assembly (38) , an annular collar having a diameter comprised between 35-200 millimetres and / or an average of maximum thickness comprised between 15-100 millimetres, an idle wheel (36) configured for rolling over or under a continuous crawler track of said undercarriage, a driving wheel (34) configured for engaging with, rolling over or under or driving a continuous crawler track of said undercarriage, a side subassemblies (30A, 30B) , a pin, a shaft or other parts of the crawler track (32) of said undercarriage assembly, a track shoe, a roller body (380) , a roller shaft (381) , an idle wheel retaining collar (387) , an idle wheel shafts (385) , a shafts having an overall length comprised between 100-350 millimetres and / or a maximum or average diameter comprised between 10-100 millimetres, a metal plate or shell having an average or maximum thickness for example comprised between 2-30 millimetres, a roller, a toothed wheel, a wheel, a ring, a bushing wherein said parts have one ormore of the following dimensions:-an axial length comprised between 50-400 millimetres;-a maximum or average diameter comprised between 5-100 millimetres ;-a maximum or average thickness comprised between 10-500 millimetres .

[0013] The previously described steel compositions are particularly suitable for making these undercarriage parts, simplifying their manufacturing process, reducing their production costs and at the same time enhancing their hardness, wear resistance and other mechanical features .

[0014] In a particular embodiment of the invention, said part of tracked vehicle is obtained through a manufacturing process comprising the following steps:5.7.1) obtaining a semi-manufactured part by forging or machining;5.7.2) bringing or maintaining the semi-manufactured part at a temperature equal to or higher than 1000°C and or sufficient to austenitize at least 80% of the steel of said tracked vehicle part;5.7.3) cooling the semimanufactured part in air;-obtaining the final undercarriage part from the cooled semimanufactured part.

[0015] In a particular embodiment of the invention, said part of tracked vehicle has one or more of the following features :-a grain equal to or greater than 5, according to ASTM norms ;-a final hardness comprised between 250-400 HB (Brinell Hardness ) ;-a tensile strength at rupture (RM) comprised between 800-1400 MPa;-a 0.2% offset yield strength (RP0.2) comprised between 450-750 MPa.

[0016] According to a second aspect of the present invention this scope is achieved with an undercarriage assembly having the features according to claim 9.

[0017] In a particular embodiment of the invention, said undercarriage assembly comprises one of more of the following parts or assemblies: a continuous crawler track (32) , an undercarriage frame (33) , a driving wheel (34) , one or more idle wheels (36) and a plurality of roller assemblies (38) .

[0018] According to a third aspect of the present invention this scope is achieved with a tracked vehicle having the features according to claim 11.

[0019] In a particular embodiment of the invention, said tracked vehicle (1) is chosen from the following set: a bulldozer, excavator, grader, mobile drill, tractor, crawler, tank, heavy equipment vehicle, a earthmoving machine, a vehicle to be used for example in mining, heavy constructions, demolition and waste disposal.

[0020] These vehicles are particularly suitable for including parts made of -or however containing- the steel compositions previously described.

[0021] According to a fourth aspect of the present invention this scope is achieved with a process having the features according to claim 13.

[0022] In a process according to a particular embodiment of the invention, after step S.13.2) the cooled forged semimanufactured part is machined without being treated with quenching and tempering in a heat treatment liquidbefore being machined.

[0023] In a process according to a particular embodiment of the invention, in step S.13.2) the semi-manufactured part is brought or maintained at a temperature comprised between 1180-1230°C.

[0024] In a process according to a particular embodiment of the invention, in step S.13.3) the semimanufactured part is cooled down to a temperature equal to or lower than 900°C.

[0025] In a process according to a particular embodiment of the invention, in step S.13.3) the semimanufactured part is cooled down to a temperature comprised between 600-700°C through forced thermal convection.

