Method of manufacturing hot-rolled sheet strip for pipe

 

(57) Abstract:

The invention relates to rolling production. The technical result improved quality of the finished products with high levels of uniform mechanical properties along the length of the strip by means of a homogeneous fine structure of the steel. The method includes heating the metal, rolling to obtain a strip thickness of 3.9 mm with regulation of temperature rolling, the total relative compression and rolling speed depending on the magnitude of carbon equivalent WITHe. Rolling in the finishing mill in the range of its temperature (t1-t2), where: t1= 638(Ce0,04+ 0,6),oC; t2= 0,9 t1at t1975oC; t2= 0,91 t1+ 15oWith t1= 980-995oC and t2= 0,93 t1+ 15oWith t11000oWith lead when the amount of the total relative compression19,35/(Ce+ 0,03), %. At temperatures less than t2but more than 700oWith the rolling is carried out at the total relative compression280/0,24, %, for Ce>0,29; %, Ce= 0,29-0,40;2200/0,6, %, for Ce= 0,41-0,46 and264,2/0,3, %, for Ce>0,46 with rolling rate of the value ofelead in two stages. Cooling the first stage in the interval (Tto-t), where Tto- temperature end of the rolling,oS; t = 586/(Ce+ 0,2)0,1,oWith lead with the cooling rate W10,1065(Tto/100)1,5, oC, for Ce0.32 and W10,0596(Tto/100)1,9,oC, for Ce0,33. Cooling the second stage is in the range of temperatures (t1'-t2'), where: t>t1'>t-(8-12oC) and t2' = 502/Se0,1,oWith lead with the cooling rate W20,058(Tto/100)1,7, oC, for Ce<0.26 and W2((Tto/100)/10 Ce+ 0,1) + (Tto/800) + 1,95,oC, for Ce0,26.

The invention relates to rolling production and can be used in the manufacture of hot-rolled sheet for pipe strip of carbon steel on broadband mills.

Hot-rolled strip steel in pipe strip of carbon steel with a carbon content of 0.06 to 0.60% of a thickness of 3.9 mm is used to produce welded pipes of various sizes, production technology which is described in the Handbook edited by C. I. and A. Zyuzin Century Tretyakov "rolling production Technology", vol. 2, M. : Metallurgy the cage. Mechanical properties and structure of the finished hot-rolled steel are determined by process parameters: the size of the total relative compression () in finishing mills, rolling speed (vCR), exposure of the metal prior to cooling, the temperature and cooling rate. These parameters are largely determined by the chemical composition of the steel, the observance of which determines the quality of the finished products.

A method of producing hot-rolled wide strips of high-carbon low-alloy steels, including hot rolling mill with temperature end of rolling 700-800oWith the cooling dushirovanie on the delivery table and the winding at a temperature of 500-600oWith rolling in the last two passes are performed with total compression 20-25% when the strip speed in the last passage of 5.0-7.5 m/s and the cooling of the band begin in 3-5 seconds after the end of the rolling speed of the cooling 9-15 degrees./with the support of the area dushirovaniya top and bottom strips in the ratio 1:(4-8) (A. C. the USSR 1196391, CL 21 D 8/02, publ. 07.12.85).

In the known method the value of the total relative compression and cooling rate of the metal are not regulated in Sauga rental for production, for example tubular strip thickness 4-16 mm, in particular the uniformity of the basic mechanical properties (tensile strengthinrelative elongation and value of impact toughness KCV) along the length of the strips.

The closest analogue of the claimed invention is a method of cooling the strips in the production of hot rolled strip steel on broadband continuous rolling mill 2000 (A. C. 1388438, CL 21 D 1/02, publ. 15.04.88). The known method includes heating the metal (slab) furnace up to 1270oWith, rolling to obtain a strip with a thickness of 5 mm with the temperature of the end of the rolling 850oAnd cooling with a regulated speed, due to the regulated flow of the refrigerant during cooling of the ends of the strip, which is determined depending on the value of the carbon equivalent and the temperature of the winding ratio

Fto= Fwith[(203-191)-(543-715)e-0,051 Sci],

where ftoFwithspecific fuel consumption for the end sections and the middle part of the strip, respectively, m3/m2h;

WITHecarbon equivalent;

Sci - temperature coiling,oC.

