Method of manufacturing spheroidizing rolled from boron steel for cold massive forming of high-strength fasteners

 

(57) Abstract:

The invention relates to the field of metallurgy, in particular to the production of long-rolled products of boron steel for cold massive forming of high-strength fasteners particularly complex form. The task of the invention to provide patterns of long steel products that provide sustainable conditions for cold massive forming geometrically-complex high-strength fasteners. The technical result consists in the simultaneous provision of high characteristics of the hardenability of steel. To achieve a technical result carry out smelting of steel in electric furnaces, secondary treatment, casting molds with stream protection, hot rolling of the ingot and receiving the workpiece and subsequent controlled rolling, winding rolled in coils, cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing, including high-speed induction in microtechno temperature range of cold metal followed by controlled cooling in the temperature range 650-S, with speeds of 0.5-1.0 C/min, and further cooled in a heat chamber at 100-200C. Smelted steel, with components, wt.%: carbon 0,17-0,26, manganese 0,90-1,30, silicon 0,01-0,20, chrome from 0.005 to 0.35, boron 0,0005-0,0050, niobium 0,001-0,02, aluminum 0,02-0,06, titanium 0.01 to 0.04, nitrogen 0,005-0,015. Moreover: N/(10Ti+Al)0,039; (10V-0.01)/N1,80. Microalloying of steel niobium inhibits the processes of recristallization steel at a temperature of finish rolling 950-1000C, which allows to realize the technology of controlled rolling on the existing equipment and provides for the formation of fine patterns.

The invention relates to the field of metallurgy, in particular to the production of long-rolled products of boron steel for cold massive forming of high-strength fasteners particularly complex form.

The task of the invention to provide patterns of long steel products that provide sustainable conditions for cold massive forming geometrically-complex high-strength fasteners. The technical result consists in the simultaneous provision of high characteristics of the hardenability of steel.

Known structural steel containing, wt.%: carbon 0,18-0,24%, manganese 0,90-130%, silicon 0,17-0,37%, boron 0.0005-0.0050%, nitrogen 0.005-0.015%, vanadium of 0.01 to 0.08%, titanium 0.01 to 0.04%, the rest of the iron in the following ratio, wt.%: (patent of the Russian Federation).

The most important requirement is s 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. This steel from blending until ready rolled it takes a long processing, comprising the following operations: smelting, hot rolling, spheroidizing annealing, calibration. The task of providing the necessary mechanical properties and performance of technological plasticity and low coefficient of strain hardening of the metal in the state of delivery currently successfully resolved through a number of techniques used at different stages of production are:

Known production method (JP Patent 61-163210, 23.07.1986, With 21 D 8/06), including heating rods to 950º C, which ensures the selection of the nitrides of aluminum and boron, followed by cooling with water at a rate of 25/min to room temperature. This method will not provide the required level of spheroidizing patterns used class of steel.

A known method for the production of bar reinforcement (Patent DE 3434744 A1, 03.04.1986, With 21 D 8/06), the EV to 1000C and then cooled to room temperature.

The closest analogue is a method for the production of long-rolled products of boron steel for cold massive forming, high strength fasteners, including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot and cooling (EN 2042734 C1, With 22 38/54, 27.08.1995 year).

The task of the invention to provide patterns of long steel products that provide sustainable conditions for cold massive forming geometrically-complex high-strength fasteners. The technical result consists in the simultaneous provision of high characteristics of the hardenability of steel.

To achieve a technical result, in the method of production of long steel products, including steel smelting in the electric furnace, the production of metal, secondary treatment, casting molds, hot rolling the ingot to receive the workpiece and the cooling of the cast steel in the following ratio, wt.%:

Manganese 0,90-1,30

Silicon 0,01-0,20

Chrome 0,005-0,35

Bor 0,0005-0,0050

Niobium 0,001-0,02

Titanium 0,01-0,04

Nitrogen 0,005-0,015

Iron and

inevitable impurities Else

when performing ratio N/10Ti+Al0,039; 10B of 0.01 C/N1,80 the cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing by high-speed heating of cold-deformed rental in microtechno range of temperatures and followed by controlled cooling in the temperature range of 730-650C at a rate of 0.5 to 1.0 C/min, and further cooling in a heat chamber at room temperature 100-200C to reduce the duration of the process of spheroidizing.

