Method of fabricating work holders of tube mills at lengthwise tube rolling

FIELD: tube rolling.

SUBSTANCE: method includes casting of blanks out of alloy with contents of carbon 1.8-3.2% and chromium 30.0-35.0%, thermal aging, machining of surface of the blank to rough and finishing dimensions with a cutting tool, combining machining with heating of a machined portion; at that the surface of the machined potion is heated up to 600-800° C at a length of 3.0-3.5 mm with a plasma arc of current 60-160 A and power 12 kilowatt; the center of the heated portion is located in front of the cutting tool edge at a distance of not more, than 20 mm.

EFFECT: reduction of labour input at machining, upgraded accuracy of both geometric dimensions of a finished product and of micro hardness of the surface layer, and increased wear resistance of work holders not less, than two times.

1 dwg

 

The invention relates to pipe manufacture and can be used in the manufacture of the mandrel mills longitudinal rolling of pipes.

A known method of manufacturing bars of steel grade HN with the following content elements: carbon 1,2-1,7%, chromium of 14.0-17.5 per cent, Nickel, 0.7 to 1.1%, manganese 0.2 to 0.7%, silicon 0.2 to 0.7 percent, and including the casting of billets, machined on a lathe and oxidative annealing with the hardness of the finished mandrel 20-44 HRC [TI path In-1-74 "Production primary production tool" Section 13 "automatic Mandrel mills", 1974, p.27-32].

The disadvantage of this method is the low resistance of the mandrel equal to 30-50 passages that are caused by insufficient content of chromium carbides Cr7With3in the working surface layer due to chemical composition and mechanical turning, which leads to the accumulation of metal pipe on the mandrel and education grid crack height.

The closest in technical essence and dostigaemye the results of the present invention is a method of manufacturing a mandrel mills longitudinal rolling of tubes of cast iron brand SL with the following content elements: carbon 2,7-3,2%, chromium 30,0-35,0%, silicon up to 1.25%manganese, 0.3 to 0.6%, Nickel 2,5-3,0%, vanadium of 0.2-0.3%, which includes the casting mandrel "in size with hardness 4-52 HRC and use them in melted form, without heat treatment [Beloshapko MV, Danicek YEAR, Nosko B.C., Shevtsova E.V. "Ways of increasing the resistance of the mandrel mills longitudinal rolling in the manufacture of tubes made of carbon, stainless and alloy steels"/ collection: all-Union scientific-technical conference process Improvement longitudinal rolling of pipes" (theses of reports). - Chelyabinsk /UralNITI/, 1980, p.116-118].

The disadvantage of the prototype is the low accuracy of the geometric dimensions of the mandrel, which is a consequence of the mode of production, which affects the accuracy of manufacturing of pipes.

An object of the invention is to reduce the complexity of mechanical processing, providing high accuracy of geometric dimensions of the finished product and to increase the resistance of the mandrel due to the increase of microhardness of the surface layer.

The solution of the technical problem is achieved in that in the method of manufacturing a mandrel mills longitudinal rolling of pipes, including the casting of billets of alloy content, wt.%: carbon 1.8 to 3.2% and chromium 30,0-35,0%, the workpiece is subjected to heat aging, and then carry out the machining surface of the workpiece by cutting on rough and finish dimensions using the cutting tool, combining with the heat treated area, thus heating the surface of this area lead to 600-800°With a depth of 3.0-3.5 mm plasma dugo which with amperage 60-160 And, power up to 12 kW and with the location of the center of the spot heating front edge of the cutting tool at a distance of not more than 20 mm.

A method of manufacturing a mandrel mills longitudinal rolling of pipes is carried out as follows.

Metal casting is made or in electric arc furnace or induction furnace. The composition of the charge loaded into the furnace, is calculated for the desired chemical composition taking into account the degree of absorption and intoxication. The casting mandrel is made in sand moulds in raw.

