The production method of the rolled strip from sverhskorostey steel for subsequent stamping

 

(57) Abstract:

The invention relates to the field of metallurgy, in particular to the production of the rolled strip from sverhskorostey steel (IF-steel) for further forging used in the automotive industry. The production method of the rolled strip of low carbon steel for subsequent stamping includes a steel containing, in wt.%: carbon <0,01, silicon <0,01, manganese 0.1 to 0.15, sulfur <0,008, phosphorus <0,008, chrome <0,003, Nickel <0,003, copper <0,004, nitrogen <0,006, titanium 0,015-0,035, niobium 0,03 - 0,065, iron and inevitable impurities else, casting into slabs, heating the slab to a temperature of 1100-1200oWith, hot rolling temperature end of the rolling 890-910oWith the winding of the strips into rolls are at a temperature determined by the dependence of Tcm=-0,19 k2-0,013 k+729,95, where Tcm- temperature coiling,oC; k - coefficient characterizing the degree of stabilization of steel, equal to k=(Nb+l,9375(Ti-3,43 N-1.5 S)/C, where Nb, Ti, N, S, and s - content of niobium, titanium, nitrogen, sulfur and carbon in steel weight. %, the etching strips, cold rolling, continuous annealing and training with a compression of less than 1%. The proposed method provides a more uniform mechanical properties along the length of the strip and Ulu the production of the rolled strip from sverhskorostey steel (IF-steel) for further forging, used in the automotive industry.

A method of producing sheet metal for deep drawing, including steel containing, in weight. %: carbon 0,003, silicon 0.8, manganese 1, the phosphorus of 0.01, aluminum 0,01 - 0,1, nitrogen 0,008, iron rest, titanium and niobium in amounts determined by the ratio 48/14 [N (%) - 0,002%] <Ti (%) <4(%)+3,43 N(%) and 0.003% Nb(%)<0.25 per cent, so that Nb (%) >2C (%), and the total content of Nb and Ti in the steel was 0,04% (Application Japan 2 - 259023, CL 21 D 9/48, 8/04, With 22 38/00, 38/14, publ. 19.10.90). The steel is heated to 1000-1250oWith subsequent rough rolling, ending at a temperature of 950-1100oWith, and the finishing rolling, ending at a temperature 890-940oWith, and then hot-rolled strip steel wound into a roll with the subsequent processing to remove descaling and cold rolling and subjected to continuous annealing.

When the temperature of the end of the rolling - exceeding 920oC is the grain growth of ferrite. This adversely affects the formation of favorable texture { 111}, since it is known that shear deformation during cold rolling the emergence of favorable texture occurs at the boundaries of ferrite grains, the length of which during the grinding of the grain is reduced.

oWith, hot rolling temperature end of the rolling 890-910oWith the winding of the strips into rolls at a temperature of winding 600-740oWith the etching strips, cold rolling, continuous annealing and training with a compression of less than 1% (Jakubowski O. N. Particularly low carbon steel as the basis for the production of automobile body sheet. Production of rolled, 1999, 6, S. 37-42).

Signs nearest analogue, coinciding with the essential features of the invention: steel-with content <0.01% carbon with micro additives titanium and niobium, casting into slabs. heating the slab to a temperature of 1100-1200oWith, hot rolling temperature end of the rolling 890-910aboutWith the winding of the strips into rolls, etching strips, cold rolling, annealing and tempering with a compression of less than 1%.

In the known method does not carry out the regulation of the coiling temperature on the specific chemical composition of steel. The speed and completeness of sequestration of carbon in carbides and carbosulfan, in the process of cooling of the metal after hot rolling, depends mainly on the sewing process selection carbides and carbosulfan, but the rate of cooling of the outer and inner coils coils coils are substantially different. For example, during the winding of coils weighing 30 tons at a temperature of 740oWith the difference in the rate of cooling of the outer and inner turns of the roll in the first hours of cooling is 200-220oWith/hour.

Such a difference in the cooling rate of the various layers of the coil leads to the formation of a ferrite with different grain size and carbon content in the solid solution, which causes the formation of non-uniform properties along the length of the strip. Moreover, due to the complex influence of grain size of ferrite and carbon content in the solid solution on the formation of metal texture during cold rolling and annealing of this difference in the next stages of processing increases.

In addition, at high temperature coiling is the formation of hard grass of scale on the strip surface, which increases the time of etching and the deterioration of the surface of the strip.

