Round merchant shape made from medium-carbon chromium-containing steel

FIELD: metallurgy; production of merchant shapes for manufacture of spherical pins, end-pieces of rods and spherical supports for automobile suspensions.

SUBSTANCE: merchant shapes are molten from steel containing the following components, mass-%: carbon, 0.35-0.42; manganese, 0.50-0.80; silicon, 0.17-0.37; chromium, 0.80-1.10; sulfur, 0.020-0.040; vanadium, 0.005-0.020; calcium, 0.001-0.010; oxygen, 0.001-0.015; nickel, up to 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; nitrogen, no more than 0.015; the remainder being iron and unavoidable admixtures at oxygen-to-calcium ratio equal to 1-4.5 and calcium-to-sulfur ratio ≥0.065. Proposed merchant shapes contains nonmetallic inclusions of sulfide having double-layer structure; maximum contamination with nonmetallic inclusions pertaining to sulfides, oxides, silicates and nitrides does not exceed 3 points; it contains also structure consisting of 80% of granular pearlite; size of actual grain is 5-10 points at diameter ranging from 10 to 30 mm; provision is made for decarbonized layer not exceeding 1.5% of diameter, magnitude of cold upsetting is no less than 1/3 of height, rupture strength does not exceed 600 Mpa; relative elongation is no less than 18% and relative reduction in area is no less than 60%.

EFFECT: enhanced machinability at full hardenability of shapes up to 30 mm in diameter; retaining of technological ductility of steel.

1 ex

 

The invention relates to the field of metallurgy, in particular to the production of rolled, round, medium hromsoderzhashchej steel high machinability, used for the manufacture of ball pins, rod end bearings and ball joints suspension of the vehicle obtained by the method of cold forming processes.

Known rolled, round, steel, containing (wt.%): carbon 0,36-0,44, manganese 0.50 to 0.80, silicon 0.25 to 0.45, and chrome 0,85-1,50, titanium 0,02-0,04, alumni 0,005-0,015, boron 0,003-0,005, calcium 0,001-0,004, copper 0,2-0,7, Nickel, 0.2 to 0.5, barium 0.01 to 0.04, iron rest, when the ratio of Cu/Mn+Ni=0.15 to 0.75 in. (Patent RU 2023048 C1, With 22 38/54 from 22.06.1992, published 15.11.1994,).

The disadvantage of this steel is relatively high nitrogen content and the absence in the composition of the elements that protect the boron from binding in the nitrides, which in some cases will not allow to achieve the claimed by the authors of the effect for improving the hardenability characteristics.

Closest to the technical essence and the achieved effect of the present invention is rolled round of the medium hromsoderzhashchej steel containing (wt.%): the carbon of 0.35-0.45, and manganese from 0.50 to 0.80, silicon 0,17-0,37, chrome 0,8-1,10, vanadium 0,04-0,09, aluminum 0,005-0,015, calcium 0,001-0,004, nitrogen 0,005-0,009, copper 0,25-0,40, magnesium 0,0005-0,0009 iron and inevitable impurities rest. This soda is the sulfur content is 0.01-0.02 wt.%; the phosphorus content is 0,015-0,020 wt.% (USSR author's certificate SU 1216241 And 22 With 38/24 published 07.03.1986 year).

The technical result of the invention is to improve characteristics machinability while increasing hardenability characteristics while ensuring end-to-end hardenability rolled diameter up to 30 mm, as well as maintaining a high level of technological plasticity steel.