After casting produce knockout forms on vylivnoi lattice with subsequent cleaning of the workpieces in the tumbling drum and cutting feeders on the rough-grinding machine.

Thermal ageing preparations to relieve casting stresses is carried out in an electric furnace at a temperature of 680°aged at least 6 hours.

The essence of the process of mechanical machining of the workpiece mandrel by heating the treated surface by the plasma arc is illustrated in the drawing, which shows a working area CNC lathe installed and secured by the workpiece.

The workpiece 1 is placed in the working area of the lathe and is fixed with the aid of the mandrel 2 and 3. The plasma torch 4, located on the support plate of the machine so that the distance L (mm) from the center of heating spot to the edge of the cutter 5 was not more than 20 mm, the move is seen when processing together with the cutter, heating the plasma arc only the area to be cutting. The plasma torch 4 by using the caliper is applied to the workpiece 1 from the large end and mounted at its ends on the cylindrical surface at a distance of 8-12 mm from the edge of the nozzle of the plasma torch to the workpiece surface. Before ignition of the arc in the plasma torch is supplied cooling water, plasma and shield gas. After turning on the power supply turns on duty arc, the normal combustion mode which is characterized by continuous torch, coaxially to the axis of the plasma channel of the nozzle. Further included the main movement of the workpiece V (m/min), and a main arc current which is equal 60-160 A, and a maximum capacity of 12 kW. The heating temperature plasma arc, upon reaching which there is a decrease in strength and increase the ductility of the workpiece material, 600-800°C. After the initiation of the main arc enables the movement of the caliper S (mm/Rev) together with the plasma torch and chisel.

Machining of the workpiece, the mandrel is carried out by first cutting to rough size (one pass), in which the thickness t (mm) cutting metal layer is not more than 3 mm, followed by cutting to finishing size (one pass), in which the thickness of the cutting layer is not more than 1 mm, the heat content of the deposited plasma arc penetrates the mass of the workpiece on a small chap is inu, focusing primarily within the cutting layer and drifted down the chips already in the first turnover of the workpiece, and the remaining heat is rapidly removed during subsequent revolutions. The use of plasma heating during cutting, on the one hand, lowers the mechanical properties of the processed material and facilitates the cutting process, and on the other, in the surface layer of plastic deformation occurs at a depth of 110 μm, characterized by the increase of microhardness at 70-85%.

Oxidative annealing of the workpiece, the mandrel is held in the same furnaces, and thermal aging at a temperature of 1050°aged not less than 1 h Holding annealing required for applying to the treated surface of the mandrel oxide film, prevents the accumulation of metal pipe on the mandrel during rolling and not lead to any structural or phase transformations in metal.

Conducted by the applicant's analysis of the prior art, including searching by the patent and scientific and technical information sources, and identify sources that contain information about the equivalents of the claimed invention, has allowed to establish that the applicant had not found the source, which is characterized by symptoms that are identical to all the essential features of the claimed invention. The definition from the list of identified unique prototype, as the most similar sosaku the particular features analog, helped to establish the essential attitude, perceived by the applicant to the technical result of the distinctive features in the proposed method, set forth in the claims.

Therefore, the claimed invention meets the condition of "novelty."

The study of other known technical solutions in this field of technology features that distinguish the claimed solution to the prototype, have not been identified. Therefore, the claimed invention meets the condition of "inventive step".

The method was tested and implemented on OAO "Sinarsky pipe plant".

Was cast 40 blanks pots made of cast iron brand SF content, wt.%: carbon of 2.5-3.0% and chromium 30,0-35,0%, and 40 billets bars of steel grade HN (bidule) content, wt.%: carbon 1.8 to 2.1% and chromium 30,0-35,0%, the finishing size of the cylindrical band which must be equal to 106 mm After removal of the sprue, clean from the sand in the tumbling drum held thermal ageing of material in an electric furnace at a temperature of 680°aged for 6 hours.

Machining of blanks pots were performed on a lathe on the proposed technology.