Low temperature coiling (<670C) can lead to an increase of the yield strength and the appearance of the site fluidity. This is because some of the carbon may be in a solid solution, and not in the form of carbides or carbos what's temperatures, requires long annealing in bell-type furnaces, continuous annealing in units of continuous annealing (ANO) sverhskorostey steel coils at a given temperature, it is not possible to obtain a high complex properties of the finished products.

The basis of the invention the task is improving the production method of the rolled strip from sverhskorostey steel for further forging, in which due to the regulation of the coiling temperature on the specific chemical composition of steel, enhances the uniformity of mechanical properties along the length of the strip and improving the quality of its surface.

The problem is solved in that in the production method of the rolled strip from sverhskorostey steel for further forging, including steel content <0.01% carbon with micro additives titanium and niobium, casting into slabs, heating the slab to a temperature of 1100-1200oC, hot rolling temperature end of the rolling 890-910oWith the winding of the strips into rolls, etching strips, cold rolling, annealing and tempering with a compression of less than 1%, according to the invention the winding of the strips into rolls are at a temperature determined by the dependence of

Tcm=-0,19 k
< / BR>
where Nb, Ti, N, S, and s - content of niobium, titanium, nitrogen, sulfur and carbon in steel weight. %.

In a solid solution of low carbon steel contains a small amount of carbon and nitrogen, which are stabilized by the SIC and nitridebased elements such as titanium and niobium. Titanium is used for stabilization primarily of nitrogen, and then carbon and niobium for the stabilization of carbon.

First of all, this type of steel is stabilized nitrogen titanium, which begins in the melt. Stabilization of carbon begins at temperatures 930-1220oWith the conversion of sulfide titanium iS in complex carbosulfan Ti4C2S2and Ti3,2Ni0,8C2S2. The niobium carbide is allocated during and after the transformation, as exceeding the limit of solubility.

The speed and completeness of the stabilization of carbon in sverkhnizkochastotnye steels with additions of Ti and Nb depends mainly on the percentage of Nb, Ti, N, S and C in the steel. Steel containing titanium and niobium, sufficient for complete stabilization of nitrogen and carbon, or with excessive content can be cooled after hot rolling to lower the personal swimming trunks, can lead to essentially change the relationship microeconomic elements to N, C and S and, consequently, to influence the processes stabilize them.

Rolling ends in the austenitic region, when the process of stabilization of carbon is not fully completed. The coiling temperature is decisive as to obtain a solid solution, free from atoms implementation and, accordingly, low values of yield strength in the hot-rolled strip.

Winding the strips into rolls with the regulation of the temperature of the winding, depending on the specific chemical composition (degree of stabilization of carbon) steel ensures the receipt of finished steel with yield strengthof 0.2<175 MPa, tensile strengthin= 250-320 MPa, elongation >40% and a coefficient of normal plastic anisotropy rm> 2,2.

In addition, lowering the temperature of the winding leads to the increase of the share lightrange of vustite (FeO) in the slag, dross, which ensures the reduction of the time of etching and improving the quality of the strip surface.

Example.

In the basic oxygen furnace smelted steel of the following chemical composition, wt.%: 0,004; 0,01 Si; 0,15 Mn; 0,006 S; 0,008 P; 0,004 N; 0,oWith, were subjected to hot rolling temperature end of rolling TCP=910 - 920aboutC. the Winding of the strips into rolls were at a temperature determined by the dependence of

Tcm=-0,19 k2- 0,013 k + 729,95,

where Tcm- temperature coiling,oC.

k - coefficient characterizing the degree of stabilization of steel, equal

< / BR>
where Nb, Ti, N, S, and s - content of niobium, titanium, nitrogen, sulfur and carbon in steel, wt.%.

The coefficient k is equal to

< / BR>
The temperature of the winding is equal to

Tcm=-0,1916,032-0,01316,03+729,95oC = 681oWITH

After cooling rolls, the strip was subjected to etching in the unit of continuous etching (solution composition: 22% H2SO4, 8% FeSO4), cold rolling with a total degree of compression of 72%, the annealing in ANO and training with a degree of compression of 0.8%.

Ready strip has a conditional yield strength0.2= 168 MPa (yield stress is absent); tensile strengthin= 260-320 MPa; elongation = 40%; the ratio of the normal plane anisotropy rm> 2,0, resulting in the formation of categories hoods VOSV and VOSV-So

Lowering the temperature of the winding up to 681oC leads to a decrease in the difference in the speed of cooling the face of the properties along the length of the strip. The change in mechanical properties along the length of the strip is not more than 2%.

