Method for the production of long-rolled products of 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 technical result of the invention to provide directly in the mill stream (without additional spheroidizing annealing) patterns of long steel products that provide sustainable conditions for cold massive forming geometrically-complex high-strength fasteners while providing increased performance hardenability of steel. To achieve a technical result smelted steel containing, in wt.%: carbon 0,17-0,32, manganese 0,90-1,40, silicon from 0.01 to 0.17, sulfur of 0,005 0,020, chrome 0,01-0,30, vanadium from 0.005 to 0.07, molybdenum from 0.005 to 0.10, Nickel from 0.005 to 0.10, niobium 0,005-0,02, titanium 0.01 to 0.04, boron 0,0005-0,0050, aluminum 0,02-0,06, nitrogen 0,005-0,015, iron rest. And: 12/S - Mn/0,055 20; 500(Ti/24-N/7)+0,20; -40 ° C/0,01+/0,00133, conduct secondary treatment, casting molds with stream protection, hot rolling of the ingot and receiving the workpiece and subsequent rolling, controlled cooling and winding rolled in the riots. Hot rolling finish when temperature is CLASS="ptx2">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.

Known structural steel, containing (wt.%): carbon 0.18-0.24%, manganese 0.90-1.30%, 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 of rolled steel from 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. 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 deformation is and receptions, used at various stages of steel making.

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), including heating to S, rolling in from 1150 to 800C order to obtain ferritic-pearlitic structure. Further heating 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 of high-strength fasteners, including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot and cooling (EN 2042734 C1, C 22 C 38/54, 27.08.1995 year).

The basis of the invention is the task of the development of steel of high hardenability and method of manufacturing it rolled, providing directly into the mill stream (without the exception is tructure rolled, ensuring rational conditions of cold massive forming geometrically-complex high-strength fasteners, as well as elevated values of characteristics of hardenability.

The technical result is achieved in that in the method of production of long-rolled products of boron steel for cold massive forming of high-strength fasteners, including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot and cooling, smelted steel in the following ratio, wt.%:

Carbon 0.17-0.32

Manganese 0.90-1.40

Silicon 0.01-0.17

Sulfur 0.005-0.020

Chrome 0.01-0.30

Vanadium 0.005-0.07

Molybdenum 0.005-0.10

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 inevitable impurities Else

When performing correlations:

hot finish rolling at a temperature of 1000-S and regulated cool, at first rapidly to a temperature of 880 to 900 ° C, and then air up to 300C.

Given the combination of alloying elements (p. 1) allow to get in the proposed steel (finished product di is not below market C) homogeneous fine structure of martensite leave with a favorable combination of strength and ductility.

Carbon and carbonitrides elements (vanadium, 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 and vanadium manage 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, affect the nature of --of transformation). Niobium and vanadium also contribute to the hardening of the steel during thermolysine. The upper limit of the content of carbon (0.32%), niobium (0.02%) and vanadium (0.07%) due to the need to ensure the required level of ductility of steel, and the bottom, respectively, 0.17%, 0.005% and 0.005% by providing the required strength level of the steel.

Manganese, molybdenum and chromium is used, on the one hand, as a solid solution hardener, on the other hand, as an element, substantially increasing the stability of the supercooled austenite and increases the hardenability of steel. The upper levels of manganese, - 1.40%, chromium (0.30%), molybdenum (0.10%) is determined by the need to ensure trebuetsa.pojilae steel.

Silicon belongs to territooriumil elements. The lower limit for silicon - 0.01% caused by the deoxidation of steel. The silicon content higher than 0.17% 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%) is determined by the requirement to provide a given level of strength, and the upper level (0.015%) - requirement to provide a given level of ductility and hardenability.

Nickel within the specified limits (0.005-0.10%) affects the characteristics of prokalivaemosti what Timothy obtain a given level of ductility and toughness of steel, and the lower limit (0.005%) - questions-tech production.

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

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

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.

Below is an example of the method.

Smelting boron steel containing carbon 0.29%, manganese 1.22%, silicon 0.17%, sulfur 0,010%, chromium 0.15% vanadium, 0.02%, molybdenum 0.009% Nickel and 0.04%, niobium 0.01%, titanium 0.03%, boron 0.0034%, aluminum 0.043%, nitrogen 0.010%, is produced in shaft furnace “Fuchs”. For guaranteed low nitrogen content developed special technology, comprising: melt blending a 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% of you who 1640-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 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 article the 880-900 ° C with subsequent cooling to 300C and the subsequent winding in the riots.

carbon 0.29%, manganese 1.22%,

titanium 0.03%, nitrogen 0.009%,

carbon 0.29%, boron 0.0044%.

The introduction of the proposed method of production of long-rolled products from boron steel of high hardenability, providing 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.

Method for the production of long-rolled products of boron steel for cold massive forming of high-strength fasteners, including steel smelting in the electric furnace, secondary treatment, casting molds, hot rolling of the ingot and cooling, characterized in that the smelted steel in the following ratio, wt.%:

Carbon 0,17-0,32

Manganese 0,90-1,40

Silicon, from 0.01 to 0.17

Sera of 0,005 0,020

Chrome 0,01-0,30

Vanadium from 0.005 to 0.07

Molybdenum from 0.005 to 0.10

Nickel from 0.005 to 0.10

Niobium 0,005-0,02

Titanium 0,01-0,04

Bor 0,0005-0,0050

Aluminum 0,02-0,06

Nitrogen 0,005-0,015

Iron Rest

when performing ratios 12/S-Mn/0,055 20; 500(Ti/24-N/7)+0,20, 40(C/0,01+/0,001)moslemism air cooling up to 300C.

 

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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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