CN116445811A

CN116445811A - 420MPa grade stainless steel composite board and preparation method thereof

Info

Publication number: CN116445811A
Application number: CN202310179665.2A
Authority: CN
Inventors: 镇凡; 曲锦波; 邵春娟; 杨浩
Original assignee: Jiangsu Shagang Group Co Ltd; Zhangjiagang Hongchang Steel Plate Co Ltd; Jiangsu Shagang Iron and Steel Research Institute Co Ltd
Current assignee: Jiangsu Shagang Group Co Ltd; Zhangjiagang Hongchang Steel Plate Co Ltd; Jiangsu Shagang Iron and Steel Research Institute Co Ltd
Priority date: 2023-02-28
Filing date: 2023-02-28
Publication date: 2023-07-18

Abstract

The invention discloses a 420MPa grade stainless steel composite board and a preparation method thereof. The chemical components of the base layer of the composite board are as follows by mass percent: c:0.05 to 0.09 percent, si:0.14 to 0.22 percent, mn:1.41 to 1.49 percent, cr:0.16 to 0.24 percent, ni:0.11 to 0.19 percent, mo:0.11 to 0.19 percent, nb: 0.021-0.029%, ti: 0.011-0.019%, al:0.030 to 0.040 percent and the balance of Fe; the yield strength of the composite board is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after fracture is more than or equal to 18%, and the yield ratio is less than or equal to 0.85; the interface bonding rate of the composite board is 100%, the shearing strength is more than or equal to 300MPa, and the unevenness is less than or equal to 3mm/m. Also has excellent surface quality.

Description

420MPa grade stainless steel composite board and preparation method thereof

Technical Field

The invention belongs to the technical field of steel material preparation, and relates to a 420MPa grade stainless steel composite board and a preparation method thereof.

Background

With the continuous development of science and industry, common alloy or single metal is difficult to meet the requirement of industrial development on the comprehensive performance of materials, and composite boards are generated. The stainless steel composite board takes carbon steel or low alloy steel as a base layer, takes stainless steel as a multi-layer, and realizes metallurgical bonding of a composite interface by methods of explosive cladding, rolling cladding and the like, so that the resources are saved and the cost is reduced on the premise of not reducing the using effect (mechanical strength, corrosion resistance and the like). The stainless steel composite board is widely applied to industries such as petrochemical industry, pressure vessels, power equipment, medical equipment, water conservancy, papermaking, bridges and the like.

In recent years, with the continuous improvement of requirements on safety, long service life and the like of a steel bridge, the rust prevention and corrosion prevention problems of a steel bridge structure are more and more prominent, and if a layer of corrosion-resistant protective material is coated on the surface of bridge steel, the corrosion-resistant protective material is used for replacing a single bridge steel plate, so that the long-term corrosion prevention target which cannot be achieved by a spraying process can be realized. Therefore, the stainless steel composite plate is a ideal choice.

The existing stainless steel composite board adopts modes of explosive cladding, non-vacuum preparation of composite blanks, vacuum electron beam welding blank making and the like, and has the problems of poor surface quality, difficult control of the plate shape, poor interface bonding quality, low yield, low production efficiency and the like.

Disclosure of Invention

The invention aims to provide a 420MPa grade stainless steel composite board and a preparation method thereof, wherein the stainless steel composite board has excellent surface quality, board shape and interface bonding quality.

In order to achieve the aim of the invention, one embodiment of the invention provides a 420MPa grade stainless steel composite board, the total thickness of the composite board is 5-55 mm, the thickness of a base layer is 4-45 mm, the thickness of a composite layer is 1-10 mm, the structure is a bainite+ferrite structure, the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after fracture is more than or equal to 18%, and the yield ratio is less than or equal to 0.85; the composite interface bonding rate of the composite board is 100%, the shearing strength is more than or equal to 300MPa, and the unevenness is less than or equal to 3mm/m.

Preferably, the chemical components of the base layer of the composite board are as follows in percentage by mass: c:0.05 to 0.09 percent, si:0.14 to 0.22 percent, mn:1.41 to 1.49 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.0020 percent, cr:0.16 to 0.24 percent, ni:0.11 to 0.19 percent, mo:0.11 to 0.19 percent, nb: 0.021-0.029%, ti: 0.011-0.019%, al:0.030 to 0.040 percent, and the balance of Fe and unavoidable impurities.

Preferably, the composite board comprises the following chemical components in percentage by mass: c is less than or equal to 0.15%, si is less than or equal to 1.00%, mn is less than or equal to 2.00%, P is less than or equal to 0.045%, S is less than or equal to 0.030%, ni:6.0 to 22.0 percent, cr:16.0 to 26.0 percent, mo is less than or equal to 3.0 percent, and the balance is Fe and unavoidable impurities.

Preferably, the impact energy of the composite board at 0 ℃ is more than or equal to 120J, the impact energy of the composite board at-20 ℃ is more than or equal to 120J, and the impact energy of the composite board at-40 ℃ is more than or equal to 120J; the composite board is bent outwards by 180 degrees without cracks, and bent inwards by 180 degrees without cracks; boiling in sulfuric acid-copper sulfate solution for 20h, and bending at 180 degrees to obtain the composite layer without intergranular corrosion crack.

In order to achieve the above object, an embodiment of the present invention provides a method for preparing a 420MPa grade stainless steel composite board, which includes the following steps:

1) Preparation of composite blank

Preparing two carbon steel billets with thickness T1, length L1 and width W1 as base materials; preparing two stainless steel billets with thickness T2, length L2 and width W2 as composite materials; l2 is less than L1, W2 is less than W1;

Carrying out surface treatment on at least one surface of each of the two base materials and the two composite materials;

coating a release agent on one surface of a composite material;

assembling according to the stacking sequence of the base material, the composite material and the base material; the composite material is placed in the middle relative to the base material, the surfaces of the base material and the composite material, which are contacted with each other, are both surfaces subjected to surface treatment, and the surface of the isolating agent is coated on the other composite material;

four sealing strips with the width W3 are prepared, the W3 = 2T 2-1-2 mm, the sealing strips are attached to the four sides of two composite materials, gas shielded welding is carried out between the adjacent sealing strips and between the sealing strips and the base materials, so that the two base materials and the sealing strips form a whole, and a composite blank base blank is obtained;

a round hole is processed on the seal at the groove of the side edge of the composite blank base blank, and a seamless steel tube is welded at the round hole;

overlaying the grooves on the four sides of the composite blank base blank;

vacuumizing the composite blank through the seamless steel pipe by adopting a vacuum pump, wherein the vacuum degree is less than or equal to 10 ^-1 Pa, and then maintaining the pressure for more than 4 hours; finally, sealing the seamless steel tube;

2) Rolling of composite billets

Heating the obtained composite blank at 1180-1200 ℃ for a total heating time of not less than 1.2×tmin/mm, wherein t is the thickness of the composite blank, and the soaking period is 30-50 min;

The method comprises the steps of adopting two-stage control rolling of rough rolling and finish rolling, wherein in the rough rolling stage, the initial rolling temperature is less than or equal to 1040 ℃, the final rolling temperature is more than or equal to 1000 ℃, transverse rolling is performed firstly, then longitudinal rolling is performed, at least one pass of rolling reduction is more than or equal to 35mm in the longitudinal rolling process, the total rolling reduction of rough rolling is 40-60%, and the rough rolling stage is finished when the thickness of an intermediate blank is 2.5-3.5 times of the target thickness of a large plate of the composite plate; then, when the temperature is kept, watering and cooling are carried out during the period, and when the surface temperature of the intermediate blank is reduced to below 840 ℃, the finish rolling stage is started; the finishing temperature in the finish rolling stage is more than or equal to 810 ℃, and the total rolling reduction of the finish rolling is 55-75%, so that a composite board large plate is obtained;

after rolling, the large composite plate enters an ultra-fast cooling system for cooling, the cooling temperature is more than or equal to 740 ℃, the cooling speed is 10-20 ℃/s, and the final cooling temperature is 510-530 ℃;

directly feeding the large composite board leaving the ultra-rapid cooling system into a straightener for straightening;

3) Composite board separation straightening

Cutting four sides of a large composite board to remove parts outside the seal, and separating the large composite board into an upper composite board small board and a lower composite board small board;

and (5) transversely flattening and cold straightening the small plates of the composite plate to obtain a stainless steel composite plate finished product.

