CN117187685A

CN117187685A - Hot dip galvanized dual-phase steel and preparation method thereof

Info

Publication number: CN117187685A
Application number: CN202310915707.4A
Authority: CN
Inventors: 张天越; 李润昌; 苏宝沧; 魏建波; 李钊; 尹文亚; 张士杰; 安方亮
Original assignee: Shougang Jingtang United Iron and Steel Co Ltd
Current assignee: Shougang Jingtang United Iron and Steel Co Ltd
Priority date: 2023-07-25
Filing date: 2023-07-25
Publication date: 2023-12-08

Abstract

The application relates to the technical field of steel manufacturing, in particular to hot dip galvanized dual-phase steel and a preparation method thereof. The steel matrix of the hot dip galvanized dual phase steel comprises the following chemical components: C. mn, si, al, P, S, cr and Fe; wherein, the content of C is 0.04-0.09% by mass, the content of Mn is 1.0-1.5%, the content of Si is 0.1-0.3%, the content of Al is 0.02-0.06%, the content of P is less than or equal to 0.02%, the content of S is less than or equal to 0.003%, and the content of Cr is 0.4-0.7%. The chemical components of the hot dip galvanized dual phase steel replace Mo with Cr, so that the C-Mn-Cr system dual phase steel is developed, the alloy cost is reduced, and the production cost of the existing hot dip galvanized dual phase steel is further reduced.

Description

Hot dip galvanized dual-phase steel and preparation method thereof

Technical Field

The application relates to the technical field of steel manufacturing, in particular to hot dip galvanized dual-phase steel and a preparation method thereof.

Background

In recent years, low cost automotive structural members have received much attention, dual phase steels having low yield ratios and different graded strengths, and being adapted to parts of different forming difficulties in body in white. At present, because of technological limitation, martensite affecting the strength of the hot dip galvanized dual-phase steel is formed by cooling after a zinc pot, and alloy element Mo for improving the hardenability is added into steel to ensure enough strength, so that the Mo alloy has higher price, the cost of the hot dip galvanized dual-phase steel at the present stage is higher, the cost of an automobile is improved, and the long-term development of the automobile industry is not facilitated.

Therefore, there is a need to develop a low cost dual phase steel production process.

Disclosure of Invention

The application provides hot dip galvanized dual phase steel and a preparation method thereof, which are used for solving the technical problem of higher production cost of the existing hot dip galvanized dual phase steel.

In a first aspect, the present application provides a hot dip galvanized dual phase steel, the steel matrix of which comprises the chemical components:

C. mn, si, al, P, S, cr and Fe; wherein, the mass fraction of the material is calculated,

the content of C is 0.04% -0.09%, the content of Mn is 1.0% -1.5%, the content of Si is 0.1% -0.3%, the content of Al is 0.02% -0.06%, the content of P is less than or equal to 0.02%, the content of S is less than or equal to 0.003%, and the content of Cr is 0.4-0.7%.

Optionally, in the chemical composition of the steel matrix of the hot dip galvanized dual phase steel, the content of C is 0.046% -0.053%, the content of Mn is 1.13% -1.23%, the content of Si is 0.142% -0.155%, the content of Al is 0.034% -0.041%, and the content of Cr is 0.545% -0.58%.

Optionally, in the chemical composition of the steel matrix of the hot dip galvanized dual phase steel, the content of C is 0.05%, the content of Mn is 1.2%, the content of Si is 0.15%, the content of Al is 0.03%, the content of P is 0.015%, the content of S is 0.002%, and the content of Cr is 0.58%.

In a second aspect, the present application provides a method for preparing a hot dip galvanized dual phase steel, for preparing the hot dip galvanized dual phase steel according to any embodiment of the first aspect, the method comprising:

heating and rolling the slab for the first time, coiling, and controlling the coiling temperature to obtain a hot rolled coil;

pickling and cold rolling the hot rolled coil, and controlling the total reduction rate of the cold rolling to obtain a chilled coil;

annealing the chilled coil, and then galvanizing to obtain hot dip galvanized dual phase steel; wherein the annealing comprises:

and (3) carrying out secondary heating on the chilled rolls, controlling the end temperature of the secondary heating, and then carrying out staged cooling.