After machining was conducted oxidative annealing in an electric furnace at a temperature of 1050°aged not less than 1 h of the Mandrel is donkey oxidative annealing have around the treated surface oxide layer of bluish-gray color.

The proposed method of manufacturing a mandrel mills longitudinal rolling of tubes of cast iron, and steel reduces the complexity of machining 1.5 times, high dimensional accuracy of the finished product and the increase in the microhardness of the surface layer due to exposure to a plasma arc, which leads to an increase in the resistance of the mandrel not less than 2 times.

A method of manufacturing a mandrel mills longitudinal rolling of pipes, including casting billets of metal content, wt.%: carbon 1.8 to 3.2 and chromium 30,0-35,0, characterized in that the workpiece is subjected to heat aging, and then carry out the machining surface of the workpiece by cutting on rough and finish dimensions using the cutting tool, combining with the heat treated area, thus heating the surface of this area lead to 600-800°With a depth of 3.0-3.5 mm plasma arc amperage 60-160 And power up to 12 kW and with the location of the center of the spot heating front edge of the cutting tool at a distance of not more than 20 mm.



 

Same patents:

FIELD: metallurgy.

SUBSTANCE: for decreasing the relevant amount of blowhole in clax, created on the pipe surface, and exceeding of resistance to atmosphere corrosion, the pipe is made of steel containing the following mass in %: С (0.15-0.22), Si (0.1-1.0), Mn (0.3-1.0), Cr (12.0-16.0) and it (pipe) has the relevant amount of blowhole in compliance with the thickness of clax from the sideview of the steel pipe, which satisfy the following correlation: ≤-6.69 х ln (ds) + 40.83, where: ds - thickness of the clax (mcm), ln - natural logarithm. The method of producing the pipe includes the pipe heating during 5-30 min up to the temperature (Ас3 + 20)°С - 980°С in atmosphere containing oxygen in total amount 2.5 volume.% or less and water vapor in amount of 15.0 volume % or less, the tempering of heated pipe with cooling speed 1-40°С/sec from 980°С up to the point А with cooling speed less then 1°С/sec, from point А till point В and with the cooling speed 5-40°С/sec from point В up to the temperature of environment, where point A lies in the interval 680-350°С and point В - 300-150°С, dispersion of the water under high pressure 490 N/mm2 or higher to the side surface of the still pipe during that part of cooling from temperature of 900°С up to the point А of mentioned tempering.

EFFECT: reduction of the blowholes amount in the clax.

16 cl, 6 tbl, 10 dwg, 1 ex

FIELD: mechanical engineering; methods of volumetric hardenings of the metallic products.

SUBSTANCE: the invention is pertaining to the field of volumetric hardenings of the metallic products by methods of training mechanical actions. The technical result of the invention is the increased cyclic service life. For reaching the technical result the cylindrical thin-walled pipe is subjected to the multiple training action at the continuous gyration of the main axes of the stressed state by the simultaneous application of the stretching axial force, the interior pressure and the twisting moment. At that the axial thrust and the interior pressure are applied in the form of the constant sign cycles in the opposite phase, and the torque - in compliance with the symmetrical cycle with the lag or with the phase advance by the quarter of the cycle concerning the phase of one of the extreme values of the axial thrust. At that the formed rotational training biaxial stretching is given the helical rising character with bringing the maximal main stress up to the level of the material tensile strength at the rotation frequency of the main axes of the stress state of no less than 5-10 Hz.

EFFECT: the invention ensures the increased cyclic service life of the of the metallic thin-wall cylindrical pipes.

6 dwg

FIELD: processes and equipment for heat treatment of hollow products such as tubes operating in aggressive media of oil sites.