Lowering the temperature of the winding at 40 degrees (compared with the known method) significantly increases the etching capacity of the scale and quality of the strip surface. The surface of the strip after etching has no defects and is related to I and II groups of surface finish.

The production method of the rolled strip from sverhskorostey steel for further forging, including steel containing carbon <0.01 percent, sulfur, nitrogen, and microadditives of titanium and niobium, casting into slabs, heating the slab to a temperature of 1100-1200oWith, hot rolling temperature end of the rolling 890-910oWith the winding of the strips into rolls, etching strips, cold rolling, annealing and tempering with a compression of less than 1%, characterized in that the winding of the strips into rolls are at a temperature determined by the dependence of

Tcm= - 0,19 k2-0,013 k+729,95,

where Tcm- temperature coiling,oC;

k - coefficient characterizing the degree of stabilization of steel, equal

< / BR>
where Nb, Ti, N, S, and s - content of niobium, titanium, nitrogen, sulfur and carbon in the steel, wt. %.

 

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FIELD: metallurgy, production of rolled steel.

SUBSTANCE: the invention is pertaining to the field of metallurgy, production of rolled steel, in particular, to methods of production of cold rolled steel sheets with the high drawing properties for a cold forming of details of cars bodies. The technical problem being solved by the invention consists in improvement of the quality of a cold rolled sheet steel. The method provides for hot rolling of continuously-cast low-carbon steel slabs, etching treatment, multirun cold rolling with total relative reduction of no less than 75 %, a recrystallization annealing in the following mode: a heating at an average speed of 70-80°C/h up to temperature of 490-510°C, a repeated heating at an average speed of 3-4 °C/h up to the intermediate temperatures of 540-560 °C/h and the final heating at an average speed of 50 - 55°C/h up to the annealing temperature of 700-720 °C, at which the steel rolls are kept for 12-18 h. Upon termination of keeping the rolls at the annealing temperature they are cooled at the rate of 19-21 °C/h up to the temperatures not exceeding 690 °C. At that the continuously cast low-carbon steel slabs have the following chemical composition (in mass %): 0.025-0.050 - carbon, 0.003-0.010 - silicon, 0.12-0.19 - manganese, 0.02-0.05 - aluminum, no more than 0,011 - nitrogen, the rest - iron and impurities.

EFFECT: the invention ensures improvement of the quality of a cold rolled sheet steel.

3 cl, 5 ex, 3 tbl

FIELD: ferrous metallurgy; motor-car industry; production of steels intended for manufacture of items of a complex configuration with the help of cold sheet stamping.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy and motor-car industry, in particular, to methods of production of steels intended for manufacture by cold sheet stamping of items of a complex configuration, predominantly details for motor cars. The technical problem is to boost steel stamping, to improve the quality of a surface of a steel strip and hence to improve adhesion of a protective cover. The method includes a steel smelting, casting, hot rolling, strips reeling in rolls, a cold rolling, a recrystallization annealing and a temper rolling. The steel contains components in the following ratio (in mass %): Carbon - 0.002 - 0.008, silicon - 0.005-0.025, manganese - 0.05-0,20, phosphorus - 0.005-0.025, sulfur - 0.003-0.012, aluminum - 0.02-0.07, titanium - 0.02-0.05, niobium - 0.001 0.080, iron and imminent impurities - the rest. The hot rolling is completed at the temperature determined from the ratio: Tf.r≥ 7300 / (3.0-Ig [Nb] [C]) - 253, where Tf.r - temperature of the end of the rolling, °C; [Nb] and [C] - the shares of niobium and carbon in the steel accordingly in mass %, and the recrystallization annealing is carried out in a pusher-type furnace at the temperature assigned depending on the contents of niobium in steel according to the equation: Tan= (750+ 1850 [Nb]) ± 20, where Tan - a temperature of the thermal treatment, °C; [Nb] - the contents of niobium in the steel, in mass %.

EFFECT: the invention allows to boost the steel stamping, to improve the quality of the steel strip surface and adhesion of a protective cover.

4 ex, 1 tbl

FIELD: metallurgy; methods of production of thin-sheet hot-rolled steel.