And

Given the combination of alloying elements (p. 1) allow to get in the proposed steel (finished product diameter up to 25 mm), after thermolysine (quenching from a temperature of at least S with subsequent tempering temperature not lower than C) homogeneous fine structure of martensite leave with a favorable combination of strength and ductility.

Carbon and carbonitrides elements (niobium) are entered 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 niobium manages the processes in the austenitic region (determines the tendency to grain growth of austenite, stabilizes the structure during thermomechanical processing, increases the temperature of recrystallization and, consequently, affects the character --transformation. Niobium also contributes to hardening of the steel during thermolysine. The upper limit of carbon content (0,26%), niobium (0,02%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively 0,17%, 0.005% and provide the required strength level of the steel.

Manganese and chromium IP is exceeding the stability of the supercooled austenite and increases the hardenability of steel. The upper levels of manganese - 1,30% and chromium - 0,35% determined by the need to ensure the required level of ductility of steel, and the lower - 0.90% and 0.005%, respectively, of the need to ensure the required level of strength and hardenability of the steel.

Silicon belongs to territooriumil elements. The lower limit on the silicon of 0.01% is caused by the deoxidation of steel. The silicon content higher than 0,20% 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. So 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 of 0.06 and 0.04) requirement provide a given level of ductility of steel.

Nitrogen, an element involved in the formation of carbonitrides, the lower the level of its claim to provide a given level of ductility and hardenability.

To ensure complete bonding of nitrogen in the nitride type TiN and A1N result of reactions

[Ti]+[N]=TiN [Al]+[N]=A1N

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

Ratios

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

An example of the method.

Smelting boron steel containing carbon of 0.23%, manganese of 1.25%, silicon 0.15 percent chromium and 0.15%, boron 0,0023%, niobium 0,01%, aluminum 0,044%, titanium 0,028%, nitrogen 0,009% 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-C. Enter ferroalloys processing is antropologia or hinotori. The temperature of the steel before casting on 60 DEGREES above the liquidus temperature of the brand. Casting is done in extended upward moulds. 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 before the temperature started rolling 1250-S. Rolling ingots produced at the blooming mill (mill 1300) and then on a continuous billet mill on the billet cross section 100100 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-S for mill 250 and 1270-S for 150 mill. Hot rolling of the rolled finish at a temperature of 1000-S, then rapid cooling to 950-1000C and wind up in the riots. Followed by etching gorjachekatannoj podmazochnaja coverage. Followed by cold deformation calibration with deformation of 20-25% and spheroidizing annealing, including high-speed induction in microtechno temperature range (ACl+10-30C) of cold metal followed by controlled cooling in the temperature range 650-S, with speeds of 0.5-1.0 C/min, and further cooled in a heat chamber at ambient temperature 100-200S, which reduces the duration of the process of spheroidizing 5-10 times

nitrogen 0,009%, aluminum 0,044%, titanium 0,028%,

carbon 0,23%, boron 0,0023%, nitrogen 0,009%.

The introduction of the proposed method of production of long-rolled products from boron steel of high hardenability, providing spheroidizing patterns rolled guaranteeing the rational conditions of cold massive forming geometrically-complex high-strength fasteners.

Method of manufacturing spheroidizing rolled from boron steel for cold massive forming of high-strength fasteners, including steel smelting in the electric furnace, the production of metal, secondary treatment, casting molds, hot rolling the ingot to receive the workpiece and cooling, otlichayushiesya 0,90-1,30

Silicon 0,01-0,20

Chrome 0,005-0,35

Bor 0,0005-0,0050

Niobium 0,001-0,02

Aluminum 0,02-0,06

Titanium 0,01-0,04

Nitrogen 0,005-0,015

Iron Rest

when performing ratio N/(l0Ti+Al)0,039; (10B-C 0,01)/N1,80, where N is nitrogen, Ti - ti, Al - aluminum, boron, carbon, hot finish rolling at 950-1000C, then spend the cold deformation calibration with deformation rate of 20-25% and spheroidizing annealing by high-speed heating of cold-deformed rental in microtechno range of temperatures and followed by controlled cooling in the temperature range of 730-650C at a rate of 0.5 to 1.0 C/min, and further cooling in a heat chamber at room temperature 100-200C to reduce the duration of the process of spheroidizing.

 

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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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