CN108546881A - A kind of preparation method of no yield point elongation cold rolling medium managese steel strip - Google Patents

Abstract

The invention belongs to the technical field of iron and steel alloy materials, and in particular relates to a method for preparing a non-yielding platform cold-rolled medium manganese steel thin strip. The technical scheme of the present invention is as follows: a method for preparing a non-yielding platform cold-rolled medium manganese steel thin strip, comprising the following steps: (1) melting molten steel; (2) pouring into a tundish; (3) pouring into a cloth ladle; (4) Casting and rolling with twin-roll thin strip continuous casting equipment; (5) Cast strips are hot-rolled once, air-cooled and then curled; (6) Hot-rolled coils are annealed in reverse phase change; (7) Cold-rolled after pickling; (8) ) Reverse phase transformation annealing of cold-rolled sheet. The method for preparing the cold-rolled medium manganese steel thin strip on the non-yield platform provided by the present invention prepares the cold-rolled medium manganese steel thin strip on the non-yield platform to solve the problem that Lüders bands are easy to appear in the deformation of the cold-rolled medium manganese steel and cause obvious defects in the finished plate. Wrinkle phenomenon, and solve the problems of long conventional production process, high cost and high energy consumption of cold-rolled medium manganese steel.

Description

A kind of preparation method of non-yielding platform cold-rolled medium manganese steel thin strip

technical field

The invention belongs to the technical field of iron and steel alloy materials, and in particular relates to a method for preparing a non-yielding platform cold-rolled medium manganese steel thin strip.

Background technique

Energy saving and emission reduction, reducing vehicle weight and improving vehicle collision safety are the main goals of the development of the automobile industry at present, and the development of high-strength steel for automobiles has become an important development trend. Advanced high-strength steel has excellent strength and plasticity matching (that is, strong plastic product), which can ensure the safety performance of automobile collision while reducing the weight of automobiles. The strength-plastic product of the first generation of advanced high-strength steel is low (≤25GPa%), mainly including steel types such as dual-phase steel, interstitial-free steel and phase transformation induced plasticity steel; the second-generation advanced high-strength steel has higher strength-plasticity Area (40 ~ 70GPa%), mainly including high manganese steel. Due to the addition of more alloying elements, such as manganese, to the second-generation advanced high-strength steel, the production cost is higher. Therefore, it is urgent to develop the third-generation advanced high-strength steel. At present, medium manganese steel is considered to be a third-generation advanced high-strength steel with great potential. The mass fraction of manganese in medium manganese steel ranges from 3% to 12%, and ferrite and austenite structures can be obtained through reverse phase transformation annealing process. The austenite content in the medium manganese steel ranges from 20% to 60%, and the medium manganese steel has a relatively high strength-plasticity product (25-60GPa%).

However, it is currently found that the cold-rolled medium manganese steel will have a relatively long Lüders band phenomenon during the stretching process, and the Lüders band will reduce the surface quality of the medium manganese steel plate during the processing and forming process, resulting in obvious cracks in the finished plate. The wrinkle phenomenon affects the use of users. Therefore, this problem has become an obstacle to the application of cold-rolled medium-manganese steel. It is urgent to develop cold-rolled medium-manganese steel products without yield platform. In addition, the current conventional production process of cold-rolled medium-manganese steel is relatively long. After smelting and continuous casting, high-temperature homogenization of the billet is required. Usually, it needs to be heated to 1200-1250°C for a long time, and then rough rolling and finishing are carried out. Rolling process to obtain hot-rolled sheets, followed by pickling, cold rolling and annealing processes. This conventional production process not only consumes a lot of energy, but also has a long production process and relatively high preparation costs.

Contents of the invention

The invention provides a method for preparing a non-yielding platform cold-rolled medium manganese steel strip, and prepares a non-yielding platform cold-rolled medium manganese steel strip to solve the problem that the cold-rolled medium manganese steel deformation is prone to appear Lüders bands and cause obvious appearance of finished plates The problem of wrinkling phenomenon, and solve the problems of long conventional production process, high cost and large energy consumption of cold-rolled medium manganese steel.