Optionally, the coiling temperature is 520-560 ℃.

Alternatively, the total reduction of the cold rolling is 55-70%.

Optionally, the end point temperature of the second heating is 800-820 ℃.

Optionally, the heating rate of the second heating is 5-12 ℃/s.

Optionally, the staged cooling includes a first cooling and a second cooling; wherein the end temperature of the first cooling is 680-710 ℃, and the end temperature of the second cooling is 440-480 ℃.

Optionally, the cooling speed of the first cooling and the second cooling is 4-9 ℃/s.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:

compared with the traditional hot dip galvanized high-strength steel production strategy, the hot dip galvanized dual-phase steel provided by the embodiment of the application reduces the addition amount of noble alloy, and Cr is used for replacing Mo to develop the C-Mn-Cr system dual-phase steel, so that the alloy cost is reduced, and the production cost of the traditional hot dip galvanized dual-phase steel is further reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.

FIG. 1 is a schematic flow chart of a method for preparing hot dip galvanized dual phase steel according to an embodiment of the application;

fig. 2 is a surface quality chart of a hot dip galvanized dual phase steel provided in example 1 of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

Various embodiments of the application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

In the present application, unless otherwise specified, terms such as "upper" and "lower" are used specifically to refer to the orientation of the drawing in the figures. In addition, in the description of the present specification, the terms "include", "comprising" and the like mean "including but not limited to". Relational terms such as "first" and "second", and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Herein, "and/or" describing an association relationship of an association object means that there may be three relationships, for example, a and/or B, may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. Herein, "at least one" means one or more, and "a plurality" means two or more. "at least one", "at least one" or the like refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

Unless otherwise specifically indicated, the various raw materials, reagents, instruments, equipment and the like used in the present application are commercially available or may be prepared by existing methods.

In some embodiments, the steel matrix of the hot dip galvanized dual phase steel has a chemical composition of 0.046% -0.053% of C, 1.13% -1.23% of Mn, 0.142% -0.155% of Si, 0.034% -0.041% of Al, and 0.545% -0.58% of Cr.

In some embodiments, the steel matrix of the hot dip galvanized dual phase steel has a chemical composition of 0.05% of C, 1.2% of Mn, 0.15% of Si, 0.03% of Al, 0.015% of P, 0.002% of S, and 0.58% of Cr.

In the chemical composition design of the steel matrix of the hot dip galvanized dual phase steel, the addition amount of precious alloy is reduced, cr is used for replacing Mo, the C-Mn-Cr system dual phase steel is developed, the alloy cost is reduced, and the production cost of the existing hot dip galvanized dual phase steel is further reduced.

The positive effect of controlling the content of C to be 0.04% -0.09%: the C element is a reinforcing element of steel, and a certain content of the C element can ensure that the strip steel has enough tensile strength. However, too high a carbon content adversely affects the welding performance; when the carbon content is insufficient, the tensile strength of the strip steel is insufficient. Within the above numerical range, good tensile strength and weldability can be obtained. Specifically, the content of C may be 0.04%, 0.06%, 0.09%, or the like.

The positive effect of controlling the Mn content to be 1.0% -1.5%: the tensile strength of the strip steel is ensured. When the Mn content is insufficient, the tensile strength is insufficient. Specifically, the Mn content may be 1.0%, 1.3%, 1.5%, etc.

The positive effect of controlling the content of Si to be 0.1-0.3 percent: the tensile strength of the strip steel is ensured, and the hardenability is improved. When the Si content is too high, red rust is generated, and the surface quality of hot galvanizing is affected. Specifically, the content of Si may be 0.1%, 0.2%, 0.3%, or the like.

The positive effect of controlling the content of Al to be 0.02% -0.06%: is convenient for regulating and controlling the content of other components. Too high an Al content causes difficulties in steelmaking. Specifically, the content of Al may be 0.02%, 0.04%, 0.06%, or the like.

The positive effect of controlling the content of P to be less than or equal to 0.02 percent is that: too high a P content can reduce the strip plasticity. Specifically, the content of P may be 0.02%, 0.01%, or the like.