To achieve a technical result in long products rolling, all produced from medium carbon steel containing carbon and alloying elements that have the specified quality parameters become non-metallic inclusions, structure, mechanical properties and hardenability and machinability, the steel contains the following ratio of components, wt.%:

Carbon0,35-0,42
Manganese0,50-0,80
Silicon0,17-0,37
Chrome0,80-1,10
Sulfur0,020-0,040
Vanadiumof 0,005 0,020
Calcium0,001-0,010
Oxygen0,001-0,015
Nickelto 0.25
CopperNot more than 0,25
MolybdenumNot more than 0.10
ArsenicNot more than 0.08
NitrogenLess than 0.015
Iron and inevitable impuritiesThe rest,

when performing ratios:

oxygen/calcium= 1÷4,5; calcium/sulfur ≥0,065

The maximum score of contamination of steel, non-metallic inclusions in sulfides having a two-layer structure, oxides, silicates and nitrides of not greater than 3 points for each type of inclusions, car has a homogeneous spheroidizing structure in length, consisting of not less than 80% granular perlite, the amount of the actual grain 5-10 point, diameter from 10 to 30 mm, de-carbonized layer is not more than 1-5% of the diameter, the amount of cold upsetting of not less than 1/3 of the height, ultimate strength, not more than 600 MPa, elongation at less than 18%, the relative narrowing of at least 60%.

Given the combination of alloying elements allow you to get in the proposed steel bars hot-rolled round with a diameter up to 30 mm) favorable lamellar structure with globular sandwich inclusions, which provides, on the one hand, high characteristics of cutting even a broad incisors when the transverse axis of the cutting tool, on the other hand, a favorable combination of characteristics durable the STI and plasticity.

Carbon is introduced into the composition of this steel to provide the required level of strength and hardenability. The upper limit of the content of carbon (0.42%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively 0.35% providing the required level of strength and hardenability of the steel.

Carbonitrides element vanadium is introduced into the composition of this steel to ensure a fine, uniform grain structure, which will increase as the level of its strength, and to provide a given level of ductility. While vanadium manages the processes in the lower part of the austenitic region and microtecnica temperature range (determines the tendency to grain growth of austenite, stabilizes the structure during thermomechanical processing, increases the temperature of recrystallization and, consequently, affects the character γ-α- transformation. Vanadium also contributes to hardening of the steel during thermolysine. The upper limit of the content of vanadium 0.02% due to the need to ensure the required level of ductility of steel, and the bottom, respectively 0.005% by providing the required strength level of the steel.

Manganese and chromium are used, on the one hand, as a solid solution hardeners, on the other hand, elements substantially the increasing the stability of the supercooled austenite steel. The upper levels of manganese 0.80% chromium 1.10% determined by the need to ensure the required level of ductility of steel, and the lower - 0.50% manganese, and 0.80% chromium, respectively - the need to ensure the required level of strength and hardenability of the steel.

Silicon belongs to territooriumil elements. The lower limit for silicon 0.17% caused by the deoxidation of steel. The silicon content higher 0.37% will adversely affect the characteristics of ductility of steel.

Sulfur determines the level of ductility of steel. The upper limit (0.040%) due to the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit (0.020%) - questions-tech production, as well as to provide a specified level of machinability of the steel.

Calcium is an element, modifying nonmetallic inclusions. The upper limit (0.010%), as in the case of sulfur caused by the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit (0.001%) - questions-tech production.

Oxygen, forming an oxide film on the sulfides, helps to improve the machinability of steel cutting, while maintaining a high complex consumer properties of the steel. The upper level of the oxygen content of 0.015% due neo is a need to ensure the required level of ductility of steel and the bottom 0.001%, respectively - the need to ensure the required level of strength and machinability of the steel.

Ratio

The ratio of oxygen/calcium=1÷4.5 is responsible for the formation of the sandwich nonmetallic inclusions. When this upper limit of the ratio(s) - oxygen content of 4.5 due to the need to ensure the required level of ductility of steel, and the bottom - 1, respectively - the possibility of formation of two-layer sandwich of non-metallic inclusions.

The ratio of calcium/sulfur≥0.065% defines the terms of globular inclusions (sulphides). If this ratio, the globular sulfides, otherwise in steel are elongated sulfides, which increases the anisotropy of the properties of steel and worsens the ratio of the strength-toughness, particularly in the transverse direction of the car.