Technical scheme of the present invention is as follows:

A method for preparing a non-yielding platform cold-rolled medium manganese steel thin strip, comprising the steps of:

(1) Smelting molten steel, the components of molten steel are: C 0.1~0.4%, Mn3~10%, Si<2%, Al<3%, S<0.002%, P<0.002%, O<0.002%, N <0.003%, the balance is Fe;

(2) The molten steel is then poured into the tundish, then poured from the tundish into the cloth flow ladle, and finally poured from the cloth flow ladle into the twin-roll strip continuous casting equipment, and the thickness is 1.5-3.0mm obtained by casting and rolling cast belt;

(3) After the cast strip is cooled to the starting rolling temperature, hot rolling is carried out one time. The starting rolling temperature is 1000-1250°C, the total reduction of hot rolling is 10%-30%, and the final rolling temperature is 900-1150°C. After rolling, it is air-cooled to 300-500°C for crimping to obtain a hot-rolled sheet;

(4) Heating the hot-rolled sheet to 600-800° C. for 30 minutes to 8 hours to complete the reverse phase change annealing to obtain a reverse-phase-change annealed hot-rolled sheet;

(5) Pickling the hot-rolled sheet annealed by reverse phase change annealing to remove scale, and then cold-rolling, the total reduction of cold-rolling is 10-27%, to obtain a cold-rolled sheet;

(6) Heat the cold-rolled sheet to 600-800°C for 1min-12min, complete reverse phase transition annealing, and then air-cool to room temperature to obtain a non-yielding platform cold-rolled medium manganese steel strip with a thickness of 0.75-1.9mm.

The preferred solution of the method for preparing the non-yielding plateau cold-rolled medium manganese steel thin strip is that the reverse phase transformation annealing time of the cold-rolled plate is 1 minute to 12 minutes.

The preparation method of the non-yield platform cold-rolled medium manganese steel thin strip, the preferred solution is that the microstructure of the non-yield platform cold-rolled medium manganese steel strip includes lath ferrite and lath austenite .

The preparation method of the non-yield platform cold-rolled medium manganese steel strip, its preferred scheme is that the engineering stress-strain curve of the non-yield platform cold-rolled medium manganese steel strip has the characteristics of continuous yield, and its tensile strength It is 700~1400MPa, and the elongation after breaking is 20~60%.

The beneficial effects of the present invention are: the preparation process of the non-yielding platform cold-rolled medium manganese steel thin strip of the present invention utilizes the twin-roll thin strip continuous casting technology, and the molten steel is directly cast and rolled into a cast strip with a thickness of 1.5-3.0mm, saving The continuous casting machine, slab heating furnace, rough rolling and finishing rolling units and other production equipment of the traditional strip steel production process are removed, and the entire production process of the strip steel is significantly shortened. Therefore, production energy consumption and production costs can be effectively reduced.

Detailed ways

In the specific implementation process, the molten steel of the present invention is poured from the ladle into the twin-roll strip continuous casting equipment. A molten pool is formed in the cavity, and the molten steel is solidified and exported through the gap of the casting rolls.

The standard used in the testing of tensile strength and elongation after break in the embodiment of the present invention is GB/T228.1-2010, the gauge length of the tensile sample is 25mm, tested at room temperature, and the tensile rate is 2mm/min.

