Corrosion-resistant steel and the product made out of it

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

 

The invention relates to ferrous metallurgy, in particular to products made of steel, as well as stainless steel martensitic-austenitic, which is designed for the production of highly loaded parts operating in torsion and bending under dynamic loading and in aggressive acidic media with a high content of salts of alkali and alkaline earth metals, salts of nitric and sulphuric acids, ions of chlorine, hydrogen sulfide. Known steel of the following composition, in wt.%:

carbon0,01-0,07
silicon0,4-0,8
manganese0,4-0,8
chrome15,0-17,0
Nickel2,5-4,5
copper1,6-3,0
niobium0,15-0,35
ironrest

(see RU # 2215815 C1, 10.11.2003,)

Known for a variety of steel products, for example, stainless chromium-Nickel steel of high strength and ductility, which is used in the production of cold-rolled strip, strips, sheet, high strength wire ropes, springs, medical tools, cutting tools, fasteners, parts, constructions, etc. high-Strength corrosion-resistant products made of steel next to the rod components wt.%: carbon 0.15 to 0.45, and chrome to 12.0-16.5, and Nickel 3,0-5,0, iron rest, the content of carbon and Nickel is in the following dependencies: chrome =25,7-(17,5°18,0) carbon - (1,2°1,4) Nickel (see, for example, RU 2061781 C1, 10.06.1996, 6 With 22 38/40).

The prior art also know the product is made from high-strength corrosion-resistant steel, austenitic-martensitic class, hardening with nitrogen, intended for the production of highly loaded machine parts, in particular of aircraft operating at the temperature of minus 70°to 300°in any climatic conditions (see, for example, RU 2214474 C2, 20.10.2003, 7 With 22 38/48).

A disadvantage of the known products of corrosion-resistant steels is insufficient plasticity and instability steel structure with a low corrosion resistance, primarily in hydrogen sulfide environments, resulting in over time during operation of the mechanical properties of steel products can be much worse.

The problem solved by the invention is the creation of a corrosion-resistant steel and articles thereof, having high ductility, optimum corrosion resistance and strength, primarily in hydrogen sulfide environments, while enhancing the stability of the mechanical properties of steel during the operation.

This task became part is solved by the fact corrosion-resistant steel, according to the invention contains the components in amounts of, in wt.%:

carbonnot more than 0.07
chrome12,5÷17,0
Nickel2,0÷8,0
molybdenum+3·Wolfram0,05÷4,5
iron and impuritiesrest

provided that the content of its components satisfies the following formula (Mo+3·W)÷(k1-Cr·a1), where k1=15,9, a1=0,87, and Ni=k2-a2·(Cr+Mo+W), where k2=16,25±1,5, a2=0,7±0,1.

The steel may further contain copper in amounts of 0.05÷5,0) wt.%.

The steel may further contain silicon in an amount of not more than 1.0 wt.%.

The steel may further contain manganese in an amount of not more than 1.8 wt.%.

The steel may further contain nitrogen (0,005÷0.15) wt.%.

The steel may further contain boron in the amount of (0,0001÷0,01) wt.%. The steel may further contain at least one from the group:

aluminum, titanium, niobium, vanadium in the amount of (0,01÷5,0) wt.%.

The steel may contain at least one of the following additional components: calcium, cerium, barium, rare earth metals, zirconium, yttrium, magnesium, arsenic, t is ntal, selenium.

Each additional component may be contained in the amount of (0,001÷0,1)wt.%.

The steel may further comprise lanthanum in number (0,005÷0,02) wt.%.

The steel may further contain cobalt in an amount of not more than 1.0 wt.%.

The specified task is in part the product of the steel is solved due to the fact that the product is made of corrosion-resistant steel according to the invention, made mainly in the form of a cylindrical rod received after at least one heat treatment in the following modes: heating and drying at a temperature of (300÷650)°C for 1÷17 hours with subsequent cooling in air or in an environment with high cooling capacity, for example water or oil, and the product is made of the above-described steel.