[0026] In a process according to a particular embodiment of the invention, in step S.13.3) the semimanufactured part is cooled down to a temperature comprised between -20°C and 40°C and eventually equal to or lower than 25°C, and said cooling between 600°C and 40°C is carried out through natural thermal convection.

[0027] The previous processes form f erric / pearlit ic finegrained structures in the steel, in the absence of bainite and martensite, allowing to achieve the above mentioned hardness and strength values at lower manufacturing costs than those of currently known manufacturing processes.

[0028] Further advantages which can be achieved with the present invention will appear more evident for the skilled reader, from the following detailed description of a particular and non limiting embodiment, described with reference to the following schematic figures.List of FiguresFigure 1 shows a perspective view of a compact trackedloader according to a particular embodiment of the present invention;Figure 2 shows a perspective view of the undercarriage assembly of the compact tracked loader of Figure 1 ;Figure 2A shows a perspective view of a roller assembly of the undercarriage assembly of Figure 2 ;Figure 2B shows a perspective view of a collar of the roller assembly of Figure 2B or of the idler assembly of Figure 3 ;Figure 2C shows an exploded perspective view of the roller assembly of Figure 2A;Figure 3 shows a perspective view of an idle wheel assembly of the compact tracked loader of Figure 1 .Detailed description

[0029] Figures 1-3 relate to a compact tracker loader, referred to as with the overall reference 1 , according to a particular embodiment of the present invention .

[0030] The compact tracked loader 1 can comprise an undercarriage assembly 3, a chassis 5 forming a driver ' s cab 7 and a dozer blade 9.

[0031] The blade 9 can be driven by one or more mechanical arms 11 .

[0032] The undercarriage assembly 3 can comprise one or more -two in the embodiment of Figure 1- side subassembly 30A, 30B each of which in its turn can comprise a continuous crawler track 32 , an undercarriage frame 33, a driving wheel 34 , one or more - for example two- idle wheels 36 and a plurality of roller assemblies 38 .

[0033] The continuous crawler track 32 can be made for example mostly of rubber or another elastomeric material - for example as an annular belt of rubber or elastomeric material- or mostly made of metal parts , for examplecomprising a plurality of links articulated together so as to form an annular chain, wherein said links are for example made of steel or other metals ; said links can be connected together and articulated for example through suitable pins .

[0034] The driving wheel 34 is configured for engaging with the internal side of a respective continuous crawler track 32 and driving said crawler track 32 , for example causing the latter to slide or more generally run relative to the chassis 5 .

[0035] The driving wheel 34 , each idle wheel 36 and each roller assembly 38 can be fixed to the undercarriage frame 33.

[0036] The undercarriage frame 33 can have an oblong overall shape ( Figure 2 ) and / or be shaped substantial ly as a beam ( Figure 2 ) .

[0037] The driving wheel 34 , each idle wheel 36 and each roller assembly 38 is configured for rolling over or under the internal side of a respective continuous crawler track 32 .

[0038] The compact tracked loader 1 preferably comprise at least one internal combustion engine (not shown) and / or one or more electric or hydraulic motors (not shown) for driving each driving wheel 32 and more generally powering the continuous tracks 32 , the undercarriage assembly 3, the blade 9, mechanical arms 11 and the tracked loader 1 in general .

[0039] Each roller assembly 38 can comprise a roller body 380 , a roller shaft 381 and a retaining collar 382 ( Figure 2A, 2B, 2C ) .

[0040] The roller body 380 can form an outer surface preferably having the overall shape of a surface orrevolution and during the normal operation is configured for turning about itsel f , the roller shaft 381 and a rotation axis AR ( Figure 2A) .

[0041] The roller body 380 and the roller shaft 381 are preferably coaxial with the axis AR ( Figure 2A) .

[0042] The roller body 380 preferably forms an internal through hole or cavity (not shown) substantially coaxial with the rotation axis AR.

[0043] Each retaining collar 382 preferably has an overall ring shape forming a central through hole 384 , for example the overall shape of a relatively thick disc ( Figure 2B ) .