The positive effect of controlling the S content to be less than or equal to 0.003 percent is that: too high a content of S may reduce the plasticity and weldability of the strip. Specifically, the content of S may be 0.003%, 0.002%, 0.0025%, etc.

The positive effect of controlling the Cr content to be 0.4-0.7 percent: the hardenability of the strip steel is improved, and meanwhile, cr element is used for replacing Mo element in the embodiment of the application, so that the strip steel has enough tensile strength. If the Cr content is too high, poor surface quality can be caused to a certain extent, and obvious chromatic aberration appears on the surface after hot galvanizing; if the Cr content is too low, the hardenability of the strip steel is insufficient to a certain extent, and the tensile strength is insufficient. Specifically, the Cr content may be 0.4%, 0.5%, 0.6%, 0.7%, etc.

Preferably, the content of C is 0.046% -0.053%, the content of Mn is 1.13% -1.23%, the content of Si is 0.142% -0.155%, the content of Al is 0.034% -0.041%, and the content of Cr is 0.545-0.58%.

More preferably, the content of C is 0.05%, the content of Mn is 1.2%, the content of Si is 0.15%, the content of Al is 0.03%, the content of P is 0.015%, the content of S is 0.002%, and the content of Cr is 0.58%.

In a second aspect, the present application provides a method for preparing a hot dip galvanized dual phase steel, referring to fig. 1, for preparing a hot dip galvanized dual phase steel according to any embodiment of the first aspect, the method comprising:

s1, performing first heating and rolling on a slab, coiling, and controlling the coiling temperature to obtain a hot rolled coil;

in some embodiments, the temperature of the coiling is 520-560 ℃.

In the embodiment of the application, the coiling temperature is controlled to be 520-560 ℃ and has the positive effects that: the proper coiling temperature can lead the strip steel to be uniform in structure, regulate and control the property of rolling structure and control the red rust defect. If the coiling temperature is too high, cr element, fe and O element in the steel can form oxide scales which are difficult to remove to a certain extent, so that red rust defects are caused, and the defects are transmitted to a hot galvanizing process to cause surface color difference; if the coiling temperature is too low, the overall strength of the hot rolled coil can be increased to a certain extent, the rolling load is large during cold rolling, meanwhile, the difficulty in controlling the cooling uniformity of the strip steel edge is increased, the cooling is uneven, the edge structure is hardened, and the edge fracture strip is easy to occur during cold rolling. Specifically, the winding temperature may be 520 ℃, 540 ℃, 560 ℃, or the like.

The first heating means heating in a furnace, wherein the heating temperature of a plate blank is 1190-1290 ℃, the heat preservation time of heating is 190-210min, the rolling comprises rough rolling, the rough rolling temperature is 1050-1120 ℃, and the rolling finishing temperature is 880-920 ℃.

S2, carrying out acid washing and cold rolling on the hot rolled coil, and controlling the total rolling reduction of the cold rolling to obtain a chilled coil;

in some embodiments, the cold rolling has a total reduction of 55 to 70%.

In the embodiment of the application, the cold rolling adopts 5-pass rolling. The positive effect of controlling the total rolling reduction of the cold rolling to be 55-70 percent: the strip steel can obtain proper cold rolling thickness, and is convenient for hot rolling and cold rolling production. If the total rolling reduction of the cold rolling is too high, the strip steel is work hardened to a certain extent, and meanwhile, the rolling force is too high during rolling and the rolling is difficult because the coiling temperature of the hot rolling is controlled to be lower; if the total rolling reduction of the cold rolling is too low, the thickness of the hot rolled coil is too thick to a certain extent, hot rolling is difficult, and the surface quality of the strip steel is also affected. Specifically, the total reduction of the cold rolling may be 55%, 60%, 65%, 70%, or the like.

The technological parameters of the pickling include: the concentration of hydrochloric acid is 42-54g/L, and the temperature of acid liquor is 72-87 ℃.

S3, annealing the chilled coil, and then galvanizing to obtain hot galvanized dual-phase steel; wherein the annealing comprises: and (3) carrying out secondary heating on the chilled rolls, controlling the end temperature of the secondary heating, and then carrying out staged cooling.

