A method of manufacturing rolled products of high-carbon steel

 

(57) Abstract:

Usage: the invention relates to ferrous metallurgy, in particular to a heat treatment of high carbon steel, and can be used in the manufacture of the cable rod and botofogo strips in the thread wire mills. Essence: the technology of the car, mostly rod and botofogo rolled high carbon steel, includes hot rolling, the shutter speed during 0,07-0,09 C, cooling at a rate above the critical up to 650-700oWith over 0.2 to 0.3 sec, exposure to air when the total time of the heat treatment roll after rolling to coiling in the bundles of 0.4-0.6, the winding in the coil and air cooling. The technical result of the invention is the possibility of obtaining high plastic characteristics on high-carbon steels at low dispersion properties over the cross section of the strand. table 2.

The invention relates to ferrous metallurgy, in particular to a heat treatment of high carbon steel, and can be used in the manufacture of the cable rod and botofogo strips in the thread wire mills.

Known methods of processing of wire rod and botofogo strips. For example, the known method obraschena stand of the mill for a time of 0.1-0.2 s to bulk temperature 770-850oC and air cooling /Auth. St. USSR 910804, MKI C 21 D 1/02, 8/06, publ. 07.03.82,/.

Closest to the claimed method according to the technical essence and achieved a positive result is a method of manufacturing heat-treated reinforcing steel in coils, including hot rolling, accelerated cooling from the mass-average velocity 1500-2500oC/s to a predetermined temperature, followed by exposure to air for 0.2-0.3 s, the winding in the coil while cooling each coil air / water mixture and the cooling /Auth. St. USSR 1770386, MKI C 21 D 1/02, 9/52, publ. 23.10.92,/.

The disadvantage of this method is the low level of regulated consumer properties and mechanical characteristics, such as relative narrowing, the value of de-carbonized layer, the dispersion of the structural components, the score of grain and microstructure in General. In addition, the use of known methods can not get a low mass scale on the surface of the rod.

The task of the invention is the possibility of obtaining high plastic characteristics on high-carbon steels at low dispersion properties over the cross section of the strand.

Supplies, including hot rolling, cooling at a rate above the critical to a predetermined temperature, exposure to air, the winding in the coil and cooling, according to the invention, after hot rolling, make the shutter speed during the time 0,07-0,09 C and cooling at a rate above the critical lead to temperatures of 650-700oC for a time of 0.2-0.3 s when the total time of the heat treatment roll after rolling to coiling in the bundles of 0.4-0.6 with.

It is found experimentally that for removal of the deformation stresses in the steel after rolling, you need to make the shutter speed of at least 0.07 s, at a speed of more than 0,09 with before cooling at a rate above the critical dramatically activates the process of scaling. To obtain uniform high dispersion patterns that satisfy the requirements of the cable rod class QC cooling needed to temperatures not higher than 700oWith in a period of time not less than 0.2 s, when cooled to temperatures below 650oWith the passage of time more than 0.3 for all cross-section rod is obtained, the structure of the school, which affects the ductility of the metal. When carrying out the heat treatment roll over time than 0.6 with before winding in the coil, Central heat treatment roll before winding in the coil is less than 0.4, with the value of de-carbonized layer above the standard requirements, in addition, increases the spread of properties across the section of the strand.

The proposed method of manufacturing rolled products of high-carbon steel with a specified set of, sequence of operations and the selection of intervals of the characteristic values in the specified range of their changes ensures the achievement of the technical result consists in providing better strength and plastic characteristics in high-carbon steels at lower values of de-carbonized layer and the amount of dross on the surface of the rod.

This technical result is achieved by solving the problem on inventive step, for example shutter speed between rolling and accelerated cooling, the choice of limits for the cooling and extracts, as well as temperature limits that should not be known prior art.

The implementation of the method of manufacturing rolled products of high-carbon steels was carried out as follows.

Example. In section rolling shop of JSC "ZSMK" in wire mill 250-1 conducted pilot testing of the proposed method in the manufacture of the cable wire rod with a diameter of 6.5 mm of steel 70 industrial melting.

For this loan after exposure to 0.08 with spent cooling speeds above the critical temperatures of 670oWith over 0,23 with, followed by exposure before winding in the coil within 0.15, while the total heat treatment time was 0.49, followed by a wire rod wound in a roll. Further cooling was carried out on the air.

The proposed method has been tested several modes, modifying the exposure time after rolling, cooling time, the total time of heat treatment, the temperature of the cooling in the claimed range of their changes beyond the boundary values. The modes of implementation of the proposed method are shown in table 1.

After the implementation of these modes were determined by tensile strength, a ten-fold elongation, relative narrowing, the value of de-carbonized layer and the amount of dross on the surface of the rod.

The results of industrial tests are shown in table 2.

From these tables it is seen that in the manufacture of the cable wire rod of high carbon steel in coils on the proposed method obtained the best results on plastic and strength characteristics of the metal (tensile strength - 920-940 N/mm2at tenfold relative elongation 13-16% and relative narrowing of 32-36%), while Kalim.

The proposed method is applicable to metallurgical enterprises with continuous rod mills and producing bortovoy car for various purposes. For example, the use of this method in the manufacture of the cable wire rod of high carbon steel in coils with wire mill JSC "ZSMK" showed high efficiency technology, as reflected in the act of industrial tests of the proposed method.

A method of manufacturing rolled products of carbon steel, mainly rod and botofogo rolled, including hot rolling, cooling at a rate above the critical to a predetermined temperature, exposure to air, the winding in the coil and the cooling air, wherein after hot rolling are doing endurance during 0,07-0,09 C and cooling at a rate above the critical lead up to 650-700oWith over 0.2 to 0.3 s when the total time of the heat treatment roll after rolling to coiling in the bundles of 0.4-0.6 C.

 

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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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