Preferably, the step of "subjecting at least one surface of each of the two base materials and the two composite materials to surface treatment" includes:

Milling one surface of two base materials in a mode of complementation of relative shapes, processing the surface into irregular concave-convex surfaces comprising n planes which are sequentially connected in the transverse direction, wherein the base materials are non-uniform thickness blanks with non-monotonic thickness changes in the transverse direction, the length L12=L1 of the irregular concave-convex surfaces and the total width W12 is larger than W1; or, processing the surface into an irregular concave-convex surface comprising n planes which are sequentially connected along the longitudinal direction, wherein the base material is a non-uniform thickness blank with non-monotonic thickness change along the longitudinal direction, the total length L12 of the irregular concave-convex surface is more than L1, and the width W12=W1; n is more than or equal to 2;

polishing one surface of each composite material to remove surface oxide skin; and then each composite material is bent to be matched with the corresponding irregular concave-convex surface.

polishing one surface of each composite material to remove surface oxide skin; the method comprises the steps of,

and milling one surface of the two substrates in a manner of complementarily forming, wherein the surface is processed into a transverse inclined surface with the length of L11=L1 and the width of W11 & gtW 1, the substrate is a non-uniform thick blank with the thickness gradually changing in the transverse direction, or the surface is processed into a longitudinal inclined surface with the length of L11 & gtL 1 and the width of W11 & gtW 1, and the substrate is a non-uniform thick blank with the thickness gradually changing in the longitudinal direction.

Preferably, the step of "subjecting at least one surface of each of the two base materials and the two composite materials to surface treatment" includes: and polishing one surface of each base material and each composite material to remove surface oxide skin.

Preferably, in the "the composite is placed centrally with respect to the substrate", the distance from the lateral side of the composite to the corresponding side of the substrate is half the difference in width between the contact surfaces of the composite and the substrate, and the distance from the longitudinal side of the composite to the corresponding side of the substrate is half the difference in length between the contact surfaces of the composite and the substrate.

Preferably, after the step of directly straightening the large composite board which leaves the ultra-rapid cooling system and directly enters the straightener, the cooling bed on the straightened large composite board is naturally cooled, and when the surface temperature is reduced to below 200 ℃, the cold straightening is carried out by adopting a cold straightener.

Preferably, after the step of directly entering the straightener for straightening after the large composite board leaves the ultra-rapid cooling system:

placing the straightened composite board big board between two steel boards with the temperature of Tf-50-Tf for stacking cooling, wherein the stacking cooling time is 0.4min/mm multiplied by 0+/-5 min, and T0 is the thickness of the composite board big board;

naturally cooling the cooling bed on the large composite board after the cold stacking is finished;

T _f ＝550+30[Si]-20[Mn]+15[Cr]-15[Ni]+10[Mo]Wherein [ Si ]]、[Mn]、[Mo]、[Cr]、

[ Ni ] is 100 times of the mass percentage of each element in the base material.

Preferably, in the step of performing overlaying welding on grooves on four sides of the composite blank base blank, submerged arc overlaying welding is adopted;

before welding, baking the welding flux for 2 hours at 350 ℃, and then preserving heat for 1 hour at 150 ℃;

in the welding process, the temperature between the control channels is 135-165 ℃, the welding current is 570-630A, the welding voltage is 28-32V, and the welding speed is 420-480 mm/min.

Preferably, in the step of performing gas shielded welding between adjacent seals and between the seal and the base material, the welding current is 260-290A, the welding voltage is 24-28V, the welding speed is 300-360 mm/min, and the temperature between the seal and the base material is controlled to be 135-165 ℃ in the welding process.

Compared with the prior art, the invention has the beneficial effects that: the composite board has the advantages of excellent surface quality, excellent board shape, excellent interface bonding and the like, for example, obvious surface defects such as pits, side scratches and the like of the existing composite board are avoided, for example, the unevenness of the composite board is less than or equal to 3mm/m, the bonding rate of the composite interface of the composite board is 100%, the shearing strength is more than or equal to 300MPa, the composite board has excellent mechanical properties, the total thickness of the composite board is 5-55 mm, the thickness of a base layer is 4-45 mm, the thickness of a composite layer is 1-10 mm, the structure is a bainite+ferrite structure, the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after breaking is more than or equal to 18%, and the yield ratio is less than or equal to 0.85.

Drawings

In the various illustrations of the invention, certain dimensions of structures or portions are exaggerated relative to other structures or portions for clarity of illustration and description, and thus serve only to illustrate the basic structure of the inventive subject matter.

FIG. 1a is a schematic cross-sectional view of a billet according to a first embodiment of the billet surface treatment step of the present invention;

fig. 1b is a schematic transverse cross-section of a billet according to a second embodiment of the blank surface treatment step of the invention, wherein the surface shape change after the surface treatment is indicated by dash-dot lines;

fig. 1c is a schematic longitudinal cross-sectional view of a billet according to a third embodiment of the blank surface treatment step of the present invention, wherein the change in surface shape after surface treatment is indicated by dash-dot lines;

fig. 1d is a schematic transverse cross-sectional view of a billet according to a fourth embodiment of the blank surface treatment step in the present invention, and illustrates the change in surface shape before (a) and after (B) the surface treatment;

fig. 1e is a schematic longitudinal cross-sectional view of a billet according to a fifth embodiment of the blank surface treatment step in the present invention, and illustrates the change in surface shape before (a) and after (B) the surface treatment;

FIG. 2a is a schematic cross-sectional view of a composite blank corresponding to FIG. 1 a;

FIG. 2b is a schematic transverse cross-sectional view of a composite blank corresponding to FIG. 1 b;

FIG. 2c is a schematic longitudinal cross-sectional view of a composite blank corresponding to FIG. 1 c;

FIG. 2d is a schematic transverse cross-sectional view of a composite blank corresponding to FIG. 1 d;

FIG. 2e is a schematic longitudinal cross-sectional view of a composite blank corresponding to FIG. 1 e;

FIG. 3a is a block flow diagram of steps for rolling a composite billet according to an embodiment of the present invention;

FIG. 3b is a block flow diagram of the steps of rolling a composite billet according to yet another embodiment of the present invention;

FIG. 4a is a schematic cross-sectional view of two composite panels rolled from the composite blank of FIG. 2 a;

FIG. 4b is a schematic transverse cross-sectional view of two composite panels rolled from the composite blank of FIG. 2 b;

FIG. 4c is a schematic longitudinal cross-sectional view of two composite panels rolled from the composite blank of FIG. 2 c;

FIG. 4d is a schematic transverse cross-sectional view of two composite panels rolled from the composite blank of FIG. 2 d;

fig. 4e is a schematic longitudinal cross-sectional view of two composite panels rolled from the composite blank of fig. 2 e.

Detailed Description

The invention provides a preparation method of a 420MPa grade stainless steel composite board and a composite board prepared based on the method.