Comparative analysis of the prototype allows us to conclude that the claimed composition differs from the known introduction of new components - aluminium, calcium and oxygen, as well as ratios: oxygen/calcium=1÷4.5 and calcium/sulfur≥0.065%.

Analysis of patent and scientific and technical information not found solutions with the same set of features, which would reach a similar effect - increasing kharakteristikasetevojj cutting while maintaining a favorable balance of strength and ductility and toughness of steel.

An example implementation of the present invention, without excluding others, in the scope of the claims.

Smelting of the investigated steel (chemical composition, wt.%: carbon - 0.40%, manganese - 0.65%, silicon - 0.32%, chromium - 0.92%, vanadium - 0.01%, sulfur - being 0.036%, calcium - 0.0024%, oxygen - 0.007%) was performed in a 150-ton electric arc furnaces (EAF-150, power transformer 80 MV·A) using the charge 60% of DRI pellets and 40% of scrap metal that provides the mass fraction of nitrogen before the release of the DSP is not more of 0.003%and a low content of non-ferrous impurities. Pre-alloying metal to manganese and silicon were carried out in the ladle with the release of DSP (Release in the bucket perechislennogo metal. The deoxidation of metal with the release of aluminum, ferrosilicon - deoxidation, alloying - FeMn(SiMn), FeCr). After graduation spent a metal blowing argon through the bottom vent unit 5-7 minutes Then vacuum into the vacuum degasser, doping (thin) - carbon, manganese and silicon. After degassing treatment in a ladle furnace. For 15-30 minutes before the end of the processing is injected oxidant, in this case - oxidized pellets. Then again injected aluminum (wire). 10-15 minutes processing cored wires with silicocalcium and clean grey. The casting was carried out on bars, the LDCs radial type in NLS 300× 360 mm with a speed of extrusion of 0.6-0.7 m/min When the casting was carried out to protect streams from the secondary oxidation as follows:

- a steel ladle-tundish - submersible pipe with a flow of argon

the intermediate ladle - slag-forming mixture

the tundish into the mold is submerged nozzle (coronagraphy)

- in the mould - slag-forming mixture.

After casting and cut-to-length the length of continuously cast billets were cooled in the furnace controlled cooling. Next, the ingots are rolled on the mill 700 in billet (square 170 mm). All the original procurement was edited, cleaned from scale, control surface. Heating billets before rolling was carried out in two reheating furnaces, walking beam furnace. The heating temperature of the workpiece 900°With that reduced power consumption by 15 % and significantly reduces the decarburization of the steel. Scale from the surface of the workpiece was removed by high pressure water on the water descaling unit. Rolling were in continuous lines - small-and medium section. High rigidity stands, auto negotiation speed trains, the system loop in finishing light section lines allowed us to get the car high precision. The finish of the car was made out of thread. Finish included, editing control surface defects and ultra audible control internal defects, custom abrasive cleaning, solid abrasive grinding, turning round bars of steel. The accuracy of the car after turning corresponds to the quality h11. At the "RIOT-ROD" from coils of hot-rolled get grinded bars up to 6 meters with precision cutting ±5 mm

In the hot rolling get rolled diameter of 21 mm with the structure of granular perlite (99%), de-carbonized layer depth of 0.09 mm, score the actual grain - 8, cold sludge wire with a diameter of 21 mm, 67%of the temporary strength of 580 MPa, an elongation of 21%, narrowing 63%.

Ratio

oxygen/calcium=2.92: calcium 0.0024%, oxygen 0.007%, calcium/sulfur= 0.067 calcium 0.0024%, sulfur being 0.036% the introduction of the proposed method of production of long-rolled products from medium carbon steel high machinability, providing a two-layer sandwich of non-metallic inclusions, guaranteeing, on the one hand, ensuring high performance cutting, on the other hand, a favorable ratio of strength ductility and toughness of steel.