The product can be manufactured with a diameter of from 12 to 45 mm

The product can be manufactured length up to 8.5 meters.

The roughness of its surface Ramay be not more than 2.5 μm on a reference length of 0.8 mm

The product may have a yield strength of not less than 90 kgf/mm2.

The product may have a deviation from straightness of not more than 0.2 mm per meter length of the product.

The hardness of the product may be 444-285 HB when the diameter of the imprint of 2.9 to 3.6 mm

The product may be in the form of a fastener with a thread, for example the bolt is, screw or stud size from M5 to M20 with right or left threaded applied by the method of knurling or threading.

The bolt or screw can be made with the head, planted in hot or cold.

The product can be obtained by rolling ingots or continuously cast billets.

Rolling can be carried out in two stages: the first stage on the blooming obtaining billets mainly of square section, and then on the bar mill - on billet predominantly cylindrical shape.

The side of the billet may be from 80 to 120 mm, and the diameter of cylindrical workpieces to be predominantly from 12 mm to 45 mm

The product may be in the form of a shaft, for example, a submersible pump or separator.

The technical result is corrosion-resistant steel and the product that has a high plasticity, optimum corrosion resistance and durability in aggressive, primarily in hydrogen sulfide environments, while enhancing the stability of the mechanical properties of steel during operation due to the optimally chosen ratios of components of steel and modes of treatment products.

So, molybdenum and tungsten are introduced into the steel in these quantities with the aim of improving the corrosion resistance, the person is but to pitingolo corrosion. In this sense, the influence of molybdenum and tungsten equivalent. Tungsten has a much higher atomic weight 183.85) compared with molybdenum (at 45.44). In paragraph 6 of the notes to the table 1 GOST 4543-71 the possibility of replacing the items from the calculation of the three weight parts of tungsten per weight part of molybdenum.

Tungsten due to the larger size of the atom introduces more distortion in the crystal lattice of iron compared to molybdenum. This can improve the strength properties of steel and from this point of view, the use of tungsten is preferable.

On the other hand, tungsten and molybdenum expensive items, as well as when alloying with tungsten steel requires three times more than that of molybdenum, the use of tungsten for alloying can lead to a considerable rise in prices of steel.

Molybdenum, tungsten and chromium belong to territooriumil elements. While alloying steel Mo, W, Cr at the upper limit of their content of steel can go in the ferritic-austenitic class instead of a martensitic-austenitic class.

The ratio of (Mo+3W)≤(k1-Cr/a1) restricts the upper limit of the content of Mo and W, depending on the number entered chromium. This excludes the transition began in ferritic-austenitic class.

The second formula Ni=k2-a2(Cr+Mo+W) establishes a relationship between austenite anousim element Ni and territooriumil elements Cr, Mo, W. the conditions of the formula also allows obtaining of steel martensitic-austenitic class.

K2has the range of values of k2min=14,75 and k2max=17,75. If the value of the Nickel will be lower than calculated when k2minthe steel acquires a martensitic or martensitic-ferritic structure with reduced plastic properties.

When the Nickel content is more calculated when k2maxsteel turns austrina-martensitic structure containing austenite more than 30%. This results in reduced mechanical properties of steel.

Thus, the Nickel content in the steel depends on the number territooriumil elements and is determined by the formula Ni=k2-a2(Cr+Mo+W), where a2- correction factor.

High strength steel can be provided and martensitic-ferritic steel structure, as, for example, in the steel according to the patent RU 2215815. In this case, when the same chromium content (territooriumil elements) required a lower Nickel content (austintoebosch elements).

At the same time, Nickel - flexible, corrosion-resistant element. Increasing the Nickel content in the steel we give it more flexibility, which can be characterized by the following parameters: elongation, relative narrowing, impact strength, resistance from the Ali to cyclic fatigue, etc., as well as improving corrosion resistance, primarily in hydrogen sulfide environments.