Compared with the prior art, such as explosive cladding, non-vacuum preparation of a composite blank, vacuum electron beam welding blank making and the like, the composite plate prepared by the preparation method has the advantages of excellent surface quality, excellent plate shape, excellent interface bonding and the like, such as no obvious surface defects of pits, side scratches and the like of the existing composite plate, such as the unevenness of the composite plate is less than or equal to 3mm/m, the bonding rate of the composite interface of the composite plate is 100%, the shearing strength is more than or equal to 300MPa, and the composite plate also has excellent mechanical properties, the total thickness of the composite plate is 5-55 mm, the thickness of a base layer is 4-45 mm, the thickness of a composite layer is 1-10 mm, the structure is a bainite+ferrite structure, the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after breaking is more than or equal to 18%, and the yield ratio is less than or equal to 0.85.

Specifically, the preparation method comprises three general steps of composite blank preparation, composite blank rolling and composite plate separation and straightening.

The total steps of the preparation of the composite blank comprise the following sub-steps:

preparing two carbon steel billets with thickness T1, length L1 and width W1 as base materials; preparing two stainless steel billets with thickness T2, length L2 and width W2 as composite materials;

coating a release agent on one surface of a composite material;

assembling according to the stacking sequence of the base material, the composite material and the base material;

overlaying the grooves on the four sides of the composite blank base blank;

vacuumizing the composite blank through the seamless steel pipe by adopting a vacuum pump, wherein the vacuum degree is less than or equal to 10 ^-1 Pa, and then maintaining the pressure for more than 4 hours; and finally, sealing the seamless steel tube.

Further, the above sub-steps are described in detail as follows.

Step "preparing two carbon steel billets with length L1 and width W1 as base materials; and preparing two stainless steel billets with the length L2 and the width W2 as composite materials ", namely a billet preparation step.

Wherein, the thickness T1, the length L1 and the width W1 of the carbon steel billet serving as the base material are rectangular billets; similarly, the stainless steel billet as the composite material is also rectangular in thickness T2, length L2, and width W2. And L2 is smaller than L1, W2 is smaller than W1, and the length and width dimensions of the composite material are smaller than those of the base material.

Preferably, the stainless steel billet is austenitic stainless steel.

Further, the stainless steel billet comprises the following chemical components in percentage by mass: c is less than or equal to 0.15%, si is less than or equal to 1.00%, mn is less than or equal to 2.00%, P is less than or equal to 0.045%, S is less than or equal to 0.030%, ni:6.0 to 22.0 percent, cr:16.0 to 26.0 percent, mo is less than or equal to 3.0 percent, and the balance is Fe and unavoidable impurities. The stainless steel billet with the chemical composition can further ensure the performance of the composite board, especially the corrosion resistance of the composite board under the condition of the technical effects, for example, the composite board obtained by the method (namely obtained by rolling the composite board) is boiled in sulfuric acid-copper sulfate solution for 20 hours, and after 180 DEG bending, no intergranular corrosion cracks exist.

The chemical components of the two stainless steel billets may be the same or different, and only one of the chemical components provided by the preferred scheme may be used, or both of the chemical components provided by the preferred scheme may be used or not used.

As a preferable scheme, the carbon steel billet comprises the following chemical components in percentage by mass: c:0.05 to 0.09 percent, si:0.14 to 0.22 percent, mn:1.41 to 1.49 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.0020 percent, cr:0.16 to 0.24 percent, ni:0.11 to 0.19 percent, mo:0.11 to 0.19 percent, nb: 0.021-0.029%, ti: 0.011-0.019%, al:0.030 to 0.040 percent, and the balance of Fe and unavoidable impurities. The carbon steel billet adopting the chemical composition can further improve the mechanical property of the composite board and ensure the toughness under the condition of the technical effects by combining the control of each temperature, time, rolling reduction and cooling speed in the rolling step of the composite board, for example, the impact energy of the composite board at 0 ℃ is more than or equal to 120J, the impact energy of the composite board at-20 ℃ is more than or equal to 120J, and the impact energy of the composite board at-40 ℃ is more than or equal to 120J; the composite board is bent outwards by 180 degrees without cracks, and bent inwards by 180 degrees without cracks.

Similar to the description of the stainless steel plate, the chemical compositions of the two carbon steel billets may be the same or different, and only one of the two carbon steel billets may or may not use the chemical composition provided by the preferred embodiment.

As a preferable scheme, the surface oxide skin pressing depth and the surface pit depth of the carbon steel billet are less than or equal to 0.3mm, and the unevenness is less than or equal to 3mm/m; the stainless steel billet has no scratch on the surface and the unevenness is less than or equal to 2mm/m. Thus, the steel billet is prevented from entering the production line of the composite board with obvious surface defects or plate defects.

Next, as for the step "surface-treating at least one surface of each of the two base materials and the two composite materials", that is, a blank surface-treating step. The present invention is provided with five preferred embodiments, which are described separately below.

< first embodiment of the blank surface treatment step >

In this embodiment, one surface of each base material and each composite material is polished to remove surface scale, exposing metallic luster.

Referring to fig. 1a, for example, polishing is performed on the surface p1a of the base material 11a by using a grinder, belt sander or milling machine to remove surface oxide skin and expose metallic luster; similarly, polishing is performed on the surface p2a of the prepared base material 12a by using a grinder, belt sander or milling machine to remove surface scale and expose metallic luster.

Grinding and polishing the surface p3a of the prepared composite material 21a by adopting a wire wheel to remove surface oxide skin and expose metallic luster; similarly, the surface p4a of the prepared composite material 22a is polished with a wire wheel to remove surface scale and expose metallic luster.

As will be seen later, when assembling, the surface treated (polished in this embodiment) is used as a surface where the base material and the composite material contact each other, for example, the surface p1a and the surface p3a contact each other, and the surface p4a and the surface p2a contact each other, whereby the interface bonding quality can be ensured.

< second embodiment of the blank surface treatment step >

In this embodiment, as in the first embodiment, one surface (e.g., surfaces p3b and p4b in fig. 1 b) of each composite material is polished to remove surface oxide skin and expose metallic luster, which is not described again.

In this embodiment, unlike the first embodiment, the surface treatment of the substrate is performed:

referring to fig. 1b, the surface p1b of the base material 11b is milled to process the surface p1b into a surface p1b0, the surface p1b0 being a laterally inclined surface having a length l11=l1 and a width W11 > W1, and accordingly, the base material 11b is processed into a non-uniform thickness billet having a thickness that is tapered in the lateral direction (i.e., in the width direction), that is, the base material 11b is milled to have a width direction with a side to side height that is gradually increased.

Similarly, the surface p2b of the base material 12b is subjected to milling processing to process the surface p2b into a surface p2b0, the surface p2b0 being a laterally inclined surface having a length l11=l1 and a width W11 > W1, and the base material 12b being correspondingly processed into a non-uniform thickness billet having a thickness that gradually varies in the lateral direction.

In the milling process of the surface p2b of the base material 12b and the surface p1b of the base material 11b, the surfaces are complementary to each other in terms of the relative shape, that is, the processed surface p2b0 and the surface p1b0 are complementary to each other in terms of the relative shape. For example, the lateral inclination angle of the surface p2b0 (for example, the angle with the original surface p2 b) is equal to the lateral inclination angle of the surface p1b0 (for example, the angle with the original surface p1 b), whereby the upper and lower surfaces of the composite blank can be ensured to be parallel at the time of subsequent assembly.

It will be appreciated that the surface oxide scale on the surface p1b of the base material 11b and the surface p2b of the base material 12b can be removed by the above-described milling process, and metallic luster is exposed.

As will be seen later, by using the surface treated (milled in this embodiment) as the surface where the base material and the composite material contact each other, for example, the surface p1b0 and the surface p3b contact each other, and the surface p4b and the surface p2b0 contact each other, the interface bonding quality can be ensured as in the first embodiment, and the embodiment can be further used for preparing non-uniform thickness composite boards with a gradual change in lateral thickness, so as to improve the application scene and range of the composite boards.