Rolled, round, made of medium-carbon steel containing carbon and alloying elements that have the specified quality parameters become non-metallic inclusions, p is ctory, mechanical properties and hardenability and machinability, characterized in that the steel contains the following ratio of components, wt.%:

Carbon0,35-0,42
Manganese0,50-0,80
Silicon0,17-0,37
Chrome0,80-1,10
Sulfur0,020-0,040
Vanadiumof 0,005 0,020
Calcium0,001-0,010
Oxygen0,001-0,015
NickelTo 0.25
CopperNot more than 0,25
MolybdenumNot more than 0.10
ArsenicNot more than 0.08
NitrogenLess than 0.015
Iron and
inevitable impuritiesRest

when performing correlations

oxygen:calcium=1÷4,5; calcium:sulfur ≥0,065,

the maximum score of contamination of steel, non-metallic inclusions in sulfides having a two-layer structure, oxides, silicates and nitrides of not greater than 3 points for each type of inclusions, car has a homogeneous spheroidizing structure in length, consisting of not less than 80% zernistos the perlite, the amount of the actual grain 5-10 point, diameter 10÷30 mm, de-carbonized layer is not more than 1.5% of the diameter, the amount of cold upsetting of not less than 1/3 of the height, ultimate strength, not more than 600 MPa, elongation not less than 18%, the relative narrowing of at least 60%.



 

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2 cl, 4 tbl

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FIELD: metallurgy; production of round calibrated bars from medium-carbon steel of high machinability for manufacture of shock absorber rods.

SUBSTANCE: proposed method includes making steel in electric-arc furnace, off-furnace treatment, micro-alloying with sulfur, continuous teeming at protection of jet with argon, hot rolling of continuously cast billet making use of mechanical heat treatment modes, hot calibration and winding merchant shape in bundles, unwinding bars, cutting and straightening bars. Steel contains the following components, mass-%: carbon, 0.42-0.50; manganese, 0.50-0.80; silicon, 0.17-0.37; sulfur, 0.020-0.040; phosphorus, 0.001-0.030; aluminum, 0.03-0.05; calcium, 0.0010.010; oxygen, 0.001-0.015; chromium, no more than 0.25%; nickel, up to 0.35%; copper, no more than 0.25%; molybdenum, no more than 0.10%; arsenic, no more than 0.08%; nitrogen, no more than 0.015%. The remainder being iron and unavoidable admixtures. Ratio of oxygen and calcium content is determined by the following ratio: oxygen/calcium =1-4.5 and calcium-sulfur ≥0.065. At tapping from melting unit, metal is subjected to deep deoxidation, alloying with silicon, manganese, chromium etc. After bringing the chemical composition of metal to specified level pertaining to all elements, but for aluminum and sulfur, metal and slag are subjected to repeated oxidation with gaseous oxygen or oxidized pellets. Then aluminum is added followed by treatment with calcium and alloying with sulfur.

EFFECT: enhanced conditions for machining articles made from this steel; improved ductility and toughness characteristics of steel.

1 ex

FIELD: metallurgy; production of merchant shapes from medium-carbon steel at high machinability for manufacture of shock absorber rods for automobiles.

SUBSTANCE: proposed method enhances machinability at optimum ratio of strength, ductility and plasticity, minimum level of anisotropy at simultaneous improved characteristics of hardenability to level of through hardenability of rods to 30 mm. Proposed bars are made from medium-carbon steels containing carbon and alloying elements and possessing preset parameters of metallurgical quality, structure, mechanical properties, hardenability and machinability; medium-carbon steel contains the following components, mass-%: carbon, 0.42-0.50; manganese, 0.50-0.80; silicon, 0.17-0.37; sulfur, 0.020-0.040; phosphorus, 0.001-0.030; aluminum, 0.03-0.05; calcium, 0.001-0.010; oxygen, 0.001-0.015; chromium, no more than 0.25; nickel, no more than 0.025; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than0.08; nitrogen, no more than 0.015; the remainder being iron and unavoidable admixtures. Ratio of oxygen and calcium , as well as calcium and sulfur is determined by the following dependances: oxygen/calcium= 1-4.5 and calcium/sulfur≥0.065. Nonmetallic inclusions of sulfides have double-layer structure: sulfide with oxide envelope; curvature of bars does not exceed 1.0 mm/m; rolled bars have plastic ferrite-pearlite structure at actual size of grain of 5-8; diameter of bars ranges from 10 to 30 mm; decarbonized layer is no more than 1.5% of diameter; hardness of billet is 229-255; rupture strength no less than 640 Mpa; relative elongation no less than 6% and relative reduction no less than 30%.