Of equal strength due to approximately equal content of martensite. In the first case, as the excess phase contains ferrite, the second austenite.

The carbon in the steel to form chromium carbides, which in the case of the carbon content of more than 0.07% significantly degrade the ductility of the steel and toughness. You must strive for the minimum carbon content.

When the chromium content of less than 12.5% rapidly deteriorating corrosion resistance of steel. When the chromium content of more than 17% in the steel is the formation of additional phase-ferrite. This results in reduced mechanical properties of steel, deteriorating ductility.

The required level of mechanical properties of steel products ensures these conditions of heat treatment of the dispersion hardening.

Properties of precipitation hardening steel are determined by the number and dispersion of released intermetallic particles. At a temperature of less than 300°processes are slow. Insufficient removed the source voltage of martensite. As a result, the steel does not acquire the required strength, but because notusing martensite in the future when operating products possible breakage.

At temperatures close to, but exceeding 300°With, because slow is rotamania processes require significant exposure to 17 hours to get a noticeable hardening.

With increasing temperature the intensity of formation of intermetallic particles increases, the steel acquires greater strength. The maximum strength of the steel reaches at 450-500°C. At higher temperatures the intermetallic compounds are highlighted in larger sizes. When this is achieved the strength of the steel is reduced, and minimum required strength is achieved at a temperature not exceeding 650°C.

If the shutter speed is less than 1 hour, the number of intermetallic particles will be insufficient for appreciable hardening steel at all temperatures.

At a speed of more than 17 hours, the growth of spin-off intermetallic particles, resulting in a decrease in the strength of the steel.

Possible and repeat the process of heat treatment on the above-mentioned mode in which the strength of steel turns out the same, but in the case of a double heat treatment above the level of plastic properties and impact toughness of the steel.

Thus, the proposed steel product, and a method of manufacturing steel products provide greater flexibility while maintaining high strength, their stability during operation, as well as resistance to stress corrosion cracking under stress while working in hostile environments.

Example.

Steel was smelted in the main arc ele is tropici. Casting was carried out in the bars of 1.15 T. the Ingots were rolled on the blooming on the workpiece 100 mm square Billets were rolled on the bar mill on the rods with a diameter of 20 mm and a length 5400 mm Heat treatment rods was double the leave on the following modes:

- heating and self-control rods at a temperature of 600°C for 4 hours followed by air cooling;

repeated heating and endurance bars at a temperature of 600°C for 4 hours followed by air cooling.

The finished bars were determined mechanical properties.

Testing of mechanical properties was carried out according to GOST 1497-43, toughness according to GOST 9454-78.

The resistance of steel to stress corrosion cracking under tension in hydrogen sulphide was performed according to the method of NACE standard TM 0177-96 (USA). The sample was placed in an aqueous solution of hydrogen sulfide and it was applied tensile stress, which created tension in the metal, equal to 70% of the steel yield strength. The resistance of steel to stress corrosion cracking under tension in hydrogen sulphide was determined as the time elapsed from the beginning of the test to the complete destruction of the sample. The chemical composition of the steel produced with different content components, the test results of mechanical properties and corrosion tests are given in the table is Ah 1, 2.

Table 1

Chemical composition of steel
Option
Chem. composition123456
carbon0,0150,070,0050,0150,0150,015
chrome151515151517
Nickel*fact52,47,21,96,83
calculationfrom 2.1 to 6.12,4-5,4from 4.2 to 7.2from 2.1 to 6.1from 2.1 to 6.12,0-5,0
molybdenum1,52,550,02 1,51,51,2
Wolfram0,10,10,010,10,10,1
molybdenum+ 3·Wolframfact1,82,850,051,81,81,5
calculation≤2,85≤2,85≤2,85≤2,85≤2,85≤1,1
*) In table 1 for the specified components in addition to the actual content of the components in the embodiments of the steel composition are calculated required by the formula of their values.
Table 2