< third embodiment of the blank surface treatment step >

This embodiment is substantially the same as the aforementioned second embodiment (surface treatment including surfaces p3c and p4 c), except that: the thickness gradient of the substrate in the transverse direction in the second embodiment is changed to the thickness gradient of the substrate in the longitudinal direction (i.e., in the length direction) in the present embodiment. The following description of the distinguishing points refers to the second embodiment, and the other identical points will not be repeated.

Referring to fig. 1c, the surface p1c of the base material 11c is milled to process the surface p1c into a surface p1c0, the surface p1c0 being a longitudinally inclined surface having a length L11 > L1 and a width w11=w1, and correspondingly, the base material 11c is processed into a non-uniform thickness billet having a thickness gradient in the longitudinal direction.

Similarly, the surface p2c of the base material 12c is subjected to milling processing to process the surface p2c into a surface p2c0, the surface p2c0 being a longitudinally inclined surface having a length L11 > L1 and a width w11=w1, and the base material 12c is correspondingly processed into a non-uniform thickness billet having a thickness that is tapered in the longitudinal direction.

In the milling process of the surface p2c of the base material 12c and the surface p1c of the base material 11c, the surfaces are made complementary to each other in terms of the relative shape, that is, the processed surface p2c0 and the surface p1c0 are made complementary to each other in terms of the relative shape. For example, the longitudinal inclination angle of the surface p2c0 (for example, the angle with the original surface p2 c) is equal to the longitudinal inclination angle of the surface p1c0 (for example, the angle with the original surface p1 c), whereby the upper and lower surfaces of the composite blank can be ensured to be parallel at the time of subsequent assembly.

It will be appreciated that the surface oxide scale on the surface p1c of the base material 11c and the surface p2c of the base material 12c can be removed by the above-described milling process, and metallic luster is exposed.

< fourth embodiment of the blank surface treatment step >

In this embodiment, one surface of each substrate is milled, and the surface is processed into an irregular uneven surface including n planes connected in order in the lateral direction, and the substrate is a non-uniform thickness blank having a non-monotonically changing thickness in the lateral direction, and the length l12=l1 and the total width W12 > W1 of the irregular surface.

For example, referring to fig. 1d, the surface p1d of the substrate 11d is milled, the surface p1d is processed from the horizontal surface in fig. 1d (a) to an irregular concave-convex surface p1d0 shown in fig. 1d (B), the irregular concave-convex surface p1d0 specifically includes n planes sequentially connected in the transverse direction, where n is equal to 2, and in the drawing, 8 planes are exemplified, and as seen in the drawing, 1 st, 3 rd, 5 th, 7 th are all transverse inclined surfaces in the direction from the left to the right of the drawing, and 2 nd, 4 th, 6 th, 8 th are all horizontal surfaces, which is of course only an example, and it is also possible to variously implement n other numbers or include no horizontal surfaces but only transverse inclined surfaces, etc.

Referring to fig. 1d, the substrate 11d is processed into a non-uniform thickness blank having a non-monotonically varying thickness in the transverse direction by milling the surface p1 d.

The length l12=l1 of the irregular concave-convex surface p1d0, that is, is not changed by milling; while the total width W12 of the irregular concave-convex surface p1d0 is greater than W1, it is understood that the total width W12 is the sum of the widths of n planes.

Correspondingly, referring to fig. 1d, the surface p2d of the base material 12d is also milled, and the surface p2d is processed from the horizontal surface in fig. 1d (a) to an irregular concave-convex surface p2d0 shown in fig. 1d (B). When the surface p2d of the base material 12d and the surface p1d of the base material 11d are milled, the surfaces are complementary to each other in terms of the relative shape, that is, the processed surface p2d0 and the surface p1d0 are complementary to each other in terms of the relative shape.

The irregular concave-convex surface p2d0 also specifically includes n planes, in the example shown in the figure, which are connected in series in the lateral direction, in accordance with the relative shape complementation. The length l12=l1 of the irregular concave-convex surface p2d0, that is, is not changed by milling; while the total width W12 of the irregular concave-convex surface p2d0 is greater than W1, it is understood that the total width W12 is the sum of the widths of n planes of the irregular concave-convex surface p2d0.

Referring to fig. 1d, by milling the surface p2d, the base material 12d is processed into a non-uniform blank having a non-monotonically varying thickness in the lateral direction, and if the milled base materials 12d and 11d are placed opposite each other, the sum of the thicknesses of the two is constant, based on the relative shape complementation of the irregular concave-convex surface p2d0 and the irregular concave-convex surface p1d 0. Thus, in the subsequent assembly, the upper and lower surfaces of the composite blank are parallel.

The surface treatment of the two substrates in the present embodiment is described above, and the surface treatment of the two composite materials is described below.

In the present embodiment, the surface p3d of the prepared composite material 21d is polished by a wire wheel to remove surface oxide skin and expose metallic luster; similarly, the surface p4d of the prepared composite material 22d is polished with a wire wheel to remove surface scale and expose metallic luster.

And further, after the surface oxide skin is removed, each composite material is bent to match the surface shape of the base material 11d, 12d, so that each composite material matches the corresponding irregular concave-convex surface. For example, the composite material 21d is folded to be matched with the corresponding irregular concave-convex surface p1d0 so as to facilitate the bonding contact during the subsequent assembly; for another example, the composite material 22d is folded to match the corresponding irregular concave-convex surface p2d0, so that the contact is facilitated in the subsequent assembly.

The surface treatment of this embodiment, like the foregoing first embodiment, can ensure the quality of interface bonding, and can be further used to prepare non-uniform thickness composite boards with non-monotonic change in transverse thickness, so as to improve the applicable scene and range of the composite boards, enhance corrosion resistance compared with the existing steel boards, and avoid frequent welding and dissimilar welding between composite boards with different thicknesses.

< fifth embodiment of the blank surface treatment step >

This embodiment differs from the fourth embodiment described above in that: the change in thickness of the substrate in the transverse direction in the fourth embodiment is changed from the non-monotonic change in thickness of the substrate in the longitudinal direction in the present embodiment.

For example, referring to fig. 1e, the surface p1e of the base material 11e is milled, the surface p1e is processed from the horizontal surface in fig. 1e (a) to an irregular concave-convex surface p1e0 shown in fig. 1e (B), the irregular concave-convex surface p1e0 specifically includes n planes sequentially connected in the longitudinal direction, where n is equal to 2, and in the drawing, 8 planes are exemplified, and as seen in the drawing, 1 st, 3 rd, 5 th, 7 th are longitudinally inclined surfaces in the direction from the left to the right of the drawing, and 2 nd, 4 th, 6 th, 8 th are horizontal surfaces, which is of course only an example, and it is also possible to variously implement n other numbers or include no horizontal surfaces but only longitudinally inclined surfaces, etc.

Referring to fig. 1e, the substrate 11e is processed into a non-uniform thickness blank having a non-monotonically varying thickness in the longitudinal direction by milling the surface p1 e.

The width w12=w1 of the irregular concave-convex surface p1e0, that is, is not changed by milling; while the total length L12 of the irregular concave-convex surface p1e0 is greater than L1, it is understood that the total length L12 is the sum of the lengths of n planes.

Correspondingly, referring to fig. 1e, the surface p2e of the base material 12e is also milled, and the surface p2e is processed from the horizontal surface in fig. 1e (a) to an irregular concave-convex surface p2e0 shown in fig. 1e (B). When the surface p2e of the base material 12e and the surface p1e of the base material 11e are milled, the surfaces are complementary to each other in terms of the relative shapes, that is, the surfaces p2e0 and p1e0 after the milling are complementary to each other.

The irregular concave-convex surface p2e0 also specifically includes n planes, in the example shown in the figure, which are connected in series in the longitudinal direction, in accordance with the relative shape complementation. The irregular concave-convex surface p2e0 has a width w12=w1 and a total length L12 > L1.