In some embodiments, the end point temperature of the second heating is 800-820 ℃.

In some embodiments, the second heating has a ramp rate of 5-12 ℃/s.

In the embodiment of the application, the 'end point temperature of the second heating' represents the annealing temperature, and the positive effect of controlling the annealing temperature to be 800-820 ℃ is that: and the strip steel work hardening is completely eliminated, and meanwhile, the austenitic phases with different proportions are regulated and controlled. If the annealing temperature is too high, the austenitizing degree in the strip steel in the embodiment of the application is too high to a certain extent, the tensile strength and the yield strength are both increased after cooling, and the plasticity is reduced; if the annealing temperature is too low, the strip steel is still work hardened to some extent, and formability is lowered. Specifically, the annealing temperature may be 800 ℃, 810 ℃, 820 ℃, or the like. Preserving heat for 1-3min at the annealing temperature.

In the embodiment of the application, the positive effect of controlling the heating rate of the second heating to be 5-12 ℃/s is that: ensuring that the grain growth speed is in a proper range, and too low and too high influence the tensile strength.

In some embodiments, the staged cooling includes a first cooling and a second cooling; wherein the end temperature of the first cooling is 680-710 ℃, and the end temperature of the second cooling is 440-480 ℃.

In some embodiments, the cooling rate of both the first cooling and the second cooling is 4-9 ℃/s.

In the embodiment of the application, the positive effect of cooling is carried out in stages: the proportion of ferrite and austenite in the strip steel is convenient to regulate and control, and the proportion of heavy ferrite and martensite of the final dual-phase steel finished product is controlled.

The first cooling adopts a slow cooling mode, the end temperature of the first cooling is the slow cooling temperature, and the positive effects of controlling the end temperature of the first cooling to 680-710 ℃ are that: the ferrite ratio is controlled. When the slow cooling temperature is less than 680 ℃, the ferrite proportion is lower, and the tensile strength of the strip steel in the embodiment of the application is insufficient; when the slow cooling temperature is higher than 710 ℃, the tensile strength of the strip steel in the embodiment of the application is increased. Specifically, the end temperature of the first cooling may be 680 ℃, 700 ℃, 710 ℃, or the like. Preserving heat for 1-2min at the end temperature of the first cooling.

The second cooling adopts a quick cooling mode, the end temperature of the second cooling is the quick cooling temperature, and the end temperature of the second cooling is controlled to be 440-480 ℃ and has the positive effects that: the temperature of the subsequent strip steel entering the pot is controlled, and the coating property and the finished product performance are ensured. Too low results in poor plating properties, resulting in dezincification; too high tempers the strip more fully, reducing the tensile strength. Specifically, the end temperature of the second cooling may be 440 ℃, 460 ℃, 480 ℃, or the like.

The positive effect of controlling the cooling speed of the first cooling and the second cooling to be 4-9 ℃/s: controlling the proportion of each structure in the strip steel, and changing austenite into martensite at an excessively high cooling speed to increase the tensile strength; too low a cooling rate does not reach the end temperature of the second cooling at a certain belt speed. Specifically, the cooling rate may be 4 ℃/s, 6 ℃/s, 9 ℃/s, or the like.

And after the second cooling, the zinc is put into a zinc pot for hot galvanizing, and the aluminum content of the zinc pot is 0.22 to 0.26 percent by mass percent. Cooling after hot galvanizing, wherein the temperature of a roller at the top of the cooling tower reaches 150-200 ℃. After cooling, finishing by a finishing machine, wherein the finishing elongation is 0.8-1.2%.

On the basis of the low-cost chemical components provided in the first aspect, the hot dip galvanized dual-phase steel with tensile strength more than 450MPa, yield strength more than 270MPa, elongation at 80mm of gauge length more than 32% and hole expansion rate more than 50% is finally prepared by combining hot rolling, cold rolling, annealing and galvanization matching technology, regulating and controlling the high Cr surface at low temperature coiling and high pressure, high temperature annealing and two-stage cooling, ensuring the performance, defining key control points such as heating speed and cooling speed, and the like, thereby reducing the production cost and improving the forming performance.