SUBSTANCE: method comprises steps of heating tube by passing through it high-density electric current; cooling tube surfaces by means of cooling agent while using electric current with density up to 15 A/ mm2 and heating up to temperature not exceeding Ac1. Then soaking is realized at such temperature for time period no more than 20 min and cooling is performed at rate 75 - 100°C/s. In order to create normalized residual compression stresses on outer surface of tube its inner surface is cooled. In order to create normalized residual stresses on inner surface of tube the last is cooled at side of its outer surface. Heat treatment modes allow achieve desired temperature drops and respective plastic deformations in micro-regions along thickness of tube walls.

EFFECT: improved quality of tubes due to their enhanced corrosion resistance and mechanical parameters.

3 cl, 1 dwg, 1 ex

FIELD: rolled tube production, namely processes for making conversion tube blank for rolling cold-rolled large and mean diameter tubes from titanium base alloys with improved accuracy of their wall geometry, possibly in lengthwise welding mills and in other mills with use of conversion tube blank.

SUBSTANCE: method comprises steps of planing sheet along its width; preparing edges of sheet blank to welding; shaping sheet blank in rollers for producing tube conversion blank for rolling large diameter tube; welding lengthwise edges of blank on moving copper shoe in argon gas shield atmosphere by means of consumable electrode of the same kind of alloy at reinforcing outer and inner seams. Sheet blank edges to be welded are in the form of blunted broken line. Geometry size of said broken line are determined according to expressions: A= S/3; C = (0.35 - 0.45)S; D = (B - C)/2; D' =(B'- C)/2; K = K' = A = S/3 where S - wall thickness of sheet blank, mm; A - blunting value of welded edges, mm; C - gap value between welded edges of sheet blank, mm; D - width of edge dressing for welding outer seam, mm; D' - width of edge dressing for welding inner seam, mm; K = K' = A - thickness value of edge dressing of outer and inner seams, mm. Welding process is realized on copper shoe at accuracy of assembling edges ± 0,5 mm. Roots of inner seams are fused by means of non-consumable electrode in argon gas shield atmosphere. Geometry size of welded seams are determined according to expressions: B = 30 - 35 mm; B' = 25 - 30 mm; H = (0.1 - 0.2)8; H' = (0.05 - 0.1)S where B - width of outer seam of conversion tube blank, mm; B' - width of inner seam of conversion tube blank, mm; H - reinforcement of outer seam of conversion tube blank, mm; H' - reinforcement of inner seam of conversion tube blank, mm. Invention allows produce high quality tubes according to ASTM B 862 -02 from welded conversion tube blanks.

EFFECT: lowered labor consumption of production of high quality tubes from conversion welded tube blanks, reduced factor of alloy consumption of conversion of straight-seam conversion tube blank to cold rolled tube, lowered cost of cold rolled tubes of titanium alloy base.

4 cl, 1 dwg, 1 tbl

FIELD: tube production, namely manufacture of welded straight-seam large-diameter tubes, possibly production of tubes of given size subjected to expanding of welded seam till level of base metal and to thermal and mechanical working.

SUBSTANCE: method comprises steps of planing sheet along width, preparing edges of sheet for welding, shaping, welding tube blanks under flux layer by one or two lengthwise seams at reinforcing outer and inner seams; heating welded seam till predetermined temperature; hot deformation till complete flattening of welded seam and thermal and mechanical working of seam. Welded seam is expanded at widening along tube perimeter. Widening of tube perimeter with one lengthwise seam is determined at sufficient accuracy according to expression ▵ = aB/S and for tubes with two lengthwise seams according to expression ▵1 = 2aB/S, where a - averaged summed width of outer and inner seams, mm; B - averaged summed height of reinforcement of outer and inner seams, mm; S-nominal thickness of tube walls, mm. Width of sheet for shaping tube blanks with one lengthwise seam is decreased by value ▵; width of sheet for shaping tube blanks with two lengthwise seams is decreased by value ▵1.

EFFECT: enhanced operational reliability of pipelines, improved quality of polyethylene cohesion for tubes with corrosion protection coating of tubes without reinforced seams, lowered consumption factor of metal.