Referring to fig. 1e, by milling the surface p2e, the base material 12e is processed into a non-uniform thickness blank having a non-monotonically varying thickness in the longitudinal direction, and the sum of the thicknesses of the two parts is constant if the milled base materials 12e and 11e are placed opposite to each other based on the relative shape complementation of the irregular concave-convex surface p2e0 and the irregular concave-convex surface p1e 0. Thus, in the subsequent assembly, the upper and lower surfaces of the composite blank are parallel.

In the present embodiment, the surface p3e of the prepared composite material 21e is polished by a wire wheel to remove surface oxide skin and expose metallic luster; similarly, the surface p4e of the prepared composite material 22e is polished with a wire wheel to remove surface scale and expose metallic luster.

And further, after the surface oxide skin is removed, each composite material is bent to match the surface shape of the base material 11e, 12e, so that each composite material matches the corresponding irregular concave-convex surface. For example, the composite material 21e is folded to be matched with the corresponding irregular concave-convex surface p1e0 so as to facilitate the bonding contact during the subsequent assembly; for another example, the composite material 22e is bent to match the corresponding irregular concave-convex surface p2e0, so that the contact is facilitated in the subsequent assembly.

The method and the device are the same as the fourth embodiment, the application scene and range of the composite board can be improved, the corrosion resistance is enhanced compared with the existing steel board, and frequent welding and dissimilar welding among the composite boards with different thicknesses are avoided.

While the above description has been made of five preferred embodiments of the sub-steps of the surface treatment of the ingot in the composite ingot preparing step, it should be noted that, although only the surface treatment of one surface of each of the substrate and the composite material is described, it should be noted that, regardless of the above five embodiments, the descaling treatment may be further performed on the other surfaces of each of the substrate and the composite material, and although such additional descaling treatment is not necessary but may be preferable to achieve the technical effects of the present invention; for example, in addition to the descaling of the surface of the substrate facing the side of the composite, the surface of the substrate facing away from the side of the composite (i.e., the surface of the composite plate) may be descaled.

The description of the other sub-steps of the composite blank preparation step is continued below.

The step of "painting a release agent on one surface of a piece of composite material", that is, the step of painting a release agent.

In the previous blank surface treatment step, the surface of the composite material, which is in contact with the base material during assembly, is subjected to surface treatment such as polishing, so as to ensure the interface bonding quality of the composite board; the purpose of the step of brushing the release agent is to avoid the release agent, so that the composite material and the surface contacted when the composite material are assembled are combined in the rolling step of the composite blank, and finally are difficult to separate.

Based on this, a release agent is optionally applied to one of the two composites. If the selected composite material is surface treated in the previous blank surface treatment step and the other is not surface treated, the release agent is applied to the surface which is not surface treated in the release agent application step. If, as mentioned above, both surfaces of the selected composite are surface treated in the previous blank surface treatment step, then in the release agent application step, the release agent is applied to the surface intended to be faced with the other composite at the time of assembly.

For example, taking fig. 1a as an example, a release agent may be applied to the surface p6a of the composite 22a or the surface p5a of the composite 21 a.

With respect to the release agent, two preferred embodiments are provided herein, each of which is described below.

< first embodiment of the Release agent >

In this embodiment, the release agent is a coating solution containing silicon oxide and magnesium oxide, wherein the mass ratio of silicon oxide to magnesium oxide is 3:1. The isolating agent of the embodiment can achieve good isolating effect and ensure the subsequent separation of two composite board small plates.

The preparation method of the release agent comprises the following steps: the method comprises the following steps of mixing release agent powder, binder powder and water according to a mass ratio of 27:3:70, mixing to obtain the fluid release agent coating liquid. Wherein the isolating agent powder is silicon oxide and magnesium oxide, and the mass ratio is 3: 1. The binder powder is polyvinyl alcohol and thermosetting phenolic resin, and the mass ratio is 1: 1.

When the release agent is adopted to paint the surface of the composite material, the amount of the paint release agent is 20ymg/m ² That is, the weight of the release agent per unit area of the surface of the composite material was 20ymg. Wherein y is the ratio of the thickness of the composite billet produced in the composite billet preparation step to the thickness of the composite plate large plate formed by subsequent rolling, and the ratio is also called a composite billet rolling compression ratio.

Further, according to the present embodiment, after finishing the application of the release agent and before the subsequent assembly, the composite material coated with the release agent is placed in a bogie hearth furnace to be heated and dried, the drying temperature is 340-360 ℃, and the drying time is 35-45 min.

< second embodiment of Release agent >

In this embodiment, the components of the release agent are as follows by weight: 25-35% of silicon nitride, 5-10% of thermosetting amino resin and 55-70% of water. Compared with the existing isolating agent and even compared with the first embodiment of the isolating agent, the isolating agent of the embodiment not only can achieve good isolating effect and ensure the subsequent separation of two composite board small plates, but also has strong chemical stability, high temperature resistance and thermal shock resistance of the active ingredient silicon nitride, and the thermosetting amino resin serving as the binder can be cured at low temperature, has no toxicity and can achieve stronger bonding effect with little consumption, thus the isolating agent is low in cost as a whole, simple to operate and good in isolating and attaching effects.

Here, there is provided a preferred preparation method of the release agent, comprising: firstly, placing 5-10% of silicon nitride (in percentage by weight) into a container such as a beaker, and then pouring 15-25% of water for stirring; after the silicon nitride has no granular feel and no bubble, pouring 2-3% of thermosetting amino resin, and continuing stirring; when the mixture is in a viscous state, continuously pouring the residual silicon nitride and water, stirring for 3-5 min, and pouring the residual thermosetting amino resin; and (5) stirring to be sticky, and preparing the release agent.

When the release agent is adopted to paint the surface of the composite material, the thickness of the paint release agent is 0.2-0.5 mm.

Further, according to the present embodiment, after finishing the application of the release agent and before the subsequent assembly, the composite material coated with the release agent is heated and dried at 100 to 250 ℃ for 20 to 40 minutes.

Next, after the step of applying the release agent, the step of "assembling in the order of stacking the base material, the composite material, and the base material" will be described.

The step of assembling is carried out according to the stacking sequence of the base material, the composite material and the base material, namely the assembling step. Wherein, in addition to the stacking sequence of the base material, the composite material and the base material, the following needs to be satisfied:

1) The surfaces of the base material and the composite material which are contacted with each other are the surfaces subjected to the surface treatment; for example, in the first embodiment of the blank surface treatment step described above, referring to fig. 2a, the surface p2a of the substrate 12a and the surface p4a of the composite material 22a are in contact with each other, and the surface p1a of the substrate 11a and the surface p3a of the composite material 21a are in contact with each other; in the second embodiment of the blank surface treatment step described hereinbefore, with reference to fig. 2b, the surface p1b0 and the surface p3b are in contact with each other, and the surface p4b and the surface p2b0 are in contact with each other; in the third embodiment of the blank surface treatment step described above, referring to fig. 2c, the surface p1c of the substrate 11c and the surface p3c of the composite material 21c are in contact with each other, and the surface p2c of the substrate 12c and the surface p4c of the composite material 22c are in contact with each other; in the fourth embodiment of the blank surface treatment step described above, referring to fig. 2d, the irregular concave-convex surface p1d0 and the surface p3d of the composite material 21d are in contact with each other, and the irregular concave-convex surface p2d0 and the surface p4d of the composite material 22d are in contact with each other; in the fifth embodiment of the blank surface treatment step described above, referring to fig. 2e, the irregular concave-convex surface p1e0 and the surface p3e of the composite material 21e are in contact with each other, and the irregular concave-convex surface p2e0 and the surface p4e of the composite material 22e are in contact with each other;

2) The surface coated with the release agent faces the other composite material; for example, referring to fig. 2a, one of the surface p6a and the surface p5a is coated with a release agent 30a; referring to fig. 2b, one of the surface p6b and the surface p5b is coated with a release agent 30b; referring to fig. 2c, one of the surface p6c and the surface p5c is coated with a release agent 30c; referring to fig. 2d, one of the surface p6d and the surface p5d is coated with a release agent 30d; referring to fig. 2e, one of the surfaces p6e and p5e is coated with a release agent 30e;

3) The composite material is placed in the middle relative to the base material; in this regard, the foregoing describes that the length-width dimensions of the composite material are smaller than the length-width dimensions of the base material, L2 is smaller than L1, W2 is smaller than W1, and when the composite material is assembled, the distances from the two lateral sides of the composite material to the corresponding two lateral sides of the base material are equal, and the distances from the two longitudinal sides of the composite material to the corresponding two lateral sides of the base material are also equal.