[0044] Each retaining collar 382 preferably axially f ixes the respective roller body 380 to the respective roller shaft 381 .

[0045] To this end the roller shaft 381 can extend through the internal through hole or cavity of the roller body 380 and through the central through hole 384 of the respective retaining collar 382 , preferably protruding out of the latter ( Figure 2B ) ; the retaining collar 382 can be axially fixed to the roller shaft 381 through a circlip 386 or another retaining ring or fastening .

[0046] The retaining collar 382 has preferably a substantially annular shape , has preferably a diameter comprised between 35-180 millimetres , between 50-135 millimetres or between 70-90 millimetres and / or an average or maximum thickness , measured in an axial direction, preferably comprised between 15-80 millimetres , between 20-60 millimetres or between 30-40 millimetres .

[0047] According to an aspect of the present invention,the retaining collar 382 or another part of the undercarriage assembly 3 or more generally of a tracked vehicle, such as the compact tracker loader 1, are made of a steel having one or more of the following features: -a content of carbon comprised between 0,1-0, 7 %wt;-a content of manganese comprised between 0,6-2 % wt;-a content of silicon equal to or lower than 1,3 % wt -a content of chromium equal to or lower than 0,8 % wt -a content of sulfur equal to or lower than 0,1 % wt -a content of phosphorus equal to or lower than 0,05 % wt ;-a content of molybdenum equal to or lower than 0,13 % wt-a content of nitrogen equal to or lower than 0,04 % wt -a content of niobium equal to or lower than 0,5 % wt, possibly equal to or lower than 0,07 % wt, more preferably comprised between 0,05-0,2 % wt;-a content of vanadium equal to or lower than 0,5 % wt, eventually equal to or lower than 0,4 % wt2, possibly comprised between 0,05-0,2 % wt;-wherein said contents are the weight percent of the corresponding substance.

[0048] Preferably said steel has one or more of the following features:-a content of carbon comprised between 0,15-0,5 %wt;-a content of manganese comprised between 1-2 % wt;-a content of silicon comprised between 0,05-1 % wt-a content of chromium equal to or lower than 0,6 % wt -a content of sulfur comprised between 0,01-0,08 % wt -a content of phosphorus equal to or lower than 0,04 % wt-a content of molybdenum equal to or lower than 0,1 % wt-a content of nitrogen equal to or lower than 0,03 % wt-a content of vanadium equal to or lower than 0,3 % wt;-a content of titanium equal to or lower thanOT

[0049] More preferably said steel has one or more of the following features:-a content of carbon comprised between 0,4-0, 5 %wt;-a content of manganese comprised between 1-1,8 % wt;-a content of silicon comprised between 0,1-0, 9 % wt-a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,015-0,07 % wt -a content of phosphorus equal to or lower than 0,035 % wt-a content of molybdenum equal to or lower than 0,09 % wt-a content of nitrogen comprised between 0,005-0,03 % wt -a content of vanadium comprised between 0,05-0,3 % wt .

[0050] More preferably said steel has one or more of the following features:-a content of carbon comprised between 0,42-0,49 %wt;-a content of manganese comprised between 1,2-1, 6 % wt;-a content of silicon comprised between 0,15-0,8 % wt -a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,02-0,06 % wt -a content of phosphorus equal to or lower than 0,025 % wt-a content of molybdenum equal to or lower than 0,08 % wt-a content of nitrogen comprised between 0,01-0,02 % wt -a content of vanadium comprised between 0,08-0,2 % wt .

[0051] Even more preferably said steel has one or more of the following features:-a content of carbon comprised between 0,43-0,47 %wt;-a content of manganese comprised between 1,3-1, 5 % wt;-a content of silicon comprised between 0,3-0, 6 % wt-a content of chromium equal to or lower than 0,2 % wt or 0,1 % wt;-a content of sulfur comprised between 0,03-0,05 % wt-a content of phosphorus equal to or lower than 0,015 % wt-a content of molybdenum equal to or lower than 0,06 % wt-a content of nitrogen comprised between 0,01-0,016 % wt -a content of vanadium comprised between 0,1-0,17 % wt .

