Round-profiled rolled iron from microalloyed high-plasticity steel for cold die forging of high-strength fastening members

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.

 

The invention relates to the field of metallurgy, in particular to the production of rolled, round, micro-high-ductility steel for cold massive forming of high-strength fasteners in the form of pre-hardened from mikrotechna temperature range of hire.

Known rolled, round, micro steel containing carbon and alloying elements having a defined structure, such as cold-deformed martensite, a tensile strength of not less than 1800 MPa, and the wire diameter is 0.1-0.5 mm [1].

Known rolled, round, of medium carbon boron steel, containing (wt.%): carbon 0.06-0.30, si 0.17-1.0, manganese 0.8-2.0, vanadium, 0.01 to 0.25, the nitrogen of 0,005 0,040, boron 0.001-0.008, aluminum from 0.005 to 0.10, titanium 0.005-0.015, the rest of the iron [2]. The disadvantage of this steel are: low technology, insufficient hardenability, wide border element content, which does not allow to ensure the stability properties of steel.

The closest in technical essence and the achieved effect of the present invention is rolled, round, of medium carbon boron steel, containing (wt.%): carbon 0.18-0.24, silica 0,17-0,37, manganese 0.90-1.30, boron 0.0005-0.0050, nitrogen 0.005-0.015, vanadium 0,01-0,08, aluminum 0.02-0.06, titanium 0.01 to 0.04, the rest of the iron when SL is blowing ratio and[3]. The disadvantages of the known steel is too high content of carbon, manganese and silicon, which will not allow to obtain the desired complex consumer properties during deformation hardening in the process of landing a high-strength rod fasteners.

The objective of the invention is the provision of efficient conditions for cold massive forming geometrically-complex high-strength fasteners while providing uniform mechanical properties across the section of the car and high performance hardenability of steel.

The most important requirement of rolled steel, round, boron steel for cold massive forming of high-strength fasteners particularly complex form, is, on the one hand, the high technological plasticity and low coefficient of strain hardening in the state of delivery and, on the other hand, the ability to provide the specified level of consumer properties after the final heat strengthening.

The problem is solved by the fact that known rolled, round, micro, high-ductility steel having a specified structure, ultimate strength and hardness, according to the invention is made of steel containing the following ratio of components, m is S.%:

carbon 0.06-0.11

manganese 0.30-0.9

the silicon of 0.001 to 0.15

boron 0.0005-0.0050

vanadium is 0.005 to 0.08

aluminum 0.02-0.06

titanium 0.01 to 0.04)

sera of 0,005 0,020

nitrogen 0.005-0.015

calcium 0.001-0.010

iron and

inevitable impurities else

And:

the maximum score of contamination of steel, non-metallic inclusions in sulfides, 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 60% granular perlite, the amount of the actual grain - 5-10 point, the wire diameter ranges from 10 to 16 mm, has a de-carbonized layer is not more than 1.0% of the diameter, the amount of cold upsetting of not less than 1/3 of the height, 50% - hardenability in circles with a diameter up to 16 mm, ultimate strength, not more than 500 MPa, elongation not less than 22%, the relative narrowing of at least 70%.

Given the combination of alloying elements (1) allow to obtain in the finished product (bolt, nut, stud diameter up to 16 mm) after thermolysine (tempering temperature of not less than 920°C, followed by tempering temperature not lower than 620° (C) a homogeneous fine structure of martensite leave with a favorable combination of strength and PLA is lichnosti.

Carbon and carbonitrides elements are introduced into the composition of this steel to ensure a fine 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 austenitic region (determines the tendency to grain growth of austenite (up to 950° (C)to stabilize the structure during thermomechanical processing, increases the temperature of recrystallization and, consequently, affects the character γ-α- transformation). Vanadium also contributes to the hardening of steel by heat treatment. The upper limit of the content of carbon (0.11 wt%), vanadium (0.08 wt.%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively, 0.06 wt.%, 0.005 wt.% - ensuring the required strength level of the steel.

Manganese is used, on the one hand, as a solid solution hardener, on the other hand, as an element of substantially increasing the stability of the supercooled austenite and increases the hardenability of steel. The upper levels of manganese (0.90 wt.%) is determined by the need to ensure the required level of ductility of steel, and the lower (0.30 wt.%) - the need to ensure the required level of strength and hardenability of the steel.

Silicon belongs to terrytoon anousim elements. The lower limit for silicon 0.01 wt.% caused by the deoxidation of steel. The silicon content above 0.15 wt.% will adversely affect the characteristics of ductility of steel.

Boron contributes to a sharp increase in the hardenability of steel. The upper limit of the boron content is determined by considerations of ductility of steel, and the lower the need to ensure the required level of hardenability.

Aluminum and titanium are used as deoxidizers and protect the boron from binding in the nitrides, which contributes to a sharp increase in the hardenability of steel. Thus, the lower level of the contents of these elements (0.02 and 0.01, respectively) is determined by the requirement to ensure the hardenability of steel, and the upper level (0.06 and 0.04) - requirement to provide a given level of ductility of steel.

Nitrogen, an element involved in the formation of carbonitrides, while lower levels (0.005 wt.%) is determined by the requirement to provide a given level of strength, and the upper level (0.015 wt.%) - the requirement to provide a given level of ductility and hardenability.