2 cl, 1 tbl

FIELD: thermal processing, in particular, thermal reinforcement of pipes by heating of individual pipes in thermal department lines or for thermomechanical processing of pipes using rolling process heat.

SUBSTANCE: pipe cooling apparatus has casing having one side made in the form of central gear of differential planetary transmission gear with carrier formed as flange positioned on pipe with receiving funnel. Pipe has through openings positioned opposite to nozzles. Collectors are axially attached to toothed gears-satellites. Brush device is positioned for rotation within each of said collectors, said brush device being fixed on pin, whose free end portion is positioned for movement without rotation in slot provided on central gear, concentrically to main axis of transmission gear. Brush device is made spiral. Free end portion of its pin is connected to ratchet mechanism. Opening is provided in lower part of collector, with area of said opening exceeding by 3-5 times area of nozzle opening.

EFFECT: increased efficiency in controlled cooling of articles, and improved quality of articles by uniform cooling thereof.

3 cl, 5 dwg, 1 tbl

Pipe cooling method // 2291905

FIELD: pipe rolling production for thermal reinforcement of pipes in thermal department lines and hot rolling mills.

SUBSTANCE: method involves providing longitudinal movement and feeding of coolant at an angle to axis of movement by means of pairs of countercurrent jets, said jets in pairs of jets flowing without intersection with respect to one other; increasing angles of feeding said jets coinciding with direction of advancement of pipe in succession from one pair of countercurrent jets to other pair of countercurrent jets in this direction; decreasing angles of feeding jets oriented in direction opposite to direction of advancement of pipe in succession, from one pair of countercurrent jets to other pair of countercurrent jets in direction of advancement of pipe. Also, during movement by each of pipe ends past pair of countercurrent jets, coolant flow rate within it is reduced by 70-90% and simultaneously coolant flow rate in countercurrent jet is increased by 60-80%.

EFFECT: increased efficiency in cooling of pipes, provision for desired combination of properties and required values of geometric parameters of pipes.

2 cl, 3 dwg, 1 tbl

FIELD: production of pipes, in particular, drill pipes with connection locks welded thereto.

SUBSTANCE: flow line has machines for friction welding of lock connections at one and other ends of pipes, station for collecting of packet and leveling position of welded connection zones before thermal processing, induction heating chamber for induction heating before normalization procedure, induction heating chamber for heating before tempering of welded connection zones at one side of pipes collected into packet, station for leveling position of welded connection zones before thermal processing, similar induction heating chambers for normalization, cooling, induction heating before tempering of welded connection zones at other side of pipes collected into packet, water laminar cooling systems arranged at stations for leveling position of welded connection zones, and sprayers positioned in cooling chambers and adapted for water-air cooling of welded connection zones. All of mentioned parts of flow line are arranged in succession and connected with one another through transportation means. Intensified adjustable cooling sprayers are located within heating chambers for heating before normalization procedure. Welded connection zone cooling sprayer is positioned downstream of first machine for welding of lock connections.

EFFECT: increased efficiency and enhanced reliability in operation.

3 cl, 1 dwg, 1 tbl

FIELD: plastic metal working, namely manufacture of thin-wall cylindrical articles.

SUBSTANCE: apparatus includes stripper and calibration mandrel mounted in base. Upper surface of base turned to stripper has flat portion with layer of talc and three wedge cross section sectors with the same height of their wedges and with apex angle of each wedge no more than ˜1°. Stripper is in the form of nut whose face turned to base includes three wedge cross section sectors with the same height of wedges and with apex angle of each wedge no more than ˜ 1°. Height of wedges of base is equal to height of wedges of stripper. Calibration mandrel also includes preset-thickness layer of talc.

EFFECT: enlarged manufacturing possibilities, enhanced efficiency of process and high quality of articles.

3 dwg

FIELD: technology of manufacture of bellows; devices for thermal shaping of geometric sizes and form of bellows.