Mechanical and corrosion properties of steel
Option
Properties123456
Yield strength, kg/mm2 125120128125100115
Temporary tear resistance, kg/mm2130127132130110120
Relative narrowing,%605860506055
Elongation,%201820122017
Impact strength, j/cm212011012080120100
Corrosion resistance of steel under tension, h800750800700800760

Options 1, 2, 3 correspond to the invention. Option 1 - optimum. Options 4, 5 - does not meet present invention, as the Nickel content beyond the boundaries of the AMI defined by the formula. In the option 4 has lower values of ductility and corrosion resistance, because the steel was purely martensitic, and option 5 has lower strength properties due to the excessive content of austenite.

Option 6 has a molybdenum content+3* tungsten over a certain formula. Steel has a high content of ferrite and residual austenite and, consequently, reduced strength and plastic characteristics.

1. Corrosion-resistant steel, characterized in that it contains the components in amounts, wt.%:

Carbonnot more than 0.07
Chrome12,5÷17,0
Nickel2,0÷8,0
Molybdenum+3·Wolfram0,05÷4,5
Iron and impuritiesRest

provided that the content of its components satisfies the following relationships:

(Mo+3·W)≤(k1-Cr·a1), where k1=15,9, a1=0,87, and

Ni=k2-a2(Cr+Mo+W), where k2=16,25±1,5, a2=0,7±0,1.

2. The steel according to claim 1, characterized in that it additionally contains copper in an amount of 0.05÷5.0 wt.%.

3. The steel according to claim 1, characterized in that it further contains silicon in a quantity which as not more than 1.0 wt.%.

4. The steel according to claim 1, characterized in that it further contains manganese in an amount of not more than 1.8 wt.%.

5. The steel according to claim 1, characterized in that it further contains nitrogen in an amount of 0.005÷to 0.15 wt.%.

6. The steel according to claim 1, characterized in that it further contains boron in an amount of 0.0001÷0.01 wt.%.

7. The steel according to claim 1, characterized in that it further comprises at least one from the group of: aluminum, titanium, niobium, vanadium in an amount of 0.01÷5.0 wt.%.

8. The steel according to claim 1, characterized in that it contains at least one of the following additional components: calcium, cerium, barium, rare earth metals, zirconium, yttrium, magnesium, arsenic, tantalum, selenium.

9. The steel of claim 8, wherein each additional component is contained in an amount of 0.001÷0.1 wt.%.

10. The steel according to claim 1, characterized in that it further comprises lanthanum in an amount of 0.005÷0.02 wt.%.

11. The steel according to claim 1, characterized in that it further contains cobalt in an amount of not more than 1.0 wt.%.

12. The product of corrosion-resistant steel, characterized by the fact that it is made mostly in the form of cylindrical rod received after at least one heat treatment in the following modes: heating and drying at a temperature of 300÷650°C for 1÷17 h with subsequent cooling gap is a discussion on air or in the environment with increased cooling capacity, for example water or oil, and the product is made of steel according to any one of claims 1 to 11.

13. The product according to item 12, characterized in that it is made with a diameter of from 12 to 45 mm

14. The product according to item 12, characterized in that it is manufactured length up to 8.5 meters

15. The product according to item 12, characterized in that the roughness of its surface Ranot more than 2.5 μm on a reference length of 0.8 mm

16. The product according to item 12, characterized in that it has a yield strength of not less than 90 kgf/mm2.

17. The product according to item 12, characterized in that it is the deviation from straightness of not more than 0.2 mm per meter length of the product.

18. The product according to item 12, characterized in that its hardness is 444-285 HB when the diameter of the imprint of 2.9 to 3.6 mm

19. The product according to item 12, characterized in that it is made in the form of a fastener with a thread, such as a bolt, screw or stud, size from M5 to M20 with right or left-handed, applied by the method of knurling or threading.