EFFECT: improved machinability characteristics at optimum ductility and strength; improved hardenability characteristics.

1 ex

FIELD: metallurgy, namely production of rolled bars.

SUBSTANCE: round rolled bar is made of steel containing, mass %: carbon, 0.17 -0.23; manganese, 0.65 -0.95; silicon, 0.17 - 0.37; chrome, 0.35 - 0.65; nickel, 0.40 - 0.75; molybdenum, 0.15 -0.25; sulfur, 0.020 - 0.040; phosphorus, 0.001 - 0.010; oxygen, 0.001 -0.015; copper, no more than 0.25; arsenic, no more than 0.08; nitrogen, no more than 0.015; iron and inevitable impurities, the balance; at relations oxygen/calcium = 1.45; calcium/sulfur ≥ 0.065. Rolled bar contains double-layer structure sulfide - sulfide with oxide envelope and it has hardness after quenching in depth 6 mm 32 - 40 HRc, size of real grain 5 - 10 points, diameter - up to 50 mm. Rolled bar has no decarbonized layer. After quenching and tempering rolled bar is characterized by temporary tensile strength, 1180 - 1520 MPa; limit yield, no less than 930 MPa; percentage elongation, no less than 7%; percentage tapering, no less than 59%.

EFFECT: improved cutting capability, enhanced hardenability at keeping high technological ductility.

1 ex

FIELD: metallurgy; methods of production of the circular bars.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to production of circular hot-rolled hot-calibrated and turned bars made out of the medium alloy steel of the heightened cutability used for manufacture of the high-loaded pinion gears of the car gearbox. The technical result of the invention is production of the structure of the bar ensuring the rational cutting conditions, which will allow to provide the guarantied level of the consuming properties of the pinion gears of the car gearbox. The method of production of the circular bar made out of the medium alloy steel includes: smelting of the steel in the electric furnace, out-of-furnace treatment of the steel in the ladle with a doping, a reduction and blowing by argon, the steel degassing treatment, the continuous steel casting, the hot rolling of the continuous bars with usage of modes of the thermomechanical treatment. According to the invention after the steel degassing conduct the repeated ladle metal reduction by the oxygenated pellets with the subsequent addition of aluminum, sulfur and produce the steel at the following ratio of the components(in mass %): carbon - 0.17-0.23; manganese - 0.65-0.95; silicon - 0.17-0.37; chromium - 0.35-0.65; nickel - 0.40-0.75; molybdenum - 0.15-0.25; sulfur - 0.020-0.040; phosphor - 0.001-0.035; niobium - 0.005-0.02; vanadium - 0.005-0.08; calcium - 0.001-0.010; oxygen - 0.001-0.015; copper - no more than 0.25; arsenic - no more than 0.008; nitrogen - no more than 0.015; iron and the imminent impurities - the rest; at realization of the following ratios: oxygen/calcium = l÷4.5 and calcium/sulfur ≥ 0.065. After the hot rolling realize the finish of the bars including the straightening, monitoring of the surface defects, the selective abrasive cleaning, the whole-size continuous abrasive grinding, turning of the circular bars, reeling of the bars in bundles and cutting the bars into billets of up to 6 meters length with the cutting accuracy ±5 mm.

EFFECT: the invention ensures production of the bars with the structure providing the rational cutting conditions, which guaranty the required level of the consuming properties of the car gearbox pinion gears.

