CN110527929B - Boron-containing stainless steel thick plate with excellent plasticity and toughness and preparation method thereof - Google Patents

Boron-containing stainless steel thick plate with excellent plasticity and toughness and preparation method thereof Download PDF

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CN110527929B
CN110527929B CN201910773871.XA CN201910773871A CN110527929B CN 110527929 B CN110527929 B CN 110527929B CN 201910773871 A CN201910773871 A CN 201910773871A CN 110527929 B CN110527929 B CN 110527929B
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CN110527929A (en
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刘海涛
李永旺
王昭杰
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Northeastern University China
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

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Abstract

A boron-containing stainless steel thick plate with excellent plasticity and toughness and a preparation method thereof are disclosed, wherein the components comprise, by mass, 18.0-20.0% of Cr, 12.0-15.0% of Ni, 0.2-2.0% of Mn, 0.5-1.5% of B, less than 0.5% of Si, less than 0.02% of C and the balance of Fe; the thickness is 20-80 mm, the tensile strength is more than or equal to 550MPa, the room-temperature elongation is more than or equal to 18 percent, and the room-temperature impact toughness is more than or equal to 200KJ/m2(ii) a The method comprises the following steps: (1) smelting molten steel; (2) carrying out rough rolling after soaking and heat preservation on the casting blank; (3) the rough rolling blank is provided with a V-shaped groove to be made into a single body; stacking a plurality of monomers, and performing vacuum welding; (4) welding common carbon steel plates at the front end and the rear end of the composite blank; (5) heating to 1100-1150 ℃, and carrying out multi-pass hot rolling; (6) cutting the end of plain carbon steel, carrying out solution treatment, and cooling in air to room temperature. The method of the invention realizes the homogenization and fine control of boride in the finished plate, and improves the plate shape and edge crack degree of the boron-containing stainless steel thick plate; the process production flow is compact, and the mechanization and automation are convenient to realize.

Description

Boron-containing stainless steel thick plate with excellent plasticity and toughness and preparation method thereof
Technical Field
The invention belongs to the technical field of metallurgical materials, and particularly relates to a boron-containing stainless steel thick plate with excellent plasticity and toughness and a preparation method thereof.
Background
As an electric energy with zero emission of carbon, the development of nuclear power is being regarded by various countries all over the world; during the storage and transportation of the spent fuel, thermal neutron shielding materials are required to reduce the reactivity of the spent fuel and prevent the spent fuel from returning to nuclear criticality. Among natural boron elements10The B isotope is effective in absorbing thermal neutrons, and then only produces soft gamma photons and readily absorbable alpha particles. The boron element is added into the stainless steel, so that the boron-containing stainless steel with excellent mechanical and corrosion resistance is prepared, and the boron-containing stainless steel is widely applied to the field of nuclear power. Different service environments and conditions such as post-treatment, storage and transportation of the spent fuel have different requirements on boron content, thick plates and performance of the boron-containing stainless steel.
After the boron element is added into the stainless steel, a large amount of hard and brittle eutectic borides are precipitated from the steel and are continuously distributed around austenite, so that not only is the hot workability of the blank deteriorated, but also the room-temperature mechanical properties, particularly the plasticity and the toughness of the finished plate are rapidly reduced. If the thickness of the prepared cast slab is increased, the nonuniformity of the size and distribution of the solidification structure is remarkably increased. In the subsequent rolling process, the uneven transmission of the rolling force from the surface of the rolled piece to the central area causes that the grains and components of the finished plate in the full thickness direction are difficult to achieve higher uniformity, and the mechanical property of the final finished plate is difficult to meet the requirement of service in the nuclear power field.
As the main method for preparing the high-boron stainless steel plate at present, the powder metallurgy method has unique technical advantages in preparing the boron-containing stainless steel thin plate, but for the boron-containing stainless steel thick plate, the sintering forming difficulty is high, the yield is low, the preparation period is long, and the preparation cost is expensive.
Disclosure of Invention
Aiming at the performance characteristics of the boron-containing steel thick plate and the problems of the preparation technology, the invention provides the boron-containing stainless steel thick plate with excellent plasticity and toughness and the preparation method thereof.