SUBSTANCE: proposed device is used for thermal shaping of bellows due to difference in linear expansion of mandrel and bellows; device is provided with split rings fitted between covers engageable with them and tightened by strainer. End surfaces of upper and lower rings rest against each other; they have shape-forming external cylindrical surfaces with bore for internal corrugation of bellows and bevels on internal surface of upper ring and part of external surface of lower ring resting against bevels of supporting ring. Bevels are made in form of taper surfaces. External bevel of supporting ring is made at angle relative to axis of device which is lesser than or equal to limiting friction angle of materials of upper ring and supporting ring; internal bevel of supporting ring is made at angle relative to axis of device which is larger than limiting friction angle of materials of lower ring and supporting ring. Device may include several alternating supporting rings, upper and lower rings for simultaneous thermal shaping of several bellows in strut.

EFFECT: improved quality of single-corrugation bellows by magnitude of diameters; enhanced centering and axial alignments.

13 cl, 2 dwg

FIELD: metallurgy, possibly improvement of properties of gray iron castings.

SUBSTANCE: method providing decreased volume content of graphite, disintegration of graphite inclusions and their uniform distribution along cross section of castings comprises steps of heating and cooling in each cycle while heating in each cycle is realized till 700 - 750°C and then casting is cooled in water. Number of cycles is equal to 2 - 4.

EFFECT: possibility for providing decreased volume content of disintegrated and uniformly distributed graphite in cross sections of castings.

1 ex, 1 tbl

FIELD: metallurgy, possibly improvement of properties of gray iron castings.

SUBSTANCE: method providing decreased volume content of graphite, disintegration of graphite impurities and their uniform distribution along cross section of castings comprises steps of heating and cooling gray cast iron in each cycle while cast iron is heated in each cycle till 980 - 1020°C and further it is cooled in water. Number of cycles is equal to 2 - 4.

EFFECT: decreased volume content of graphite, disintegration of graphite inclusions and their uniform distribution along cross section of castings.

1 tbl, 1 ex

FIELD: processes for heat treatment of cast iron parts with spheroidal graphite.

SUBSTANCE: method comprises steps of testing initial structure by means of coercive force meter and selecting heat treatment modes on base of testing results. Parts are subjected to austenization at 880 - 930°C; interim cooling of parts in furnace till temperature in range Ar3 - Ar1 ; cooling at rate 5 -10°C per minute till temperature in range between temperature of starting A - P conversion and temperature exceeding by 50°C maximum-stability of temperature of austenite being converted to upper bainite or troostite. Then part is subjected to isothermal soaking at such temperature till maximally possible degree of A - P conversion. After cooling structure is inspected by means of coercive force meter for detecting tendency of pearlite and tempered bainite to changes at further nitriding. Depending upon inspection results tempering mode is selected and after such tempering final testing of structure by means of coercive force meter is realized according to index values of scale developed on base of investigating relationship of readings of coercive force meter from initial structure and its changes at nitriding process and also from growth and warping of parts at nitriding.

EFFECT: possibility for producing stable structure resistant against changes at nitriding process.

2 cl, 1 ex

FIELD: ferrous metallurgy, namely production of high-strength cast irons with spheroidal graphite, possibly production of cast products having high strength, ductility and impact viscosity.

SUBSTANCE: cast iron contains, mass%: carbon, 3.28 - 4.03; silicon, 2.34 - 3.62; manganese, 0.22 - 0.53; copper, 1.16 - 2.34; molybdenum, 0.21 - 0.52; magnesium, 0.02 - 0.05; barium, 0.03 - 0.08; rare-earth metal, 0.02 - 0.06; iron and inevitable impurities, the balance. Cast pieces of such cast iron are subjected to heat treatment comprising stepped austenization at heating up to 820 - 830°C; soaking for 0.5 h and further heating till 870 - 900°C and soaking for 0.5 - 1.5 h. Then castings are cooled till temperature less than 500°C. Cooling rate is controlled depending upon wall thickness of cast piece. If wall thickness is less than 20 mm, cast product is cooled in air; if wall thickness is 25 -40 mm cast product is cooled in water for 4 - 5 s; if wall thickness exceeds 40 mm cast product is cooled in water for 6 - 10 s. Then casting are subjected to thermocycling in temperature range 270 - 390°C for 1.5 -3 h and to air cooling.