FIELD: ferrous industry; production of stainless steel of the martensitic-austenitic class.

SUBSTANCE: the invention is pertaining to the field of ferrous industry, to production of stainless steel of the martensitic-austenitic class intended for manufacture of the high-loaded components working on twisting and bending under a dynamic loading in corrosive acid mediums having a high content of salts of alkaline and alkaline-earth metals, salts of nitrogenous acid and sulfuric acid, ions of chlorine and hydrogen sulfide. The steel contains the following ingredients(in mass %): Carbon - 0.005 - 0.07; silicon - no more than 1.0; manganese - no more than 1.8; chrome - 12.5 - 17.0; nickel - 2.0 - 8.0; molybdenum + 3 · tungsten - 0.05 - 5-4.5; nitrogen - 0.005 - 0.15; boron - 0.0001 - 0.01; at least one the following ingredients: aluminum, titanium, niobium, vanadium - 0.01 - 5.0; iron and impurities - the rest. At that Thus (Mo+3·W)≤(kl-Cr·al), where kl=15.9, a1 = 0.87, and alsoNi=k2-a(Cr+Mo+W), wherek2 = 16.25 ± l.5, a2=0.7 ± 0.l. The method of manufacture of the product provides for ingots casting or blanks continuous casting, rolling and thermal treatment. The technical result of the invention is an increased steel plasticity, its corrosion resistance in hydrosulfuric mediums with a simultaneous increase of stability of the steel mechanical properties.

EFFECT: the invention ensures an increased steel plasticity, corrosion resistance in hydrosulfuric mediums, stability of the steel mechanical properties.

25 cl, 2 tbl, 1 ex

FIELD: ferrous metallurgy; production of the corrosion-resistant steel and products made out of it.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, to production of the corrosion-resistant stainless steel of the martensitic- austenitic class intended for manufacture of the high-loaded component parts working on torsion and bending under a dynamic loading in corrosive acidic mediums with the high content of salts of alkaline and earth metals, salts of nitrogenous and sulfuric acids, ions of chlorine, hydrogen sulfide. The corrosion-resistant steel contains ingredients in the following ratio (in mass %): Carbon - no more than 0.07; chrome - 12.5-17.0; nickel - 2.0-8.0; molybdenum +3 x tungsten - 0.05-4.5; iron and impurities - the rest. At that (Mo+3·W)≤(k1- Cr·a1), where k1=15.9, a1=0.87, and also Ni=k2-a2 (Cr+Mo+W), wherek2=16.25±l.5, a2=0.7±0.1. The technical result of the invention is an increase of pliability, optimal corrosion resistance and strength in the hydrosulfuric mediums with a simultaneous increase of stability of the steel mechanical properties.

EFFECT: the invention ensures an increase of pliability, optimal corrosion resistance and strength in the hydrosulfuric mediums with a simultaneous increase of stability of the steel mechanical properties.

25 cl, 2 tbl, 1 ex

FIELD: metallurgy; production of important rolled stock for oil-well tubing of increased service life.

SUBSTANCE: proposed method includes making steel of definite chemical composition in electric furnace, tapping metal from furnace into ladle, treatment of metal in ladle and teeming steel into ingot molds. Alloying with molybdenum is performed by introducing molybdenum-containing materials into furnace in making steel. After teeming, ingots are rolled, cooled and heated for rolling in preset temperature range and are subjected to preliminary and final deformation; process is completed by final cooling of rolled blanks to surrounding temperature.

EFFECT: improved strength characteristics and cold resistance of metal; enhanced reliability of metal products.