The preparation method of the hot dip galvanized dual phase steel is realized based on the hot dip galvanized dual phase steel, and specific steps of chemical components of the hot dip galvanized dual phase steel can refer to the embodiment, and as the preparation method of the hot dip galvanized dual phase steel adopts part or all of the technical schemes of the embodiment, the preparation method at least has all the beneficial effects brought by the technical schemes of the embodiment, and the description is omitted.

The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. The experimental procedures, which are not specified in the following examples, are generally determined according to national standards. If the corresponding national standard does not exist, the method is carried out according to the general international standard, the conventional condition or the condition recommended by the manufacturer.

The application provides a preparation method of hot dip galvanized dual phase steel, which comprises the following steps:

s3, annealing the chilled coil, and then galvanizing to obtain hot galvanized dual-phase steel; wherein the annealing comprises: and (3) carrying out secondary heating on the chilled rolls, controlling the end temperature of the secondary heating, and then carrying out staged cooling. For specific process parameters, please see the examples section below.

Example 1

The specification of the cold-rolled steel coil is 2.0 multiplied by 1395mm, and the weight percentage of the steel coil components is as follows: the slab comprises the following chemical components in percentage by mass: c:0.052%, mn:1.23%, si:0.151%, al:0.036%, P:0.008%, S:0.0014%, cr:0.545%, heating and preserving time 194min, rough rolling temperature 1097%, final rolling temperature 910 ℃, coiling temperature 533 ℃, hydrochloric acid concentration 50g/L, acid liquor temperature 75 ℃, total reduction rate of cold rolling 63.64%, annealing temperature 813 ℃, heating speed 8 ℃/s, preserving 1.5min, slow cooling temperature 704 ℃, cooling speed 5 ℃/s, preserving 1.2min, quick cooling temperature 457 ℃, cooling speed 5 ℃/s, aluminum content of a zinc pot in mass fraction of 0.23%, top roller temperature 165 ℃ and finishing elongation 1.13%.

Mechanical properties: tensile strength 472MPa, yield strength 283MPa, elongation 34% at gauge length 80mm and hole expansion 57%.

Example 2

The specification of the cold-rolled steel coil is 1.2 multiplied by 1275mm, and the weight percentage of the steel coil components is as follows: the slab comprises the following chemical components in percentage by mass: c:0.053%, mn:1.22%, si:0.155%, al:0.034%, P:0.009%, S:0.0019%, cr:0.556 percent, heating and preserving time 197min, rough rolling temperature 1091 percent, final rolling temperature 903 percent, coiling temperature 541 percent, hydrochloric acid concentration 51g/L, the acid liquor temperature 77 percent, total reduction rate of cold rolling of 60 percent, 5-pass rolling, annealing temperature 809 percent, heating speed 7 ℃/s, preserving 1.4min, slow cooling temperature 697 ℃, cooling speed 5 ℃/s, preserving 1.2min, quick cooling temperature 461 percent, cooling speed 5 ℃/s, aluminum content of a zinc pot in mass fraction of 0.24 percent, top roller temperature 171 percent, and finishing elongation of 1.17 percent.

Mechanical properties: tensile strength 461MPa, yield strength 281MPa, elongation 32% at gauge length 80mm and hole expansion ratio 54%.

Example 3

The specification of the cold-rolled steel coil is 1.6X105 mm, and the weight percentage of the steel coil components is as follows: the slab comprises the following chemical components in percentage by mass: c:0.046%, mn:1.13%, si:0.142%, al:0.041%, P:0.009%, S:0.0018%, cr:0.556 percent, heating and heat preserving time 203min, rough rolling temperature 1102 percent, final rolling temperature 894 percent, coiling temperature 546 percent, hydrochloric acid concentration 47g/L, acid liquor temperature 73 percent, total reduction rate of cold rolling of 64.4 percent, annealing temperature 817 percent by adopting 5-pass rolling, heating speed of 8 percent/s, heat preserving for 1.5min, slow cooling temperature 703 percent, cooling speed of 4 percent/s, heat preserving for 1.3min, quick cooling temperature 459 percent, cooling speed of 4 percent/s, aluminum content of a zinc pot of 0.26 percent in mass percent, tower top roller temperature 168 percent, and finishing elongation of 1.04 percent.