Signs nearest analogue, coinciding with the essential features of the claimed invention:

Denia with a regulated speed depending on the magnitude of carbon equivalent.

The known method cannot provide the required technical result for the following reasons.

Rolling strip in the known method is carried out at a temperature deformation mode, not regulated depending on the value of carbon equivalent, which does not provide a homogeneous fine structure, since each temperature corresponds to a certain critical degree of deformation necessary for complete recrystallization.

When rolling with elevated temperatures, there is the grain growth of austenite, which has a negative impact on the mechanical properties of the finished steel. Final structure of steel after rolling is a coarse-grained treatment of the mixture with inclusions of sections of the structure type of widmanstatten characterized by low viscosity, the correction of which requires additional heat treatment. The known method does not provide a high quality finished steel, because the mechanical properties are unevenly distributed along the length of the band and their level is low.

The basis of the invention the task is improving the production method is Noah steel structure provides a high level of uniform mechanical properties along the length of the strip, that allows you to improve the quality of the finished products.

The problem is solved in that in the method of production of hot-rolled sheet for pipe strip, comprising heating the metal, rolling the steel at a given temperature to obtain a strip thickness of 3.9 mm and cooling with a regulated speed depending on the magnitude of carbon equivalent WITHeaccording to the invention are rolling with the regulation of temperature rolling, the total of the reductions and the rolling speed depending on the magnitude of carbon equivalent, while rolling in the finishing mill in the range of rolling temperatures (t1-t2), where: t1= 638(Ce0,04+ 0,6),oC; t2= 0,9 t1at t1975oC; t2= 0,91 t1+ 15oWith t1= 980-995oC and t2= 0,93 t1+ 15oWith t11000oWith lead when the amount of the total relative compression19,35/(Ceto + 0.03)% and at a temperature less than t2but more than 700oWith the rolling is carried out at the total relative compression280/0,24, %, for Ce>0,29; %, Ce= 0,29-0,40;2200/0,6, %, for Ce= 0,41-0,46 and264,2/0,3, %, for Cmetroanime speeds are in two stages, while cooling the first stage in the interval (Tto-t), where Tto- temperature end of the rolling,oS; t = 586/(Ce+ 0,2)0,1,oC, lead with the cooling rate W10,1065(Tto/100)1,5, oC, for Ce0.32 and W10,0596(Tk/100)1,9,oC, for Ce0,33, and cooling the second phase in the temperature range (t1'-t2'), where t>t1'>t-(8-12oC) and t2' = 502/Ce0,1,oC, lead with the cooling rate W20,058(Tto/100)1,7, oC, for Ce<0.26 and W2((Tto/100)/10 Ce+0,1)+(Tto/800)+1,95,oC, for Ce0,26.

The mathematical dependences are obtained when processing the experimental data.

The value of carbon equivalent according to GOST 19281:

WITHe= + MP/6 + Si/24 + CR/5 + Ni/40 + Cu/13 + V/14 + R/2, where: S, MT, Si, Cr, Ni, si, V, P - content of chemical elements, %.

Lower limit of the thickness of the rolled strips (3.9 mm), the proposed method is selected in accordance with the gradation thickness of hot-rolled sheet according to GOST 19903. Mechanical properties of hot-rolled sheet and uniformity along its length depends on helices is ensuring a specified level and uniformity of mechanical properties. Since with increasing thickness of the strips mechanical properties are reduced, the proposed temperature-deformation mode when conducting regulated rolling in the finishing mills depending on the carbon equivalent provides the required level of mechanical properties for these steels when the thickness of the strip more than 3.9 mm

The essence of the proposed technical solution is in the regulation of the basic parameters of the production process of hot-rolled sheet for pipe strip thickness 3.9 mm with a carbon content in the steel 0,06-0,60%, which are selected depending on the value of carbon equivalent WITHefor a particular steel, which guarantees the highest quality in its properties of rolled products, and products made from it, for example, welded pipes has high consumer properties.

Regulation of temperature, rolling speed and the total relative compression depending on the carbon equivalent slows down the process of recrystallization in carbon steels. When this occurs, the elongation of austenitic grain, and with increasing degree of deformation uvelichivaetsya.poetomu crushed treatment patterns. Temperature-deformation mode rolling, corresponding to the claimed dependency leads to more complete use of the effect of static recrystallization in high-temperature phase, and the training structure of austenite to a phase transformation from a low number of structural imperfections after deformation.