Calcium is an element, modifying nonmetallic inclusions. The upper limit, 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 with the questions of technological production is TBA.

Sulfur determines the level of ductility of steel. The upper limit is caused by the necessity of obtaining a given level of ductility and toughness of steel, and the lower limit issues-tech production.

To ensure complete bonding of nitrogen in the nitride type TiN and AlN as the result of reactions:

requires the following ratios of elements, otherwise protection boron from tying it in nitrides and decrease characteristics of the hardenability of steel.

Ratiodefines the conditions of preservation in more than 50% effective boron, which provides a set of characteristics of the hardenability of steel.

Ratioon the one hand, defines the conditions that ensure a given level of strength of the steel, on the other hand, determines the level of the base doping, providing a minimum level of hardenability of steel.

Ratioon the one hand, determines the conditions of providing a given level of viscosity steel as calcium modifies nonmetallic inclusions, on the other hand, determines the level of calcium, necessary for partial bonding of oxygen, freeing up extra is th number of aluminum and provides additional protection boron from binding in the nitrides.

Therefore, the claimed set of characteristics meets the criterion of "substantial differences".

Below is an example implementation of the present invention, not excluding other in the scope of the claims.

Melting boron steels produced in shaft furnace “Fuchs”. For guaranteed low nitrogen content developed special technology, including melt blending liquid cast iron up to 40% of the total volume of the mixture. Oxidative period provides a high rate of oxidation of carbon within 0,05-0,07%/min electric mode involves shutting off the furnace when the carbon content of 0.2-0.4 percent above the lower limit specified, dodavku the carbon produced without arcing. The temperature of the discharge from the furnace 1640-1680°C. Enter ferroalloys, steel treatment to remove non-metallic inclusions is made at the ladle furnace equipped with an electric heating system or hinotori. The temperature of the steel before casting on 60°C above the liquidus temperature of the brand. Casting is done in extended to the top of the mold. The mass of the ingot a 7.85 so To ensure a low content of nitrogen in the casting is the protection of the jet of metal with argon through a special ring device. Heating of the ingots in the blooming shop is regenerative wells until the temperature is s start rolling 1250-1270° C. Rolling of ingots produced at the blooming mill (mill 1300) and then on a continuous billet mill on the billet cross section of 100×100 mm For removing the formed during heating of ingots de-carbonized layer of the workpiece are subjected to abrasive blasting." Then he made hot rolling the resulting workpiece on a wire mill 150 or small-section mill 250 in diameters from 5.5 to 23 mm in coils. To ensure the value of de-carbonized layer is not more than 1% of the diameter of the limited rate of billets from the furnace is not less than 100 t/h for 150 mill and at least 56 t/h to 250 mill. The onset temperature rolling of billets 1220-1240° (C) to 250 mill and 1270-1290° (C) to 150 mill. Hot rolling of the rolled finish at a temperature of 1000-1050°With, then rapid cooling to 880-900°C, followed by cooling to 300°and then winding the coils.

In the hot rolling get rolled diameter of 12 mm with the structure of granular perlite (99%), bezplatny layer depth of 0.22 mm, score the actual grain - 9, cold sludge wire with a diameter of 12 mm at 90%, the temporary strength of 500 MPa, an elongation of 23%, reduced 75%.

Ratio

Ti=0,02%, N=0.007%, Al=0.03%

C=0,08%, Mn=0,60%

Ca=0,001%, S=0,008%

The introduction of the proposed product - rolled, round, boron steel of high hardenability provides obtaining directly into the mill stream (without additional spheroidizing annealing) patterns of rolled guaranteeing the rational conditions of cold massive forming geometrically-complex high-strength fasteners.

SOURCES of INFORMATION

1. EN 2177510 2, 21 D 8/06, 27.12.2001

2. SU 601321, With 22 38/12, 06.02.1976,

3. EN 2127769, WITH 22 38/14, 20.03.1999, (prototype)

Rolled, round, produced from micro steel containing carbon and alloying elements that have the specified quality parameters become non-metallic inclusions, structure, mechanical properties and hardenability and technology of plasticity, characterized in that the steel contains the following ratio of components, wt.%:

Carbon 0,06-0,11

Manganese 0,30-0,9

The silicon of 0.001 to 0.15

Bor 0,0005-0,0050

Vanadium is 0.005 to 0.08

Aluminum 0,02-0,06

Titanium 0.01 to 0.04)

Sera of 0,005 0,020

Nitrogen 0,005-0,015

Calcium 0,001-0,010

Iron and inevitable impurities Else

when performing ratios:

the maximum score of contamination of steel, non-metallic inclusions in sulphides, the 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 60% granular perlite, the amount of the actual grain 5-10 points, diameter from 10 to 16 mm, de-carbonized layer is not more than 1.0% of the diameter, the amount of cold upsetting of not less than 1/3 of the height, 50%of the hardenability of steel with a diameter up to 16 mm, ultimate strength, not more than 500 MPa, elongation not less than 22%, relative narrowing of at least 70%.



 

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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%.

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3 cl, 1 dwg, 1 tbl

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