The following describes the blank surface treatment step in the fifth embodiment at point 3. Since the composite material is disposed substantially vertically symmetrically, only a group of the base material and the composite material in the composite material will be described as an example, for example, the upper group.

For the first embodiment of the blank surface treatment step described above, referring to fig. 2a, the length L1, width W1 of the surface p1a of the substrate 11a, the length L2, width W2, l2=l1-L0, w2=w1-W0, and the preferred value ranges of L0 and W0 are 90 to 150mm, respectively; in the assembled state, the distance from the lateral side (corresponding to the long side of the surface p3 a) of the composite material 21a to the lateral side (corresponding to the long side of the surface p1 a) of the base material 11a is half of W0, and the distance from the longitudinal side (corresponding to the short side of the surface p3 a) of the composite material 21a to the longitudinal side (corresponding to the short side of the surface p1 a) of the base material 11a is half of L0.

For the second embodiment of the blank surface treatment step described above, referring to fig. 2b, the length L11, width W11 of the surface p1b0 of the substrate 11b, the length L2, width W2, l2=l11-L0, w2=w11-W0 of the surface p3b of the composite material 21b are preferably in the range of 90 to 150mm, respectively; in the assembled state, the distance from the lateral side (corresponding to the long side of the surface p3 b) of the composite material 21b to the lateral side (corresponding to the long side of the surface p1b 0) of the base material 11b is half of W0, and the distance from the longitudinal side (corresponding to the short side of the surface p3 b) of the composite material 21b to the longitudinal side (corresponding to the short side of the surface p1b 0) of the base material 11b is half of L0.

For the third embodiment of the blank surface treatment step described above, referring to fig. 2c, the preferred values of the length L11, width W11 of the surface p1c0 of the substrate 11c, the length L2, width W2 of the surface p3c of the composite 21c, l2=l11-L0, w2=w11-W0, L0 and W0 are respectively 90 to 150mm; in the assembled state, the distance from the lateral side (corresponding to the long side of the surface p3 c) of the composite material 21c to the lateral side (corresponding to the long side of the surface p1c 0) of the base material 11c is half of W0, and the distance from the longitudinal side (corresponding to the short side of the surface p3 c) of the composite material 21c to the longitudinal side (corresponding to the short side of the surface p1c 0) of the base material 11c is half of L0.

For the fourth embodiment of the blank surface treatment step described above, referring to fig. 2d, the length L12 and width W12 of the irregular concave-convex surface p1d0 of the substrate 11d, and the length L2 and width W2 of the surface p3d of the composite material 21d, l2=l12-L0, w2=w12-W0, and the preferred value ranges of L0 and W0 are 90 to 150mm, respectively; in the assembled state, the distance from the side edge in the widthwise direction of the composite material 21d (corresponding to the long side of the surface p3 d) to the side edge in the widthwise direction of the base material 11d (corresponding to the long side of the irregular concave-convex surface p1d 0) is half of W0, and the distance from the side edge in the longitudinal direction of the composite material 21d (corresponding to the short side of the surface p3 d) to the side edge in the longitudinal direction of the base material 11d (corresponding to the short side of the irregular concave-convex surface p1d 0) is half of L0.

For the fifth embodiment of the blank surface treatment step described above, referring to fig. 2e, the length L12 and width W12 of the irregular concave-convex surface p1e0 of the substrate 11e, and the length L2 and width W2 of the surface p3e of the composite material 21e, l2=l12-L0, w2=w12-W0, and the preferred value ranges of L0 and W0 are 90 to 150mm, respectively; in the assembled state, the distance from the side edge in the widthwise direction of the composite material 21e (corresponding to the long side of the surface p3 e) to the side edge in the widthwise direction of the base material 11e (corresponding to the long side of the irregular concave-convex surface p1e 0) is half of W0, and the distance from the side edge in the longitudinal direction of the composite material 21e (corresponding to the short side of the surface p3 e) to the side edge in the longitudinal direction of the base material 11e (corresponding to the short side of the irregular concave-convex surface p1e 0) is half of L0.

In the above description of the assembling step, in a preferred embodiment, after the assembling step is performed, the stacked four billets are integrally placed under a four-column hydraulic machine, and the opposite surfaces of the two base materials (i.e., the upper surface of the upper base material and the lower surface of the lower base material) are pressurized, where the pressure is not less than 500 tons. Thus, contact between adjacent billets can be made tighter.

Further, in the step of preparing four seals with the width W3, the seals are attached to four sides of two composite materials, and gas shielded welding is carried out between the adjacent seals and between the seals and the base materials, so that two base materials and the seals form a whole to obtain a composite blank base blank, and the four stacked steel blanks form a whole to be connected into the composite blank base blank based on the arrangement of the seals. Specifically, the composite blank base stock is: the two base materials form an upper surface and a lower surface, the two composite materials are positioned in the middle, four seals are enclosed around the two composite materials in a four-sided frame, and the two base materials are connected. In fig. 2 a-2 e, the seals are designated 40a, 40b, 40c, 40d and 40e, respectively.

The width W3=2T2-1-2 mm of the seal, namely the width of the seal is slightly smaller than the sum of the thicknesses of the two composite materials by 1-2 mm. The upper and lower composite materials are wrapped by the seal with the width, so that the wrapping effect is improved.

In the four seals, two seals are respectively attached to two lateral side edges of two composite materials, and the length L31=L2-1-2 mm; the other two seals are respectively attached to two longitudinal side edges of the two composite materials, and the length L32=W2-1-2 mm.

Preferably, the thickness T3 of the seal is 12-15 mm.

The forming mode of each seal may be directly cut out of one steel plate according to the thickness T3, the width W3, the length L31 or the length L32 without welding, or may be formed by splicing a plurality of seals of different lengths by welding, for example, the seal at both side edges in the longitudinal direction of the two composite materials in the fourth embodiment of the blank surface treatment step described above, and the seal at both side edges in the transverse direction of the two composite materials in the fifth embodiment of the blank surface treatment step described above.

Further, the seal adopts the same steel grade as the base material, and is better, the seal is made of the same material as the base material, and the seal comprises the following chemical components in percentage by mass: c:0.05 to 0.09 percent, si:0.14 to 0.22 percent, mn:1.41 to 1.49 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.0020 percent, cr:0.16 to 0.24 percent, ni:0.11 to 0.19 percent, mo:0.11 to 0.19 percent, nb: 0.021-0.029%, ti: 0.011-0.019%, al:0.030 to 0.040 percent, and the balance of Fe and unavoidable impurities.

In a preferred embodiment, the step is performed by preheating with a baking gun or electrothermal cotton, etc. at a temperature of 100-150 ℃ before the gas shielded welding between the adjacent seals and between the seals and the substrate. Further, the two ends and two sides of each seal can be polished firstly to remove surface oxide skin, so that the welding effect is improved; and/or grooves can be formed at two ends and two sides of each seal.

Further, as a preferred embodiment, in the step of performing gas shielded welding between adjacent seals and between the seal and the base material, the welding current is 260-290A, the welding voltage is 24-28V, the welding speed is 300-360 mm/min, and the temperature between the welding process control channels is 135-165 ℃.