When implementing the proposed method determines the value of Cerolled steel. Then determine the range of temperatures (t1-t2) rolling in the finishing mill and determines the required value of the total relative compression (1and2these stands at a regulated speed rolling (speed in separate cages increase, ranging from the rolling speed at the entrance to the finishing stand Vpcorrespondingly reducing the thickness of the strip). Then determine the intervals of temperatures (Tto-t) and (t1'-t2') and velocities of cooling metal W1and W2depending on theeon the first and second stages of cooling, followed by rolling of the proposed method.

For more effective grinding treatment of the grain changes the nature of the processes of strukturiert the phase of accelerated cooling after controlled rolling is largely determined by the capabilities of the braking processes of recrystallization of austenite, the intensity of which depends on the temperature defamation modes defined depending on the carbon equivalent, which enables to suppress the process of collective recrystallization. The second stage of the accelerated cooling is aimed at fixing a homogeneous fine structure in order to obtain a high level of uniform mechanical properties.

Example. Experimental validation of the proposed method was implemented on broadband with Tanah hot-rolling mill 2000 and 2500.

Rolling strips of different chemical composition and mix led to the regulation of process parameters: temperature rolling t1= f3(Ceand t2= f4(t1), the total relative compression1= f1(Se) and2= f2(AOC), the rolling speed Vp= f5(Ce), intervals of temperatures (Ttot) = f6(Ce) and (t1'-t2') = f7(Ceand cooling rates W = f8(TtoWITHe) at both stages. Temperature values t1, t2, t, t1', t2' ranged in 5oAnd the total of reductions was determined with an accuracy of 1%.

The rolling of a strip thickness of 6 mm oschino carbon equivalent was determined according to GOST 19281:e= + MP/6 + Si/24 + CR/5 + Ni/40 + Cu/13 + V/14 + R/2 = 0,19.

Rolling in the finishing mill stands were in the range of rolling temperatures t1= 638(Ce0,04+ 0,6) = 980oC and t2= 0,91 t1+ 15oC = 907oWhen the amount of the total relative compression (at a temperature of rolling 960oWith>t2): 19,35/Se+ 0,03 = 42,5% took1= 43%. The rolling speed at the entrance to the finishing stand was maintained equal to Vp= 0,65/Se+ 0,05 = 3.5 m/s is Obtained by rolling the strip is cooled in two stages water supplied through section dushiruumide device. Cooling the first stage in the temperature range (Tto-t), where Tto= 850oS; t = 586/(Ce+ 0,2)0,1= 644oWith, i.e., Tto-t = 850-644oWith led speed cooling W10,1065(Tto/100)1,5= 0,10658,51,5= 2.6 deg./C and cooling in the second stage in the temperature range (t1'-t2'), where: t>t1'>t-(8-12oS) = 644>t1'>634oWith, i.e., t1' = 640oC; t2' = 502/Se0,1= 593oC and t1'-t2' = 640-593oC were cooling rate W20,058(Tto/100)1,7= 0,0588,51,7= 2.2 deg./C. the cooling Rate was changed by including and Los 12 mm thickness of steel grade 45 the following chemical composition, %: C = 0,42; Mn = 0,54; Si = 0,24; Cr = 0,15; Ni = 0,12; Cu = 0,10; V-traces; P = 0.02.

WITHe= 0,42 + 0,54/6 + 0,24/24 + 0,15/5 + 0,12/40 + 0,10/13 + 0/14 + 0,02/2 = 0,57.

The parameters of the technological process:

t1= 638(0,570,04+ 0,6) = 1007oC;

t2= 0,931007 + 15oC = 952oWith, i.e., t1-t2= 1007-950oC.

Total relative compression at a temperature of 950o(I.e. less than t2but more than 700o(C) for Ce= 0,57 amounted to:19,35/(0,57 + 0,03) = 15,6%, took1= 16%. For Ce>0,46:228%; Vp= 0,65/0,57 + 0,05 = 1.2 m/s

Tto= 900oC; t = 586/(0,57 + 0,2)0,1= 602oWith, i.e., Tto-t = 900-602oC; 602>t1'>592oC, i.e., t1' = 600oC, t2' = 502/0,570,1= 531oC and t1'-t2' = 592-531oC.