The boron-containing stainless steel thick plate with excellent plasticity and toughness comprises, by mass, 18.0-20.0% of Cr, 12.0-15.0% of Ni, 0.2-2.0% of Mn, 0.5-1.5% of B, less than 0.5% of Si, less than 0.02% of C, and the balance of Fe and inevitable impurity elements; the thickness of the material is 20-80 mm, the tensile strength is more than or equal to 550MPa, the room-temperature elongation is more than or equal to 18%, and the room-temperature impact toughness is more than or equal to 200KJ/m2。
In the boron-containing stainless steel thick plate with excellent plasticity and toughness, the boride with the grain diameter of less than or equal to 3.0 mu m in the structure accounts for more than 20 percent of the total mass of all the boride, and the boride with the grain diameter of more than or equal to 15.0 mu m accounts for less than 5 percent of the total mass of all the boride.
The preparation method of the boron-containing stainless steel thick plate with excellent plasticity and toughness provided by the invention comprises the following steps:
(1) smelting molten steel, and then preparing the molten steel into a boron-containing stainless steel casting blank through die casting or continuous casting; the thickness of the boron-containing stainless steel casting blank is 100-250 mm, and the boron-containing stainless steel casting blank comprises 18.0-20.0% of Cr, 12.0-15.0% of Ni, 0.2-2.0% of Mn, 0.5-1.5% of B, less than or equal to 0.5% of Si, less than or equal to 0.02% of C, and the balance of Fe and inevitable impurity elements by mass percent;
(2) heating the boron-containing stainless steel cast blank in a heating furnace along with the furnace to a soaking temperature T, preserving heat for 90-150 min, and then carrying out multi-pass rough rolling, wherein the final rolling temperature of the rough rolling is 900-1000 ℃, and the reduction delta h of each pass1The delta h less than or equal to 10mm is satisfied1≤H1mm, obtaining a rough rolling blank with the thickness of 30-80 mm;
the soaking temperature T is calculated according to the following formula:
T＝(1155－1450×b)℃ (1)；
calculate H1The formula is as follows:
H1＝0.065×Th－1500×b－20 (2)；
in the formulae (1) and (2), ThThe initial rolling temperature of each pass is unit ℃; b is the mass percent of boron element in the boron-containing stainless steel casting blank, unit percent;
(3) milling the rough rolling blank, forming a V-shaped groove for welding on the outer edge of the top surface and/or the bottom surface, and performing oil removal and drying treatment to prepare a composite blank monomer; stacking and aligning 2-3 composite blank monomers with the same size up and down, enabling V-shaped grooves formed in two adjacent composite blank monomers to be opposite, and then welding the two adjacent composite blank monomers at the V-shaped grooves under the vacuum condition that the vacuum degree is less than or equal to 2.0Pa to prepare a composite blank;
(4) welding and fixing end faces of front and rear ends of the composite blank with the end face of a common carbon steel plate respectively, wherein the width of the common carbon steel plate is the same as that of the composite blank, and the thickness of the common carbon steel plate is the same as that of the composite blank to prepare a combined blank;
(5) heating the combined blank to 1100-1150 ℃, preserving heat for 60-150 min, and then carrying out multi-pass hot rolling, wherein the final rolling temperature is 900-1000 ℃, and the reduction delta h of each pass2Satisfies the requirement of less than or equal to 12mm delta h2≤H2mm, obtaining a hot rolling with a thickness of 20-80 mmA plate;
calculate H2The formula is as follows:
H2＝0.07×Th－1500×b－25 (3)；
in the formula (3), ThThe initial rolling temperature of each pass is unit ℃; b is the mass content of boron element in the boron-containing stainless steel casting blank, unit percent;
(6) cutting off the end part of plain carbon steel formed by welding plain carbon steel plates at the front end and the rear end of the hot rolled plate, then carrying out solution treatment at the temperature of 950-1100 ℃ for 60-150 min, and then air-cooling to room temperature to prepare the boron-containing stainless steel thick plate with excellent plasticity and toughness.
In the step (2), the compression ratio of rough rolling is more than or equal to 2; the compression ratio is calculated by the formula Hp/HbIn which H ispThickness of boron-containing stainless steel ingot, HbIs the thickness of the rough rolled blank.