EFFECT: improved stable mechanical properties of castings with different wall thickness.

2 cl, 2 dwg

FIELD: metallurgy; deformation thermal treatment of iron-carbon alloys; manufacture of hot-deformed seamless tubes.

SUBSTANCE: proposed method includes preliminary heat treatment of high-strength cast-iron billet at temperature Ac3+200°C continued for 10 h and followed by heating the billet at deformation temperature, deformation of billet and heat treatment of tube.

EFFECT: improved quality of tubes; extended field of application of this method.

4 cl, 2 ex

FIELD: metallurgy; production of ingots made out of mottled cast iron with austenitic-bainite structure.

SUBSTANCE: the invention is dealt with metallurgy, in particular, with development of a method of production of mottled cast irons with globular graphite, which may be used for manufacture of components being worn under action of increased loadings. The method provides, that the mottled cast iron is melted down in the induction furnace, the liquid melt at pouring into a ladle is modified with magnesium-bearing addition alloys for formation of the ball-shaped graphite impurities in the ingots and during casting into a sandy-argillaceous mold expos it to inoculating modification. The ingots after crystallization are pulled out from the molds at the temperature of 900-1000°C, transposed to a furnace with temperature of 950-1000°C and keep there during 10-30 mines. After the aging the ingot is exposed to quenching in an isothermal bath at the temperature of 300-320°C within 1-1.5 hour. At that they use the cast iron of following chemical composition, (in mass %): carbon - 3.2-3.4, silicon - 3.0-3.3, manganese - 0.3-0.4, magnesium - 0.04-0.07, molybdenum - 1.5-1.7, nickel - 2.2-2.6, sulfur - 0.01-0.012, phosphorus - 0.06-0.08, iron - the rest. The invention allows to obtain a mottled cast iron with globular graphite and austenitic-bainite structure, high impact resistance, strength, hardness, wear resistance and quasi-isotropy.

EFFECT: the invention ensures production of a mottled cast iron with globular graphite and austenitic-bainite structure resistant to wear under action of increased loadings.

1 ex

The invention relates to metallurgy, in particular to thermal processing of large workpieces made of pearlitic gray cast iron, and can be used in the production of cylinder sleeves powerful marine diesel engines

The invention relates to metallurgy, in particular to methods of producing cast iron with compact forms of graphite, i.e
The invention relates to electro-contact processing and can be used in machine building and repair of machines for hardening the inner surface of the cast-iron parts, which are the body of rotation

FIELD: production of rolled tubes, possibly manufacture and operation of drifts of pilger mills.

SUBSTANCE: method comprises steps of casting ingots of carbon steels; applying onto ingot surface by surfacing heat- and wear- resistant layer; making from ingots drift blanks by pilger rolling; performing heat treatment of drift blanks; then performing mechanical working of blank to final size for further strengthening of it due to rolling around by means of roller. During operation of drifts after occurring of net of burnout cracking drifts are subjected to multiple returning till removing heat- and wear-resistant layer. Then new heat and wear resistant layer is applied by surfacing, heat treatment and mechanical working till final size are realized for further strengthening of blank due to rolling around by roller. Heat and wear resistant layer is applied beginning from bottom end of ingot along 2/3 of its height. After returning of drifts heat and wear resistant layer is applied along 2/3 of their length beginning from drift head with further smooth transition along length 100 - 150 mm. Thickness values of heat and wear resistant layer on ingots and on drift blanks are determined according to given expressions.

EFFECT: improved strength of drifts, rational metal consumption.

2 cl, 1 tbl

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