20. The product according to claim 19, characterized in that the bolt or screw is made with the head, planted in hot or cold.

21. The product according to item 12, characterized in that it is obtained by rolling ingots or continuously cast billets.

22. The product according to item 21, wherein the rolling carried out in two stages: the first stage on the blooming obtaining billets mainly of square section, and then on the bar mill - on procurement predominantly cylindrical shape.

23. The product according to item 22, wherein the side of the billet is from 80 to 120 mm

24. The product according to item 22, wherein the diameter of cylindrical workpieces is mainly from 12 to 45 mm

25. The product according to item 12, characterized in that it is made in the form of a shaft, such as a submersible pump or separator.



 

Same patents:

FIELD: chemical pickling of metal materials; treatment of surfaces made from austenitic stainless steels and articles made from such steels, for example, strips, bars, sheets and pipes.

SUBSTANCE: proposed method includes removal of adequate amount of material from steel surface by acid pickling for obtaining surface with crevice corrosion at critical temperature exceeding x, where x (°C)= 3.2 (mass-% Cr)+7.6 (mass-% Mo)+10.5 (mass-% N)-88.5. Austenitic stainless steel has equivalent number of resistance to pitting corrosion not exceeding 52.6 at critical temperature of at least 38°C. Material may be removed from part of surface by any method, including sandblasting by abrasive particles, grinding and/or acid pickling under more aggressive conditions as compared with usual treatment of such steels.

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26 cl, 8 dwg, 4 tbl

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2 cl, 3 tbl, 1 ex

FIELD: metallurgy, in particular stainless steel excellent in cutting workability useful in stick parts manufacturing with very high cutting speed.

SUBSTANCE: invention relates to resulfurizated austenitic stainless steel excellent in workability and corrosion resistance containing calcium oxide silicoaluminate inclusions of anortite and/or pseudowollastonite and/or gelenite-type, associated with inclusions of CrMnS, comprising 30-70 wt.% of chromium.

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FIELD: metallurgy, in particular steel for manufacturing of crossing frog of railroad and tram rails.

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1 tbl, 1 ex

FIELD: iron metallurgy, steel for manufacturing of heavy loaded products, in particular gear hardening by cementation.

SUBSTANCE: claimed steel in one embodiment contains (mass %) carbon 0.12-0.26; manganese 0.7-1.5; silicium not more than 0.4; chromium 0.4-1.2; nickel 0.4-0.7; molybdenum not more than 0.3; sulfur 0.01-0.05; and balance: iron and inevitable impurities, wherein total content of manganese and chromium is at least 1.6 mass %. In the second embodiment steel contains (mass %) carbon 0.12-0.26; manganese 0.4-1.2; silicium not more than 0.4; chromium 0.4-1.0; nickel 0.8-1.4; molybdenum not more than 0.3; sulfur 0.01-0.05; and balance: iron and inevitable impurities, wherein total content of manganese and chromium is at least 1.4 mass %. In the third embodiment steel contains (mass %) carbon 0.12-0.26; manganese 0.4-1.0; silicium not more than 0.4; chromium 0.4-1.0; nickel 1.5-2.0; molybdenum not more than 0.3; sulfur 0.01-0.05; and balance: iron and inevitable impurities, wherein total content of manganese and chromium is at least 1.1 mass %.

EFFECT: steel with improved hardenability without losses of cutting workability and efficiency of steel alloying.

4 ck, 2 tbl, 5 ex

FIELD: flexible pipe manufacture.