Example 1

Melting molten steel, its composition is to contain C 0.23%, Mn 4%, Si 0.5%, Al 2%, S0.001%, P 0.0012%, O 0.002%, N 0.001% by mass percentage, and the balance is Fe; Molten steel is poured into the tundish, then poured from the tundish into the cloth flow ladle, and finally poured from the cloth flow ladle into the twin-roll thin strip continuous casting equipment, and cast and rolled to obtain a cast strip with a thickness of 2.0mm;

After the cast strip is cooled to the starting rolling temperature, hot rolling is carried out one time. The starting rolling temperature is 1250°C, the total reduction of hot rolling is 20%, and the final rolling temperature is 1150°C. After hot rolling, it is air cooled to 400°C for crimping, and hot rolled plate;

Heat the hot-rolled sheet to 700°C for 60 minutes to complete reverse phase transition annealing to obtain a reverse phase transition annealed hot-rolled sheet;

Pickling the hot-rolled sheet annealed by reverse phase change annealing to remove scale, and then performing cold rolling with a total reduction of 20% to obtain a cold-rolled sheet;

Heat the cold-rolled sheet to 700°C for 5 minutes, complete reverse phase transition annealing, and then air-cool to room temperature to obtain a non-yielding platform cold-rolled medium manganese steel thin strip with a thickness of 1.28mm, a tensile strength of 1050MPa, and an elongation after fracture of 48%, the structure is composed of lath ferrite and lath austenite structure.

Example 2

Melting molten steel, its composition is to contain C 0.1%, Mn 10%, Si 0.5%, Al 1%, S0.002%, P 0.002%, O 0.001%, N 0.003% by mass percentage, and the balance is Fe; Molten steel is poured into the tundish, then poured from the tundish into the cloth flow ladle, and finally poured from the cloth flow ladle into the twin-roll thin strip continuous casting equipment, and cast and rolled to obtain a cast strip with a thickness of 3.0mm;

After the cast strip is cooled to the starting rolling temperature, hot rolling is carried out one time. The starting rolling temperature is 1120°C, the total hot rolling reduction is 30%, the finishing rolling temperature is 900°C, and after hot rolling, it is air-cooled to 500°C for crimping, and hot rolled plate;

Heat the hot-rolled sheet to 600°C for 8 hours to complete the reverse phase transition annealing, and obtain the reverse phase transition annealed hot-rolled sheet;

Pickling the hot-rolled sheet annealed by reverse phase change annealing to remove scale, and then cold-rolling, the total reduction of cold-rolling is 10%, to obtain a cold-rolled sheet;

Heat the cold-rolled sheet to 600°C for 12 minutes, complete reverse phase transition annealing, and then air-cool to room temperature to obtain a flat cold-rolled medium manganese steel strip without yield. The thickness is 1.9mm, the tensile strength is 1400MPa, and the elongation after fracture is 20%, the organization is composed of lath ferrite and lath austenite structure.

Example 3

Melting molten steel, its composition is to contain C 0.2%, Mn 3%, Si 1%, Al 1%, S0.001%, P 0.0013%, O 0.0012%, N 0.001% by mass percentage, and the balance is Fe; Molten steel is poured into the tundish, then poured from the tundish into the cloth flow ladle, and finally poured from the cloth flow ladle into the twin-roll thin strip continuous casting equipment, and cast and rolled to obtain a cast strip with a thickness of 1.5mm;

After the cast strip is cooled to the starting rolling temperature, hot rolling is carried out in one pass. The starting rolling temperature is 1000°C, the total reduction of hot rolling is 30%, and the final rolling temperature is 920°C. After hot rolling, it is air cooled to 300°C for crimping, and hot rolled plate;

Heat the hot-rolled sheet to 800°C for 30 minutes to complete the reverse phase change annealing, and obtain the hot-rolled sheet reversed phase change annealed;

Pickling the hot-rolled sheet annealed by reverse phase change annealing to remove scale, and then cold-rolling, the total reduction of cold-rolling is 25%, to obtain a cold-rolled sheet;

Heat the cold-rolled sheet to 800°C for 1 min, complete reverse phase transition annealing, and then air-cool to room temperature to obtain a non-yield platform cold-rolled medium manganese steel strip with a thickness of 0.75mm, a tensile strength of 700MPa, and an elongation after fracture of 45%, the organization is composed of lath ferrite and lath austenite structure.