Cooling rate:

W10,0596(900/100)1,9= 3.9 deg./(for Ce>0,33);

W24.6 deg./(for Ce>0,26).

The results of experimental rolling was estimated by laboratory tests on samples taken (after rolling and cooling of the metal from rolled strips. It was evaluated the microstructure of the steel and its dispersion and determined mechanical properties (inand KCV).

Most the m dependencies. When this dispersionindecreased by 22-30% in comparison with the properties of the strip, laminated by known techniques, taken as the closest analogue. The variance was reduced by 18-25%, and toughness (at -60oC, -20oAnd 20o(C) at 26-32%. The microstructure of samples was set to improve the kinetics of the decomposition of austenite in steel, with a resulting increase in its mechanical characteristics: greaterinon 10-17% with a slight decrease (i.e., the ductility of the metal is almost not deteriorated) and increase KCV by 9-18%.

Deviations from the proposed parameters led to deterioration of the mechanical properties of the finished steel. Lower temperatures1and t2(decreasing Vpand increase the total relative compression during rolling in the finishing mills deteriorates the mechanical properties of steel with a simultaneous decrease in KCV.

For conditions metallurgical plant improvement of consumer properties of carbon strip steel in pipe strip with a carbon content in the steel within 0,06-0,60% and a thickness of 3.9 mm will increase the price of its implementation by approximately 8%.

Method of manufacturing hot-rolled palauchenia strip thickness of 3.9 mm and cooling with a regulated speed depending on the magnitude of carbon equivalent WITHe, characterized in that the rolling is carried out with temperature regulation rolled, the total relative compression and rolling speed depending on the magnitude of carbon equivalent WITHewhile rolling in the finishing mill in the range of its temperature (t1-t2), where t1= 638(Ce0,04+0,6),oC; t2= 0,9 t1at t1975oC; t2= 0,91 t1+15oWith t1= 980-995oC and t2= 0,93 t1+15oWith t11000oWith lead when the amount of the total relative compression19,35/(Ce+0,03),% and at a temperature less than t2but more than 700oWith the rolling is carried out at the total relative compression280/0,24the % for Ce>0,29; % for Ce= 0,29-0,40;2200/0,6the % for Ce= 0,41-0,46 and 264,2/0,3the % for Ce>0,46 with the rolling speed at the entrance to the finishing stand Vp(0,65/Se) is+0.05, m/s, and cooling with regulated speeds are in two stages, with cooling in the first stage in the interval (Tto-t), where Tto- temperature end of the rolling,oS; t= 586/(Ce+0,2)0,1,oWith lead with the cooling rate W10,1065 (Tto/100)1,5,othe up - in the temperature range (t'1-t2'), where t>t'1>t-(8-12oC) and t'2= 502/Se0,1,oWith lead with the cooling rate W20,058 (Tto/100)1,7,oWith Ce>0.26 and W2((Tto/100)/10 Ce+0,1)+(Tto/800)+1,95, oWith Ce0,26.

 

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FIELD: rolling-mill machinery.

SUBSTANCE: the invention presents an installation for rolled metal cooling and is dealt with metal rolling, in particular with cooling of rolled metal. The installation for rolled metal cooling contains a body with an inlet branch-pipe and two rows of outlet branch-pipes displaced from each other by a half step. Value of a step of the outlet branch pipes in each row does not exceed four internal diameters of the branch-pipes. Across the body opposite to an entry of the inlet branch-pipe a dissector is installed. Along the body opposite to the outlet branch-pipes there are two entire central plates and two fragmentary lateral plates forming two longitudinal funnel-shaped cavities, turned by their narrow parts to each row of outlet branch-pipes. Fragmentariness of the lateral plates is created at the expense at least of one cutout in the base of each plate, at the longitudinal butts of which there are two perpendicularly fixed damping plates facing inside the funnel-shaped cavities. The invention allows to increase evenness, flexibility and efficiency of the rolling metal cooling process and ensures reliable operation of the installation.

EFFECT: the invention allows to increase evenness, flexibility and efficiency of the rolling metal cooling process and ensures reliable operation of the installation.

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