[0052] More preferably said steel contains all of the following elements, preferably in the above mentioned amounts: carbon, manganese, silicon, chromium, sulfur, phosphorus, vanadium, nitrogen, molybdenum.

[0053] Preferably said steel contains substantially no boron or a boron content equal to or lower than 0,0001- 0, 0005 % wt .

[0054] Preferably the retaining collar 382 or another tracked vehicle part, and in particular the steel which is made of, has one or more -and preferably all of them- of the following features, preferably determined according to UNI EN ISO 6892-1 or ASTM E112:-a grain equal to or greater than 5, according to ASTM norms ;-a final hardness comprised between 250-400 HB (Brinell Hardness) or 280-340 HB;-a tensile strength at rupture (RM) comprised between 800-1400 MPa or 900-1000 MPa;-a 0.2% offset yield strength (RP0.2) comprised between 450-750 MPa or 550-650 MPa.

[0055] In a second aspect the present invention relates to a process for producing a part of a tracked vehicle, for example the retaining collar 382 or another part of a tracked vehicle or of an undercarriage assembly of a tracked vehicle, comprising the following steps:5.1) -obtaining a semi-manufactured part by forging or machining, wherein the semi-manufactured part is made of a steel having the previously mentioned features, for example the above mentioned compositions;5.2) -bringing or maintaining the semi-manufactured part at a temperature equal to or higher than 1000°C and or sufficient to austenitize at least 80%, preferably at least 90%, more preferably at least 99% of the steel of said tracked vehicle part;5.3) cooling the forged semimanufactured part in air;5.4) obtaining the finished retaining collar 382 or another part of a tracked vehicle or of an undercarriage assembly of a tracked vehicle from the cooled semimanufactured part.

[0056] Advantageously after step S.3) the cooled semimanufactured part is machined -for example milled, bored, turned, grinded or broached- without being treated with quenching and tempering in or however through a heat treatment liquid before being machined.

[0057] In a third aspect the present invention relates to a part of a tracked vehicle obtained through the previously described process.

[0058] The compositions of the steel previously described allow the retaining collar 382 or another part of a tracked vehicle to undergo heat treatments lacking quenching or tempering through cooling liquids, for example through immersion in liquid baths; on thecontrary the mechanical parts having the previously described composition can be success fully cooled in air after forging or other hot forming operations , saving time and reducing costs and reducing environmental pollution, since there are no heat treating liquids to be disposed .

[0059] The steel of the finished retaining collar 382 or another part of a tracked vehicle so obtained has a finer grain and hence the same or better mechanical features , such as mechanical resistance and hardness , than those of steel hardened and tempered with heat treatment liquids .

[0060] The undercarriage assembly 3 can comprise one or more idle wheel shafts 385 , each of which extending through a respective idle wheel 36 so as to allow the latter to rotate about itsel f and the idler wheel shaft 385 .

[0061] Each idle wheel shaft 385 can be fixed at one of its ends to the rest of the undercarriage assembly 3.

[0062] Each idle wheel 36 can be axially blocked to its respective idle wheel shafts 385 by means of an idle wheel retaining collar 387 .

[0063] The collar 387 can be axially fixed to the idle wheel shafts 385 by means of a circlip 386 ( Figure 3 ) or a retaining pin .

[0064] The collar 387 has preferably a substantially annular shape , has preferably a diameter comprised between 40-200 millimetres , or between 50-150 millimetres or between 80-100 millimetres and / or an average or maximum thickness , measured in an axialdirection, preferably comprised between 20-100 millimetres or between 25-75 millimetres or 40-50 millimetres .

[0065] The retaining collars 382, 387 or other parts of an undercarriage can be obtained from the following process .

[0066] A semimanufactured product is obtained for example through forging.