In the step (3), milling is carried out until the surface roughness Ra is less than or equal to 0.8 mu m.
In the step (3), the depth of the V-shaped groove is 3-5 mm, and the angle is 30-45 degrees.
In the step (3), the width-thickness ratio of the composite blank is more than or equal to 1.2.
In the step (4), the length of the common carbon steel plate is 3-5 times of the thickness of the common carbon steel plate.
In the step (4), the plain carbon steel with the mass percent of C less than 0.25% is selected as the plain carbon steel.
In the step (5), the cumulative compression ratio is more than or equal to 6+200 xb; the cumulative compression ratio is calculated by the formula Hp×n/HfIn which H isbThe thickness of the boron-containing stainless steel casting blank, n is the number of layers of the composite blank (namely the number of used composite blank monomers is 2-3), and HfIs the thickness of the hot-rolled plate; and b is the mass content of boron element in the boron-containing stainless steel casting blank, unit percent.
The principle of the invention is as follows: in order to avoid forming carborundum with a complex structure in a casting blank, ultralow carbon control is carried out on the boron-containing stainless steel; in order to eliminate the casting stress of the casting blank, reduce segregation and ensure smooth rough rolling, the casting blank needs to be rolled for a long time before rough rolling; in addition, as the solidus temperature of the stainless steel is mainly related to the boron content, different boron-containing stainless steel casting blanks are subjected to heat preservation at different temperatures in order to prevent overburning; in order to ensure that the rolled blank does not have edge crack, the reduction of each pass meets a specific formula, and the final rolling temperature is controlled; vacuum welding is carried out under the condition that the vacuum degree is less than or equal to 2.0Pa to form an uninterrupted welding seam, so that the oxidation of a composite blank monomer combination interface in the welding, heating and rolling processes can be prevented; plain carbon steel is welded at two ends, so that the composite blank is prevented from being layered due to uneven deformation in the thickness direction in the rolling process; in order to ensure that the composite blank can be effectively combined and edge cracking cannot occur, each pass of hot rolling is controlled; the solution treatment can eliminate the residual stress of the composite hot rolled plate and ensure that the room temperature structure is more uniform and stable.
In addition, the rough rolling reduction ratio is controlled to further homogenize and refine boride in the casting blank; performing surface finish machining on the boron-containing stainless steel composite blank until the surface roughness Ra is less than or equal to 0.8 mu m, cleaning and deoiling the finish-machined surface, and ensuring the flatness and cleanliness of a contact surface so that the boron-containing stainless steel composite blank can be effectively combined in the subsequent hot rolling process; in order to ensure the welding strength, the size of a processed V-shaped groove is selected; the welded plain carbon steel is too short, the blank is easy to fall off when being rolled and bitten, the limiting effect is lost, and the raw material is wasted if the blank is too long, so the length-thickness ratio of the plain carbon steel needs to be controlled; in order to ensure that boride in the composite blank is fully refined and uniformly distributed, the accumulated compression ratio of hot rolling is controlled.
The boron-containing stainless steel thick plate provided by the invention not only realizes effective combination of materials of each layer: in the deformation processes of three-point bending, stretching, impacting and the like, the conditions of layering, cracking and the like do not occur on the combined interface; but also realizes the control of uniform distribution and size dispersion of boride. The uniform and fine boride not only improves the uniform deformation capability of the finished plate, but also fully plays the dispersion strengthening role of the second phase particles, and the finally prepared boron-containing stainless steel thick plate has excellent plasticity and toughness.
Compared with the prior art, the process realizes the homogenization and fine control of boride in the finished product plate by improving the accumulated compression ratio of the boron-containing stainless steel thick plate, and effectively improves the performance of the boron-containing stainless steel thick plate; by effectively controlling the technological parameters of the processes of finish machining, vacuum welding, rough rolling, composite rolling and the like of the combined interface, the boron-containing stainless steel plates of all layers can be effectively combined, the plate shape and edge crack degree of the boron-containing stainless steel thick plate are improved, and the yield of the boron-containing stainless steel thick plate is effectively improved; in addition, the process has compact production flow, is convenient to realize mechanization and automation, and can obviously reduce the production energy consumption and cost.