Example 4

Melting molten steel, its composition is to contain C 0.4%, Mn 9%, Si 2%, Al 3%, S0.0012%, P 0.001%, O 0.002%, N 0.003% by mass percentage, and the balance is Fe; Molten steel is poured into the tundish, then poured from the tundish into the cloth flow ladle, and finally poured from the cloth flow ladle into the twin-roll thin strip continuous casting equipment, and cast and rolled to obtain a cast strip with a thickness of 2.2mm;

After the cast strip is cooled to the starting rolling temperature, hot rolling is carried out in one pass. The starting rolling temperature is 1140°C, the total reduction of hot rolling is 15%, and the final rolling temperature is 960°C. After hot rolling, it is air cooled to 430°C for crimping, and hot rolled plate;

Heat the hot-rolled sheet to 750°C for 5 hours, complete reverse phase transition annealing, and obtain reverse phase transition annealed hot-rolled sheet;

Pickling the hot-rolled sheet annealed by reverse phase change annealing to remove scale, and then cold-rolling, the total reduction of cold-rolling is 15%, to obtain a cold-rolled sheet;

Heat the cold-rolled sheet to 720°C for 3 minutes, complete the reverse phase transition annealing, and then air-cool to room temperature to obtain a flat cold-rolled medium manganese steel strip without yield. The thickness is 1.6mm, the tensile strength is 900MPa, and the elongation after fracture is 60%, the structure is composed of lath ferrite and lath austenite structure.

Claims (4)

1. a kind of preparation method of no yield point elongation cold rolling medium managese steel strip, which is characterized in that include the following steps：

(1) melting molten steel, molten steel composition are by mass percentage：C 0.1~0.4%, Mn 3~10%, Si ＜ 2%, Al ＜ 3%, S<0.002%, P<0.002%, O<0.002%, N<0.003%, surplus Fe；

(2) and then by molten steel it is poured into tundish, then is poured into Bu Liubao from tundish, it is thin finally to pour into double roller from Bu Liubao In band continuous casting installation for casting, the Cast Strip that thickness is 1.5~3.0mm is obtained through casting；

(3) Cast Strip is cooled to after start rolling temperature and carries out a time hot rolling, start rolling temperature is 1000~1250 DEG C, under hot rolling stagnation pressure Amount is 10%~30%, and finishing temperature is 900~1150 DEG C, and 300~500 DEG C are air-cooled to after hot rolling and is crimped, hot rolling is obtained Plate；

(4) hot rolled plate is heated to 600~800 DEG C of heat preservation 30min~8h, completes reverse transformation annealing, obtain reverse transformation annealing Hot rolled plate；

(5) the hot rolled plate pickling of reverse transformation annealing being removed into iron scale, then carries out cold rolling, cold rolling overall reduction is 10~ 27%, obtain cold-reduced sheet；

(6) cold-reduced sheet is heated to 600~800 DEG C of heat preservation 1min~12min, completes reverse transformation annealing, then be air-cooled to room temperature, obtains It obtains without yield point elongation cold rolling medium managese steel strip, thickness is 0.75~1.9mm.

2. the preparation method of no yield point elongation cold rolling medium managese steel strip according to claim 1, which is characterized in that described cold It is 1min~12min to roll plate reverse transformation annealing time.

3. the preparation method of no yield point elongation cold rolling medium managese steel strip according to claim 1, which is characterized in that the nothing The tissue of yield point elongation cold rolling medium managese steel strip includes lath columnar ferrite and lath-shaped austenite.

4. the preparation method of no yield point elongation cold rolling medium managese steel strip according to claim 1, which is characterized in that the nothing Engineering stress-strain curve of yield point elongation cold rolling medium managese steel strip have the characteristics that continuously surrender, tensile strength be 700~ 1400MPa, elongation after fracture are 20~60%.