[0067] Just after being forged, machined or however shaped the semimanufactured product can have a temperature preferably comprised between 1150-1250 °C, between 1180- 1230 °C, or however a temperature sufficient for austenitizing at least 80%, preferably at least 90%, more preferably at least 99% of the steel of said semimanufactured product (Step 1) .

[0068] Preferably the semimanufactured products are then cooled down in air or other cooling gases to about 550- 650°C or about 600°C (Step 2) .

[0069] The cooling of step 2) is preferably carried out in ambient air, preferably at a rate of about 25-35°C per minute; it can be carried out through natural or forced thermal convection.

[0070] Preferably the semimanufactured products are subsequently cooled down in air or other cooling gases to about ambient temperature, for example at about 25°C or 20°C (Step 3) .

[0071] The cooling of step 2) is preferably carried out through natural thermal convection.

[0072] This process forms f erric / pearlitic fine-grained structures in the steel, in the absence of bainite andmartensite, allowing to achieve the above mentioned hardness and strength values.

[0073] Advantageously the retaining collars 382, 387 or other parts of an undercarriage can undergo no further heat treatments, in particular heat treatments carried out with cooling liquids, for example by immersing such undercarriage parts in baths of a suitable cooling liquid .

[0074] The embodiments previously described can be modified in several ways without departing from the scope of the present invention.

[0075] For example, as previously explained, the present invention is not restricted to the retaining collar 382 but it relates also to other parts of a tracked vehicle, for example the idle wheels 36, the driving wheel 34, the side subassemblies 30A, 30B of the undercarriage of a tracked vehicle, pins, shafts or other parts of the crawler track 32, track shoes, the roller body 380, the roller shaft 381, the idle wheel retaining collar 387, the idle wheel shafts 385 or other shafts having for example an overall length comprised between 100-350 millimetres and / or a maximum or average diameter comprised between 10-100 millimetres or 20-60 millimetres; single metal plates, shells or other assemblies comprising one or more metal plates -for example welded together- wherein such plates can have an average or maximum thickness for example comprised between 2-30 millimetres or 3-20 millimetres, 4-15 millimetres, 5-10 millimetres, rollers, toothed wheelsor other wheels, rings or bushings having for example one or more of the following dimensions:-an axial length comprised between 50-400 millimetres or100-350 millimetres ;-a maximum or average diameter comprised between 5-100 millimetres or 20-60 millimetres;-a maximum or average thickness comprised between 10-500 millimetres, 20-400 millimetres or 30-350 millimetres.

[0076] A tracked vehicle according to the present invention can be not only a compact track loader 1 but also another kind of vehicle such as a bulldozer, excavator, grader, mobile drill, tractor, crawler, tank, heavy equipment vehicle, a earthmoving machine, a vehicle to be used for example in mining, heavy constructions, demolition and waste disposal.

[0077] Instead of or in addition to a blade 9 such tracked vehicle can be provided with other kinds of tools, such as a bucket, ripper, auger, pile driver, shears, hydraulic hammer.

[0078] Any reference in this specification to "One embodiment ," "an embodiment ", "example embodiment, "etc, means that a particular feature, structure, or feature described in connection with the embodiment is included in at least one embodiment of the invention.

[0079] The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment.

[0080] Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purviewof one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

[0081] All constructional details can be replaced with technically equivalent elements.

[0082] A wording such as "A comprises B, C, D" or "A is made up of B, C, D" is to be understood as encompassing and disclosing the particular case of "A consists of B, C, D".

[0083] Wordings such as "A comprises an element B" when not differently specified is to be understood as "A comprises one or more elements B" .

[0084] Mentions of a "first, second, third... n-th entity" merely intend to distinguishing the entities one from another but the mention of a n-th entity does not necessarily imply the existence of a first, second, third ... (n-l)-th entity.

[0085] Examples and lists of possible alternatives are to be understood as non-exhaustive .