SUBSTANCE: invention relates to using stainless steel for manufacturing pipes for developing offshore oil and gas fields and claims using ferrite-austenite alloy containing, wt %: carbon up to 0.05, silicon up to 0.8, manganese 0.30-1,5, chromium 28.0-30.0, nickel 5.80-7.40, molybdenum 2.00-2.50, nitrogen 0.30-0.40, copper up to 1.0, tungsten up to 2.0, sulfur up to 0.010, and iron - the rest. 30 to 70% of the alloy is constituted by ferrite and the rest by austenite. Alloy is used for manufacturing flexible cable pipes to be laid on the marine bottom in the course of development of oil and gas fields. Yield point of the alloy on stretching is at least 750-850 MPa and relative elongation at least 25%. Manufacture of seamless pipes is accomplished by extrusion followed by hot rolling and annealing for 3-10 min at 1040-1080°C. Pipes are welded line-on-line and coiled on drum.

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5 cl, 2 dwg, 8 tbl, 2 ex

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

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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: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from alloyed steel composed of, wt %: carbon 0.28-0.35, manganese 0.90-1.40, silicon 0.001-0.37, sulfur 0.005-0.020, chromium 0.001-0.35, vanadium 0.001-0.07, molybdenum 0.001-0.10, nickel 0.001-0.10, niobium 0.005-0.02, titanium 0.01-0.04, boron 0.0005-0.0050, aluminum 0.02-0.06, nitrogen 0.005-0.015, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 12/C-Mn/0.055 ≤ 2.0; 500(Ti/24-N/7)+0.2 ≥ 0; 40 ≥ C/0.01+B/0.001 ≥ 0.33, 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% perlite; effective grain size 5-10 points; diameter of wire 10-25 mm; carbon-free layer not exceeding 1.5% diameter; cold setting value at least 1/3 height; throughout hardenability in circles up to 23 mm in diameter; point of maximum load not higher than 640 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 improved steel hardenability characteristics.

FIELD: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from steel containing carbon and alloying elements, having specified parameters of metallurgical quality, structure, mechanical properties, hardenability, and in-process plasticity and characterized by being composed of, wt %: carbon 0.17-0.25, manganese 0.90-1.40, silicon 0.01-0.17, sulfur 0.005-0.020, chromium 0.001-0.35, vanadium 0.001-0.07, nickel 0.001-0.10, copper 0.001-0.10, molybdenum 0.001-0.10, titanium 0.01-0.04, boron 0.0005-0.0050, calcium 0.001-0.010, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 22 ≤ 12/C-Mn/0.055 ≤ 47Ni/10Ti+Al ≤ 0.039; 10B-0.01C/N ≥ 1.80, 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% perlite; effective grain size 5-10 points; diameter of wire 10-25 mm; carbon-free layer not exceeding 1.5% diameter; cold setting value at least 1/3 height; throughout (90%) hardenability in circles up to 19 mm in diameter; point of maximum load not higher than 580 MPa; relative elongation at least 18%; and relative contraction at least 60%.

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

FIELD: ferrous metallurgy.

SUBSTANCE: invention provides round-profiled iron smelted from steel containing, wt %: carbon 0.10-0.15, manganese 0.90-1.40, silicon 0.001-0.37, sulfur 0.005-0.020, chromium 0.001-0.35, nickel 0.005-0.10, niobium 0,005-0.02, titanium 0.01-0.04, boron 0.0005-0.0050, aluminum 0.02-0.06, nitrogen 0.005-0.015, iron and unavoidable impurities - the balance. When following relationships are fulfilled: 500(Ti/24-N/7)+0.2 ≥ 0; 40 ≥ C/0.01+B/0.0001 ≥ 3.0, 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% perlite; effective grain size 5-10 points; diameter of wire 10-23 mm; carbon-free layer not exceeding 2.5% diameter; cold setting value at least 1/3 height; throughout hardenability in circles up to 15 mm in diameter; point of maximum load not higher than 520 MPa; relative elongation at least 20%; and relative contraction at least 65%.

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 + α·t. 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

The invention relates to the field of metallurgy, in particular to the production of rolled low-carbon steel for cold massive forming geometrically-complex fasteners particularly complex form

The invention relates to the field of metallurgy, in particular to the production of rolled low-carbon steel for cold massive forming geometrically-complex fasteners

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 + α·t. 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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