Mechanical properties: tensile strength 477MPa, yield strength 292MPa, elongation at gauge length 80mm 33% and hole expansion rate 56%.

Example 4

The specification of the cold-rolled steel coil is 1.2 multiplied by 1450mm, and the weight percentages of the components of the steel coil are as follows: the slab comprises the following chemical components in percentage by mass: c:0.05%, mn:1.2%, si:0.15%, al:0.03%, P:0.015%, S:0.002%, cr:0.58%, heating and preserving time 205min, rough rolling temperature 1102 ℃, final rolling temperature 894 ℃, coiling temperature 560 ℃, hydrochloric acid concentration 54g/L, wherein the acid liquor temperature 80 ℃, total reduction rate of cold rolling are 70%, 5-pass rolling is adopted, annealing temperature 817 ℃, heating speed 8 ℃/s, preserving 1.5min, slow cooling temperature 703 ℃, cooling speed 7 ℃/s, preserving 1.3min, quick cooling temperature 459 ℃, cooling speed 7 ℃/s, aluminum content of a zinc pot in mass percent is 0.26%, tower top roller temperature 168 ℃, finishing elongation 1.04%.

Mechanical properties: tensile strength 491MPa, yield strength 295MPa, elongation 30% at gauge length 80mm and hole expansion 54%.

Example 5

The specification of the cold-rolled steel coil is 1.6X101 mm, and the weight percentage of the steel coil components is as follows: the slab comprises the following chemical components in percentage by mass: c:0.09%, mn:1.5%, si:0.3%, al:0.06%, P:0.009%, S:0.0018%, cr:0.69%, heating and preserving time is 190min, rough rolling temperature 1120 ℃, final rolling temperature 920 ℃, coiling temperature 520 ℃ and hydrochloric acid concentration 42g/L, wherein the acid liquor temperature is 72 ℃, the total reduction rate of cold rolling is 55%, 5-pass rolling is adopted, annealing temperature is 800 ℃, heating speed is 12 ℃/s, preserving temperature is 1.5min, slow cooling temperature is 680 ℃, cooling speed is 4 ℃/s, preserving temperature is 1.3min, fast cooling temperature is 440 ℃, cooling speed is 4 ℃/s, aluminum content of a zinc pot is 0.26% in mass fraction, the temperature of a top roller is 168 ℃, and finishing elongation is 1.04%.

Mechanical properties: the tensile strength is 481MPa, the yield strength is 265MPa, the elongation rate at the gauge length is 32% and the reaming rate is 59%.

Comparative example 1

The specification of the cold-rolled steel coil of the comparative example is 1.6X105 mm, and the weight percentage of the components of the steel coil is as follows: the slab comprises the following chemical components in percentage by mass: c:0.056%, mn:1.31%, si:0.14%, al:0.04%, P:0.011%, S:0.002%, mo:0.12%, heating and preserving time 201min, rough rolling temperature 1097%, final rolling temperature 891 ℃, coiling temperature 621 ℃, hydrochloric acid concentration 50g/L, acid liquor temperature 75 ℃, total reduction rate of cold rolling 64.4%, annealing temperature 800 ℃, heating speed 11 ℃/s, preserving 1.5min, slow cooling temperature 701 ℃, cooling speed 4 ℃/s, preserving 1.2min, fast cooling temperature 453 ℃, cooling speed 5 ℃/s, zinc pot aluminum content 0.23% in mass fraction, tower top roller temperature 177 ℃, finishing elongation 1.1%.

Mechanical properties: tensile strength 465MPa, yield strength 281MPa, elongation at gauge length 80mm 52% and hole expansion rate 38%.