Claims

CLAIMS1) Part of a tracked vehicle (1) , for example of an undercarriage assembly (30A, 30B) of a tracked vehicle made of a steel having one or more of the following features :-a content of carbon comprised between 0,1-0, 7 %wt;-a content of manganese comprised between 0,6-2 % wt;-a content of silicon equal to or lower than 1,3 % wt -a content of chromium equal to or lower than 0,8 % wt -a content of sulfur equal to or lower than 0,1 % wt -a content of phosphorus equal to or lower than 0,05 % wt ;-a content of molybdenum equal to or lower than 0,13 % wt-a content of nitrogen equal to or lower than 0,04 % wt -a content of niobium equal to or lower than 0,07 % wt -a content of vanadium equal to or lower than 0,4 % wt; -wherein said contents are the weight percent of the corresponding substance.2) Part of a tracked vehicle (1) according to claim 1, made of a steel having one or more of the following features :-a content of carbon comprised between 0,15-0,5 %wt;-a content of manganese comprised between 1-2 % wt;-a content of silicon comprised between 0,05-1 % wt-a content of chromium equal to or lower than 0,6 % wt -a content of sulfur comprised between 0,01-0,08 % wt-a content of phosphorus equal to or lower than 0,04 % wt-a content of molybdenum equal to or lower than 0,1 % wt -a content of nitrogen equal to or lower than 0,03 % wt-a content of vanadium equal to or lower than 0,3 % wt; -a content of titanium equal to or lower than 0,001% wt or 0, 006 % wt .3) Part of a tracked vehicle (1) according to claim 1 or 2, made of a steel having one or more of the following features :-a content of carbon comprised between 0,4-0, 5 %wt;-a content of manganese comprised between 1-1,8 % wt;-a content of silicon comprised between 0,1-0, 9 % wt-a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,015-0,07 % wt -a content of phosphorus equal to or lower than 0,035 % wt-a content of molybdenum equal to or lower than 0,09 % wt-a content of nitrogen comprised between 0,005-0,03 % wt -a content of vanadium comprised between 0,05-0,3 % wt .4) Part of a tracked vehicle (1) according to one or more preceding claims, made of a steel having one or more of the following features:-a content of carbon comprised between 0,42-0,49 %wt;-a content of manganese comprised between 1,2-1, 6 % wt;-a content of silicon comprised between 0,15-0,8 % wt-a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,02-0,06 % wt -a content of phosphorus equal to or lower than 0,025 % wt-a content of molybdenum equal to or lower than 0,08 % wt-a content of nitrogen comprised between 0,01-0,02 % wt-a content of vanadium comprised between 0,08-0,2 % wt .5) Part of a tracked vehicle (1) according to one or more preceding claims, made of a steel having one or more of the following features:-a content of carbon comprised between 0,43-0,47 %wt; -a content of manganese comprised between 1,3-1, 5 % wt; -a content of silicon comprised between 0,3-0, 6 % wt -a content of chromium equal to or lower than 0,2 % wt; -a content of sulfur comprised between 0,03-0,05 % wt -a content of phosphorus equal to or lower than 0,015 % wt ;-a content of molybdenum equal to or lower than 0,06 % wt-a content of nitrogen comprised between 0,01-0,016 % wt -a content of vanadium comprised between 0,1-0,17 % wt .6) Part of a tracked vehicle (1) according to one or more preceding claims, wherein said part is chosen from the following set of parts of an undercarriage assembly of said tracked vehicle (1) : a retaining collar (382) for example for a compact track loader roller assembly (38) , a retaining collar (387) for rotatably fixing an idle wheel (36) for example of a compact track loader roller assembly (38) , an annular collar having a diameter comprised between 35-200 millimetres and / or an average of maximum thickness comprised between 15-100 millimetres, an idle whee 1 (36) configured for rolling over or under a continuous crawler track of said undercarriage, a driving wheel (34) configured forengaging with, rolling over or under or driving a continuous crawler track of said undercarriage, a side subassemblies (30A, 30B) , a pin, a shaft or other parts of the crawler track (32) of said undercarriage assembly, a track shoe, a roller body (380) , a roller shaft (381) , an idle wheel retaining collar (387) , an idle wheel shafts (385) , a shafts having an overall length comprised between 100-350 millimetres and / or a maximum or average diameter comprised between 10-100 millimetres, a metal plate or shell having an average or maximum thickness for example comprised between 2-30 millimetres, a roller, a toothed wheel, a wheel, a ring, a bushing wherein said parts have one or more of the following dimensions : -an axial length comprised between 50-400 millimetres; -a maximum or average diameter comprised between 5-100 millimetres ;-a maximum or average thickness comprised between 10-500 millimetres .7) Part of a tracked vehicle (1) according to one or more preceding claims, wherein said part is obtained through a manufacturing process comprising the following steps :5.7.1) obtaining a semi-manufactured part by forging or machining;5.7.2) bringing or maintaining the semi-manufactured part at a temperature equal to or higher than 1000°C and or sufficient to austenitize at least 80% of the steel of said tracked vehicle part;S.7.3) cooling the semimanufactured part in air; -obtaining the final undercarriage part from the cooled semimanufactured part.8) Part of a tracked vehicle (1) according to one or more previous claims, having one or more of the following features :-a grain equal to or greater than 5, according to ASTM norms ;-a final hardness comprised between 250-400 HB (Brinell Hardness ) ;-a tensile strength at rupture (RM) comprised between 800-1400 MPa;-a 0.2% offset yield strength (RP0.2) comprised between 450-750 MPa.9) Undercarriage assembly of a tracked vehicle (1) , comprising a part having the features according to one or more preceding claims.10) Undercarriage assembly according to claim 9, comprising one of more of the following parts or assemblies: a continuous crawler track (32) , an undercarriage frame (33) , a driving wheel (34) , one or more idle wheels (36) and a plurality of roller ass e mb lies (38) .11) Tracked vehicle (1) comprising a part (32, 34, 36,38, 380, 381, 382, 385, 387, 30A, 30B) having the features according to one or more claims 1-8.12) Tracked vehicle (1) according to claim 11, whereinthe tracked vehicle is chosen from the following set: a bulldozer, excavator, grader, mobile drill, tractor, crawler, tank, heavy equipment vehicle, a earthmoving machine, a vehicle to be used for example in mining, heavy constructions, demolition and waste disposal.13) Process for producing a part of a tracked vehicle, for example a part of an undercarriage assembly of a tracked vehicle, comprising the following steps:5.13.1) obtaining a semi-manufactured part through forging or machining, wherein said semi-manufactured part is made of a steel having the features according to one or more claims 1-5;5.13.2) bringing or maintaining the semi-manufactured part at a temperature equal to or higher than 1000°C and / or sufficient to austenitize at least 80% of the steel of said tracked vehicle part5.13.3) cooling the semimanufactured part in air;5.13.4) obtaining the final undercarriage part from the cooled semimanufactured part.14) Process according to claim 13, wherein after step S.13.2) the cooled forged semimanufactured part is machined without being treated with quenching and tempering in a heat treatment liquid before being machined .15) Process according to claim 13 or 14, wherein in step S.13.2) the semi-manufactured part is brought or maintained at a temperature comprised between 1180- 1230°C.16) Process according to one or more claims 13-15, wherein in step S.13.3) the semimanufactured part is cooled down to a temperature equal to or lower than 900°C.17) Process according to one or more claims 13-16, wherein in step S.13.3) the semimanufactured part is cooled down to a temperature comprised between 600-700°C through forced thermal convection.18) Process according to one or more claims 13-16, wherein in step S.13.3) the semimanufactured part is cooled down to a temperature comprised between -20°C and 40°C and eventually equal to or lower than 25°C, and said cooling between 600°C and 40°C is carried out through natural thermal convection.

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