SUBSTANCE: the invention is pertaining to the field of rolling, in particular, to methods of production of thin-sheet hot-rolled steel. The technical result of the invention is production of hot-rolled steel of no more than 3.9 mm thick with the properties similar to the properties of the cold- rolled sheet steel, and having a tarnish or a rough surface, that increases commercial profits of the rolled steel. The offered method provides for hot rolling of bands, their refrigerating to the temperature of a reeling - tc by the sectional water quenching, a reeling, etching treatment with HCI solution and a temper rolling. For the bands of steel with a carbon share of up to 0.1 mass % the temperature of the end of rolling is kept equal to 860... 890°C. The water quenching of the bands begin in 7...9 seconds after the end of rolling, and tc is taken within the temperatures range of 640... 700°ะก. At that the bands temper rolling for production of their tarnish surface realize in the rollers with a height of micro-asperities of the barrels Ra = 2.2... 2.7 microns and for production of the rough surface - with = 2.9... 4.0 microns.

EFFECT: higher efficiency.

1 ex

FIELD: metallurgy; methods of production of steels with homogeneous properties.

SUBSTANCE: the invention is pertaining to the field of metallurgy, in particular, to production of deep-drawing steels used for production of items of the complex configuration, predominantly - he details of motor-cars. The technical result of the invention is increased homogeneity of mechanical properties of the steel and reduction of cost of its production. This technical result is achieved due to the fact, that they conduct a continuous casting of the steel containing of no more than 0.007 mass % of carbon and 0.006 mass % of nitrogen in slabs, heating and hot rolling in bands, refrigeration, a reeling in rollers, etching, cold rolling with compaction of no less than 70 %, annealing and temper rolling. The annealing of cold-rolled steel conduct in the pusher-type furnace at temperatures of 750 ÷ 900°C during 5 ÷ 18 minutes.

EFFECT: the invention ensures increased homogeneity of mechanical properties of the steel and reduction of cost of its production.

2 tbl 1 ex

FIELD: ferrous metallurgy; methods of a steel production.

SUBSTANCE: the invention is pertaining to ferrous metallurgy, in particular, to the methods of production of steel for a deep drawing applied at production of items of a complex configuration, predominantly details of cars. The technical result of the invention is an increase of homogeneity of its mechanical properties and reduction of expenditure for its production. The technical result is reached by conducting a continuous casting of the steel containing of no more than 0.007 mass % of carbon and 0.006 mass % of nitrogen in slabs, their heating at the temperatures of 1000÷1160°C and their hot rolling in bands with the temperature of the end of rolling equal to 620 ÷ 720°C, chilling of bands by a still air and their reeling in rolls at temperatures of 600 ÷ 680°C, etching treatment, cold rolling with cold reduction by not less than 70 %, an annealing at temperatures of 650 ÷ 900°C and temper rolling. Aging of the cold-rolled steel at annealing conduct during 5÷18 minutes at temperatures of 750÷ 900°C in pusher-type furnaces, and aging for 11÷34 hours - at temperatures of 650÷ 750°C in the bell-type furnaces.

EFFECT: the invention ensures increased homogeneity of the steel mechanical properties and reduction of expenditure for its production.

2 cl, 1 dwg, 2 tbl, 1 ex

FIELD: black metallurgy.

SUBSTANCE: method includes hot rolling, cooling down to winding temperature, winding of bar in a roll, heating bar up to zinc-plating temperature and applying of zinc plating, cooling of bar is performed after black group of cages with speed 0,3-0,6°C/c, and after white - with speed 20-30°C/c with point of start of process in 2,5-3,0 after exit of bar from last cage of white group.

EFFECT: higher efficiency.

1 tbl, 5 ex

FIELD: ferrous metallurgy; methods of production of the steel strips.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, to the method of production of the steel strips from the low-carbon automobile-body sheet steel. The technical result of the invention is the increased output the steel strips: the rather special complex ironing (RSCI), the special complex ironing (SCI), the complex ironing (CI) and ensuring achievement of the required level of the physical-mechanical properties of the steel strips. The technical problem has been solved in three versions. The steel strip is produced by the hot rolling, the subsequent cold rolling, the reeling of the cold-rolled strips in the rolls and their annealing in the bell-type furnaces with the heating up to the temperatures of the recrystallization annealing belowACl : 650-720°C. The RSCI rolls heating exercise in four stages: on the first stage - up to 320-600°C with the rate of 60-270°C/h, on the second stage - up to 360-630°C with the rate of 10-30°C/h, on the third stage - up to 400-649°C with the rate of 5-7°C/h, on the fourth stage - up to 650-720°C with rate of 8-70°C/h. In the second version SCI rolls are heated up in three stages: on the first stage - up to 320-600°C with the rate of 60-270°C/h, on the second stage - up to 360-649°C with the rate of 10-30°C/h, on the third stage - up to 650-720°C with the rate of 8-70°C/h. In the third version the CI rolls are heated up to 650-720°C in two stages: on the first stage - up to 320-649°C with the rate of 60-270°C/h, on the second stage - up to 650-720°C with the rate of 8-70°C/h.