Alternatively, in gas shielded welding, the welding wire is GML-W60, the diameter of the welding wire is 1.2mm, and the shielding gas is 75-80% Ar+20-25% CO by volume percent ₂ 。

Next, for the step of processing a round hole on the seal at the groove on the side edge of the composite blank base blank, and welding a seamless steel tube at the round hole, wherein the groove is formed between two base materials and outside the seal; in this step, a round hole is machined to weld the seamless steel pipe so as to facilitate the subsequent evacuation of the interior of the composite blank.

As a preferred mode, the round hole is formed in the middle of the short side (i.e., the side in the longitudinal direction) of the composite green body, but is not limited thereto.

As a preferable mode, the diameter of the round hole is 8-12 mm; correspondingly, the outer diameter of the seamless steel pipe is consistent with the diameter of the round hole, the wall thickness is 1.2-2 mm, and the length is 200-400 mm.

And then, carrying out overlaying welding on grooves on four sides of the composite blank base blank in the step, and specifically adopting submerged arc overlaying welding. Alternatively, the submerged arc welding wire is GWL-WCJQ1, the submerged arc welding flux is GXL-105Q, and the diameter of the welding wire is 4.0mm. It will be appreciated that outside the four-sided frame formed by the seal, a four-sided frame shaped filling layer is formed by butt welding in this step, see fig. 2 a-2 e, wherein the filling layers formed by the weld deposit are denoted 50a, 50b, 50c, 50d and 50e, respectively.

As a preferred mode, before welding, the welding flux is baked for 2 hours at 350 ℃ and then is kept at 150 ℃ for 1 hour; in the welding process, the temperature between control channels is 135-165 ℃, the welding current is 570-630A, the welding voltage is 28-32V, and the welding speed is 420-480 mm/min. Therefore, the submerged arc surfacing technology combines the sealing strip wrapping and gas shielded welding to jointly realize the stable connection of four billets, ensures the connection strength, avoids cracking abnormality in the subsequent composite billet rolling step, and further can further improve the interface bonding effect on the basis of realizing the quality advantage of the composite plate.

In addition, in the welding process, before each welding construction, welding bead attachments need to be cleaned, and welding beads are kept clean; and after welding, covering with heat-insulating cotton to insulate heat.

Next, the step of "vacuum pumping the composite blank through the seamless steel pipe by using a vacuum pump, the vacuum degree

≤10 ^-1 Pa, and then maintaining the pressure for more than 4 hours; finally, in the sealing treatment of the seamless steel tube, the air suction port of the vacuum pump is abutted with the seamless steel tube, and the seamless steel tube is communicated with the space inside the composite blank (such as the surface gap between the composite material and the base material, the surface gap between the composite material and the composite material, the surface gap between the composite material and the seal, and the like) so as to discharge the air in the space until the vacuum degree is less than or equal to 10 ^-1 Pa, and the vacuum degree can be ensured by maintaining the pressure for more than 4 hours. Therefore, air in the space can be avoided, and surface oxidation at the composite interface is caused in the subsequent rolling of the composite blank, so that the bonding quality of the composite interface is ensured.

Further, in this step, the seamless steel pipe is subjected to a sealing treatment, which can be performed in a manner that is currently available in the steel field, for example, by heating the seamless steel pipe with a flame gun and flattening the pipe to effect sealing.

The above description is made in detail on the total steps of the preparation of the composite billet, and the preparation method of the present invention further includes the total steps of rolling the composite billet after the total steps of the preparation of the composite billet, as described above. Specifically, the total step of rolling the composite billet comprises the following sub-steps:

and directly feeding the large composite board leaving the ultra-rapid cooling system into a straightener for straightening.

In the total rolling step of the composite blank, parameters such as heating temperature, heating time, heat preservation time, various temperatures in rolling, rolling reduction, temperature in cooling, cooling speed and the like are controlled, so that the structure of the finally obtained composite plate is a bainite+ferrite structure, excellent mechanical properties including yield strength of more than or equal to 420MPa, tensile strength of more than or equal to 540MPa, elongation after break of more than or equal to 18%, yield ratio of less than or equal to 0.85 can be ensured, and excellent surface quality, plate shape and interface bonding quality can be obtained. Particularly in combination with the chemical composition of the carbon steel sheet as described hereinbefore, a significant further improvement in mechanical properties is achieved.

In the total rolling step of the composite blank, the step of straightening the large composite plate directly into a straightener after leaving the ultra-fast cooling system is performed, wherein the straightening is warm straightening, and the large composite plate is straightened directly at the temperature basically consistent with or slightly lower than the final cooling temperature after leaving the ultra-fast cooling system at the final cooling temperature of 510-530 ℃ so as to ensure the flatness of the large composite plate.

As a preferred implementation mode of the total rolling step of the composite blank, referring to FIG. 3a, after the warm straightening is carried out for 1-3 times, a cooling bed on a large composite plate is naturally cooled, and when the surface temperature is reduced to below 200 ℃, a cold straightening machine is adopted for cold straightening. Thus, the plate shape of the finally obtained composite plate can be improved.

As still another preferred embodiment of the total rolling step of the composite blank, referring to fig. 3b, after the warm straightening is performed for 1-3 times, the composite plate is placed between two steel plates with the temperature of Tf-50-Tf for stack cooling, the stack cooling time is 0.4min/mm×t0±5min, and t0 is the thickness of the composite plate, so that the composite plate can be slowly cooled in the stack cooling time and can be clamped by the steel plates to maintain the uniformity of the temperature of the core surface; and naturally cooling the cooling bed on the large composite board to room temperature after the cooling is finished. Wherein, the liquid crystal display device comprises a liquid crystal display device,

T _f ＝550+30[Si]-20[Mn]+15[Cr]-15[Ni]+10[Mo]Wherein [ Si ]]、[Mn]、[Mo]、[Cr]、[Ni]Is 100 times of the mass percent of each element in the base material. According to the preferred embodiment, the structure, the performance and the shape of the finally obtained composite board can be further greatly improved by the stack cooling, particularly the temperature and the stack cooling time of two steel plates in the stack cooling.

The total step of rolling the composite blank is described in detail above, and the preparation method of the invention further comprises the total step of separating and straightening the composite plate as described above. Specifically, the total step of separating and straightening the composite board comprises the following sub-steps:

for the large composite board obtained in the previous composite blank rolling total step, a plasma cutting machine is adopted to cut four sides of the large composite board to remove parts outside sealing strips, and the large composite board is separated into an upper composite board small board and a lower composite board small board;

Wherein, regarding the part other than the seal in the step of cutting the four sides thereof to remove the part other than the seal, namely, the edge part on the large plate of the composite plate converted from the seal and the filling layer in the composite blank mentioned above after the previous rolling step of the composite blank. Thus, the part is removed to expose the stainless steel cladding, and the large composite plate is separated into an upper composite plate small plate and a lower composite plate small plate without the connecting function of the part. Referring to fig. 4 a-4 e, corresponding to the five embodiments of the blank surface treatment steps described previously, fig. 4 a-4 e show the cross-sectional shape of two corresponding composite panel platelets (i.e., the final composite panel), respectively.

Each composite plate is composed of a composite layer and a base layer, wherein the composite layer is obtained by rolling an original composite material, the base layer is obtained by rolling an original base material, and in view of the fact, in fig. 4 a-4 e, the composite layer is still marked with the label of the original composite material, and the base layer is also marked with the label of the original base material.