1 ex

FIELD: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from medium-carbon high-plasticity steel composed of, wt %: carbon 0.27-0.32, manganese 0.30-0.50, silicon 0.01-0.37, chromium 0.01-0.25, sulfur 0.005-0.020, niobium 0.005-0.02, calcium 0.001-0.010, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 12/C-Mn/0.03 ≥ 20, Ca/S ≥ 0.065, rolled iron has following characteristics: maximum degree of pollution with nonmetal inclusions, in particular sulfides, oxides, silicates, and nitrides, does not exceed 3 points for each type of inclusions; longitudinally uniform spheroidized structure composed of at least 80% grainy perlite; effective grain size 5-10 points; diameter 10-30 mm; carbon-free layer not exceeding 1.5% diameter; cold setting value at least 1/3 height; point of maximum load not higher than 620 MPa; relative elongation at least 18%; and relative contraction at least 55%.

EFFECT: ensured optimal conditions for cold die forging of high-strength geometrically complex fastening members and simultaneously ensured improved characteristics of in-process plasticity and low level of stray hardening.

FIELD: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from low-carbon steel composed of, wt %: carbon 0.17-0.25, manganese 0.30-0.65, silicon 0.01-0.17, sulfur 0.005-0.020, vanadium 0.005-0.07, niobium 0.005-0.02, calcium 0.001-0.010, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 12/C-Mn/0.02 ≥ 27; 0.46 ≥ 6V+8Nb ≥ 0.22; Ca/S ≥ 0.065, rolled iron has following characteristics: maximum degree of pollution with nonmetal inclusions, in particular sulfides, oxides, silicates, and nitrides, does not exceed 3 points for each type of inclusions; longitudinally uniform spheroidized structure composed of at least 80% grainy perlite; effective grain size 5-10 points; diameter 10-25 mm; carbon-free layer not exceeding 1.5% of diameter; cold setting value at least 1/3 height; point of maximum load not higher than 550 MPa; relative elongation at least 20%; and relative contraction at least 60%.

EFFECT: ensured optimal conditions for cold die forging of high-strength geometrically complex fastening members and simultaneously ensured improved characteristics of in-process plasticity and low level of stray hardening.

FIELD: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from alloyed steel composed of, wt %: carbon 0.06-0.11, manganese 0.30-0.9, silicon 0.001-0.15, boron 0.0005-0.0050, vanadium 0.005-0.08, aluminum 0.02-0.06, titanium 0.01-0.04, sulfur 0.005-0.020, nitrogen 0.005-0.015, calcium 0.001-0.010, iron and unavoidable impurities - the balance. When following relationships are fulfilled: Ti/48+Al/27-N/14 ≥ 0.6 x 10-3; Mn+5.0C ≥ 0.80; Ca/S ≥ 0.065, rolled iron has following characteristics: maximum degree of pollution with nonmetal inclusions, in particular sulfides, oxides, silicates, and nitrides, does not exceed 3 points for each type of inclusions; longitudinally uniform spheroidized structure composed of at least 60% grainy perlite; effective grain size 5-10 points; diameter 10-16 mm; carbon-free layer not exceeding 1.0% of diameter; cold setting value at least 1/3 height; throughout hardenability in circles up to 16 mm in diameter; point of maximum load not higher than 500 MPa; relative elongation at least 22%; and relative contraction at least 70%.

EFFECT: ensured optimal conditions for cold die forging of high-strength geometrically complex fastening members and simultaneously improved steel hardenability characteristics.

FIELD: rolled tube production, namely method for making pilger mill mandrels from heat resistant steel for rolling hot rolled tubes.

SUBSTANCE: method for making mandrels used for rolling hot rolled tubes with large and mean diameters in range 273-550mm comprises steps of casting ingots of hear resistant steel; forging cylindrical solid or hollow blanks, roughly working of them, performing heat treatment and finishing mandrels at forming conicity 1 - 2 mm on length of their working portion while taking into account designed linear expansion coefficient during rolling process; determining diameter size by means of expression δ = dn - Δ/1 + αĚt. One portion of mandrel from lock along length of half of working portion of mandrel is in the form of cone with diameters of cone bases determined form given expression and second portion is in the form of cylinder or truncated cone whose diameters are determined according to next expression

EFFECT: lowered lengthwise thickness difference of tubes.

3 cl, 1 dwg, 1 tbl

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