EFFECT: the invention ensures the achievement of the required level of the physical-mechanical properties of the steel strips.

3 cl, 3 tbl, 5 ex

FIELD: metallurgy, namely processes for cold rolling steel sheets with high drawing properties, possibly used for cold forming of body parts of passenger cars.

SUBSTANCE: method is realized at keeping temperature values of rolling termination and coiling in ranges 850 - 910°C and 540 - 730°C respectively. Cold rolling is performed at total reduction 65 - 88%. Annealing stage is performed at heating up to temperature 700 -750°C and soaking at such temperature for 10 - 25 h. Steel for making cold rolled sheets contains next ingredients, mass %: carbon, 0.001 - 0.006; silicon, 0.005 - 0.04; manganese, O.05 - 0.25; aluminum, 0.01 - 0.08; titanium, 0.01 - 0.09; niobium, no more than 0.05; boron, no more than 0.001; chrome, no more than 0.06; nickel, no more than 0.06; copper, no more than 0.06; sulfur, no more than 0.012; phosphorus, no more than 0.10; nitrogen, no more than 0.006; iron, the balance. If niobium is absent and relation Ti/(4C + 3.43N + 1.5S)≥ 1 is satisfied, reduction degree at skin pass rolling is set in range 0.20 - 0.60% and if given relation is less than 1 it is set in range 0.61 - 1.2%. If niobium is present and next relations of chemical elements content in steel Ti/3.43N ≥ 1 and Nb/7.75C ≥ 1 are satisfied, reduction degree at skin pass rolling is set in range 0.20 - 0.60% and if given relations are less than 1 it is set in range 0.61 - 1.2%.

EFFECT: less loss of yield, improved drawing capability of steel sheets.

7 cl, 3 tbl, 1 ex

FIELD: metallurgy; heat treatment of materials.

SUBSTANCE: proposed method consists in heating the roll at temperature interval of 200-570°C at rate of 80-90°C/h followed by heating to temperature of 640-660°C at rate of 20-30°C and heating at rate of 20-25°C/h to annealing point. Besides that, holding at annealing temperature is set according to the following relationship: τ=(0.8-0.9)M, where τ is holding time, h; M is mass of lower roll in stack, t.

EFFECT: reduced duration of annealing at high mechanical properties and improved quality of cold-strip surfaces.

2 cl, 3 tbl, 1 ex

FIELD: ferrous metallurgy, namely cold sheet forming, particularly motor vehicle parts.

SUBSTANCE: method comprises steps of melting steel, casting it, hot rolling in rough and finish stand group of continuous wide rolling mill, coiling strip, cold rolling, subjecting it to recrystallization annealing in hood furnace at temperature no less than 690°C and skin pass rolling of strip. Melt steel contains, mass %: carbon, 0.01 -0.06; silicon, 0.003 - 0.030; manganese, 0.05 - 0.25; phosphorus, 0.003 - 0.020; sulfur, 0.002 - 0.023; acid soluble aluminum, 0.01 - 0.06; nitrogen, 0.002 -0.007; iron and inevitable impurities, the balance while satisfying next relations: [Mn]x{S]≤ 0.045 and 5 ≤ [Al}/[N]≤ 20. Hot rolling in rough stand group is ended when thickness of rolled piece is 35 mm and more at temperature Tp ≥ 1050 + 8000[Mn][S]. Heating at recrystallization annealing is realized at first up to 450 - 500°C for time period no more than 10 h. After temperature 450 - 500°C is achieved heating is realized at rate no more than 20°C/h at least till 550 - 600°C and then at rate no more than 50°C/h till annealing temperature.

EFFECT: improved formability of steel at keeping its surface quality.

1 tbl, 5 ex

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