Compared with the prior art, the invention has the beneficial effects that: the composite board prepared by the preparation method has the advantages of excellent surface quality, excellent board shape, excellent interface bonding and the like, for example, obvious surface defects such as pits, side scratches and the like of the existing composite board are avoided, for example, the unevenness of the composite board is less than or equal to 3mm/m, the bonding rate of the composite interface of the composite board is 100%, the shearing strength is more than or equal to 300MPa, the design of chemical components is combined, the total thickness of the composite board is 5-55 mm, the thickness of a base layer is 4-45 mm, the thickness of a cladding layer is 1-10 mm, the structure is ferrite+bainitic structure, the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after fracture is more than or equal to 18%, and the yield ratio is less than or equal to 0.85; in addition, the impact energy at 0 ℃ is more than or equal to 120J, the impact energy at minus 20 ℃ is more than or equal to 120J, and the impact energy at minus 40 ℃ is more than or equal to 120J; the composite board is bent outwards by 180 degrees without cracks, and bent inwards by 180 degrees without cracks; boiling in sulfuric acid-copper sulfate solution for 20h, and bending at 180 degrees to obtain the composite layer without intergranular corrosion crack.

The above detailed description is merely illustrative of possible embodiments of the present invention, which should not be construed as limiting the scope of the invention, and all equivalent embodiments or modifications that do not depart from the spirit of the invention are intended to be included in the scope of the invention.

The advantages of the invention will be further illustrated by the following examples, which are, of course, only some, but not all of the many variations encompassed by the invention.

In these examples, the steel grade/chemical composition of the selected composite and substrate materials are shown in table 1, respectively.

TABLE 1

In this case, the composite blank was prepared according to the embodiment of the present invention, and the substrate, composite material, thickness of the composite blank, and type of the composite blank are shown in table 2. Wherein the substrate thickness type is "constant thickness" corresponding to the first embodiment of the blank surface treatment step, and the substrate thickness type is "variable thickness" corresponding to any one of the second to fifth embodiments of the blank surface treatment step.

TABLE 2

Further, for each example, the clad-blank rolling step provided according to an embodiment of the present invention was performed, and specific parameters in the clad-blank rolling are shown in table 3. Wherein in the list of the stack cooling temperatures in Table 3, "-" indicates that the cooling bed on the large plate of the composite plate after straightening is naturally cooled according to the method of cold straightening by a cold straightener when the surface temperature is reduced to below 200 ℃ in the implementation process The implementation, while the stack cooling temperatures are shown in a column with numbers, indicates that the implementation is performed by placing the straightened composite board at a temperature T according to the description _f -50℃～T _f Is implemented by a mode of cold stacking between two steel plates.

TABLE 3 Table 3

Further, the total thickness of the composite board large plate and the thickness of the composite board small plate (i.e., the composite board finished product) prepared in each example are shown in Table 4. The composite blanks corresponding to examples 2, 4, 6 and 8 are base materials with variable thicknesses, and the thicknesses of the corresponding composite boards and the base layers are all in a thickness range (namely, the minimum thickness to the maximum thickness) instead of the fixed values.

TABLE 4 Table 4

Further, the composite board of each example was sampled and tested, the interfacial bonding ratio of each example was 100%, the inward bend was 180 ° acceptable (no crack), the outward bend was 180 ° acceptable (no crack), and after boiling in sulfuric acid-copper sulfate solution for 20h, the composite layer was free of intergranular corrosion cracking after 180 ° bending. In addition, other performance test results are shown in table 5.

TABLE 5

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Claims

1. The 420 MPa-grade stainless steel composite board is characterized in that the chemical components of a base layer of the composite board are as follows in percentage by mass: c:0.05 to 0.09 percent, si:0.14 to 0.22 percent, mn:1.41 to 1.49 percent, P is less than or equal to 0.012 percent, S is less than or equal to 0.0020 percent, cr:0.16 to 0.24 percent, ni:0.11 to 0.19 percent, mo:0.11 to 0.19 percent, nb: 0.021-0.029%, ti: 0.011-0.019%, al:0.030 to 0.040 percent, and the balance of Fe and unavoidable impurities; the yield strength of the composite board is more than or equal to 420MPa, the tensile strength is more than or equal to 540MPa, the elongation after fracture is more than or equal to 18%, and the yield ratio is less than or equal to 0.85; the composite interface bonding rate of the composite board is 100%, the shearing strength is more than or equal to 300MPa, and the unevenness is less than or equal to 3mm/m.

2. The 420 MPa-grade stainless steel composite plate according to claim 1, wherein the total thickness is 5-55 mm, the thickness of the base layer is 4-45 mm, the thickness of the clad layer is 1-10 mm, and the structure is a bainitic+ferritic structure.

3. The 420 MPa-grade stainless steel composite panel according to claim 1, wherein the composite panel comprises the chemical components in mass percent: c is less than or equal to 0.15%, si is less than or equal to 1.00%, mn is less than or equal to 2.00%, P is less than or equal to 0.045%, S is less than or equal to 0.030%, ni:6.0 to 22.0 percent, cr:16.0 to 26.0 percent, mo is less than or equal to 3.0 percent, and the balance is Fe and unavoidable impurities.

4. The 420 MPa-grade stainless steel composite plate according to claim 1, wherein the composite plate has an impact energy of not less than 120J at 0 ℃, an impact energy of not less than 120J at-20 ℃, and an impact energy of not less than 120J at-40 ℃; the composite board is bent outwards by 180 degrees without cracks, and bent inwards by 180 degrees without cracks; boiling in sulfuric acid-copper sulfate solution for 20h, and bending at 180 degrees to obtain the composite layer without intergranular corrosion crack.

5. A method for preparing the 420 MPa-grade stainless steel composite board according to any one of claims 1 to 4, comprising the steps of:

1) Preparation of composite blank

coating a release agent on one surface of a composite material;

overlaying the grooves on the four sides of the composite blank base blank;

2) Rolling of composite billets

3) Composite board separation straightening

6. The method of manufacturing a 420 MPa-grade stainless steel composite panel according to claim 5, wherein the step of surface-treating at least one surface of each of the two base materials and the two composite materials comprises:

7. The method of manufacturing a 420 MPa-grade stainless steel composite panel according to claim 5, wherein the step of surface-treating at least one surface of each of the two base materials and the two composite materials comprises:

8. The method of manufacturing a 420 MPa-grade stainless steel composite panel according to claim 5, wherein the step of surface-treating at least one surface of each of the two base materials and the two composite materials comprises: and polishing one surface of each base material and each composite material to remove surface oxide skin.

9. The method according to any one of claims 6 to 8, wherein in the step of centering the composite material with respect to the base material, the distance from the lateral side of the composite material to the corresponding side of the base material is half of the difference in width between the composite material and the base material, and the distance from the longitudinal side of the composite material to the corresponding side of the base material is half of the difference in length between the composite material and the base material.

10. The method for preparing the 420MPa grade stainless steel composite plate according to claim 5, wherein after the step of directly straightening the large composite plate which leaves the ultra-rapid cooling system and enters the straightener, the straightened large composite plate is naturally cooled by a cooling bed, and when the surface temperature is reduced to below 200 ℃, the large composite plate is subjected to cold straightening by a cold straightener.

11. The method for preparing the 420MPa grade stainless steel composite plate according to claim 5, wherein the step of directly entering a straightener for straightening after the large composite plate leaves an ultra-rapid cooling system is as follows:

Placing the straightened composite board large board at the temperature T _f -50℃～T _f Performing stack cooling between two steel plates, wherein the stack cooling time is 0.4min/mm multiplied by 0+/-5 min, and t0 is the thickness of a large composite plate;

12. The method for manufacturing a 420 MPa-grade stainless steel composite plate according to claim 5, wherein in the step of "overlaying grooves on four sides of the composite base blank", submerged arc overlaying is adopted;

13. The method for manufacturing a 420 MPa-grade stainless steel composite plate according to claim 5, wherein in the step of performing gas shielded welding between adjacent seals and between the seal and the base material, the welding current is 260-290A, the welding voltage is 24-28V, the welding speed is 300-360 mm/min, and the temperature between the welding process control channels is 135-165 ℃.