Comparative example 1

The specification of the cold-rolled steel coil of the comparative example is 1.2 multiplied by 1275mm, and the weight percentage of the steel coil components is as follows: the slab comprises the following chemical components in percentage by mass: c:0.053%, mn:1.22%, si:0.155%, al:0.034%, P:0.009%, S:0.0019%, cr:0.556 percent, heating and preserving time 197min, rough rolling temperature 1091 percent, final rolling temperature 903 percent, coiling temperature 541 percent, hydrochloric acid concentration 51g/L, acid liquor temperature 77 percent, total reduction rate of cold rolling of 60 percent, 5-pass rolling, annealing temperature 780 percent, heating speed 7 ℃/s, preserving 1.4min, slow cooling temperature 672 percent, cooling speed 5 ℃/s, preserving 1.2min, quick cooling temperature 455 percent, cooling speed 5 ℃/s, aluminum content of a zinc pot of 0.24 percent in mass fraction, top roller temperature 176 percent and finishing elongation of 1.13 percent.

Mechanical properties: tensile strength 436MPa, yield strength 241MPa, elongation 36% at gauge length 80mm and hole expansion 42%.

Through the above examples 1-5, the alloy cost is reduced by replacing Mo with Cr, and the hot dip galvanized dual phase steel prepared by combining the hot rolling, cold rolling, annealing and galvanization matching process has the key control points of low temperature coiling, high pressure regulation and control of the high Cr surface, high temperature annealing, two sections of cooling guarantee performance, clear heating speed, cooling speed and the like, and has excellent mechanical properties. Further, referring to the surface quality chart of the hot dip galvanized dual phase steel provided in example 1 of fig. 2, it can be seen that the steel sheet has excellent surface quality.

In the embodiment of the application, cr is used for replacing Mo to reduce the alloy cost. Comparative example 3 and comparative example 1, the alloy cost of example 3 was about 541 yuan/ton, the alloy cost of comparative example 1 was about 765 yuan/ton, the cost of 224 yuan/ton was reduced by Cr instead of Mo alloy, and no significant difference was found in mechanical properties and hole expansibility.

In comparative example 2, the annealing temperature was too low and the slow cooling temperature was too low, and the mechanical properties of the final hot dip galvanized dual phase steel were inferior to those of the examples of the present application.

The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The hot dip galvanized dual phase steel is characterized in that the chemical components of a steel matrix of the hot dip galvanized dual phase steel comprise:

the content of C is 0.04-0.09%, the content of Mn is 1.0-1.5%, the content of Si is 0.1-0.3%, the content of Al is 0.02-0.06%, the content of P is less than or equal to 0.02%, the content of S is less than or equal to 0.003%, and the content of Cr is 0.4-0.7%.

2. The hot dip galvanized dual phase steel according to claim 1, characterized in that the content of C is 0.046-0.053%, the content of Mn is 1.13-1.23%, the content of Si is 0.142-0.155%, the content of Al is 0.034-0.041%, and the content of Cr is 0.545-0.58% in the chemical composition of the steel matrix of the hot dip galvanized dual phase steel.

3. The hot dip galvanized dual phase steel according to claim 1, characterized in that the content of C is 0.05%, the content of Mn is 1.2%, the content of Si is 0.15%, the content of Al is 0.03%, the content of P is 0.015%, the content of S is 0.002%, and the content of Cr is 0.58% in the chemical composition of the steel matrix of the hot dip galvanized dual phase steel.

4. A method for preparing a hot dip galvanised dual phase steel, characterized in that it is used for preparing a hot dip galvanised dual phase steel according to any of claims 1-3, said method comprising:

annealing the chilled coil, and then galvanizing to obtain hot dip galvanized dual phase steel; wherein the annealing comprises: and (3) carrying out secondary heating on the chilled rolls, controlling the end temperature of the secondary heating, and then carrying out staged cooling.

5. The method of claim 4, wherein the temperature of the coiling is 520-560 ℃.

6. The method according to claim 4, wherein the total reduction of the cold rolling is 55-70%.

7. The method of claim 4, wherein the second heating has an end point temperature of 800-820 ℃.

8. The method of claim 4 or 7, wherein the second heating is at a ramp rate of 5-12 ℃/s.

9. The method of claim 4, wherein the staged cooling comprises a first cooling and a second cooling; wherein the end temperature of the first cooling is 680-710 ℃, and the end temperature of the second cooling is 440-480 ℃.

10. The method of claim 9, wherein the cooling rates of the first and second cooling are each 4-9 ℃/s.