Drawings
FIG. 1 is a partial flow chart of steps (3) to (5) in example 1 of the method for producing a boron-containing stainless steel slab excellent in ductility and toughness according to the present invention; in the figure, 1, rough rolling blank, 2, groove, 3, welding seam, 4, common carbon steel plate, 5 and hot rolling mill roller;
FIG. 2 is a photograph of the appearance of a boron-containing stainless steel slab with excellent ductility and toughness after failure in a three-point bending test according to example 1 of the present invention; in the figure, 1, crack, 2, bonding interface region;
FIG. 3 is a photograph of the appearance of a boron-containing stainless steel slab with excellent ductility and toughness after failure in a three-point bending test according to example 2 of the present invention; in the figure, 1, crack, 2, bonding interface region;
FIG. 4 is a photograph showing the appearance of a boron-containing stainless steel hot rolled ingot according to comparative example 2 of the present invention.
Detailed Description
The rough rolling blank prepared by the invention is a crack-free rough rolling blank.
The hot rolled plate prepared by the invention is a crack-free hot rolled plate.
The front and rear ends of the hot-rolled sheet of the present invention mean both ends in the length direction of the hot-rolled sheet.
The boron-containing stainless steel thick plate with excellent plasticity and toughness provided by the embodiment of the invention has the tensile strength of 565-690 MPa, the room-temperature elongation of 19-42%, and the room-temperature impact toughness of 220-530 KJ/m2。
In the boron-containing stainless steel thick plate with excellent plasticity and toughness, boride with the particle size of less than or equal to 3.0 mu m accounts for 22-31% of the total mass of all boride, and boride with the particle size of more than or equal to 15.0 mu m accounts for 2.9-4.2% of the total mass of all boride.
The equipment adopted for observing the microscopic structure in the embodiment of the invention is an Olympus BX53M type metallographic microscope and a JEOL JXA-8530F type electronic probe;
the dimensions of room temperature tensile specimens and their properties were determined in accordance with GB/T228-2002 using an Instron4206-006 tensile tester.
The dimension and the performance measurement method of the room-temperature Charpy-V port impact test sample in the embodiment of the invention are based on GB-T229-2007, and the adopted equipment is a ZBC2452-B pendulum impact tester.
The method for measuring the size and the performance of the room-temperature three-point bending test sample in the embodiment of the invention is based on GB T232-.
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The plain carbon steel with the mass percent of C being less than 0.25% is selected in the embodiment of the invention.
Example 1
Smelting molten steel, and then preparing the molten steel into a boron-containing stainless steel casting blank through die casting or continuous casting; the thickness of the boron-containing stainless steel casting blank is 160mm, and the boron-containing stainless steel casting blank comprises 18.5% of Cr, 14.6% of Ni, 0.7% of Mn, 1.25% of B, 0.31% of Si, 0.011% of C and the balance of Fe and inevitable impurity elements in percentage by mass;
heating the boron-containing stainless steel cast blank in a heating furnace to a soaking temperature T along with the furnace, preserving the heat for 120min, and then carrying out multi-pass rough rolling, wherein the final rolling temperature of the rough rolling is 940 ℃, and the reduction delta h of each pass1The delta h less than or equal to 10mm is satisfied1≤H1mm, obtaining a rough rolling blank with the thickness of 65 mm;
T＝(1155－1450×1.25％)＝1137℃；
h in the first rough rolling pass1＝0.065×1137－1500×1.25％－20＝74-39＝35mm；
The reduction ratio 160/65 of rough rolling is 2.46;
milling the rough rolling blank until the surface roughness Ra is less than or equal to 0.8 mu m, forming a V-shaped groove for welding on the outer edge of the top surface and/or the bottom surface, and then performing oil removal and drying treatment to prepare a composite blank monomer; stacking and aligning 2 composite blank monomers with the same size up and down, enabling V-shaped grooves formed in two adjacent composite blank monomers to be opposite, and then welding the two adjacent composite blank monomers at the V-shaped grooves under the vacuum condition that the vacuum degree is less than or equal to 2.0Pa to prepare a composite blank; wherein the depth of the V-shaped groove is 4mm, and the angle is 45 degrees; the width of the composite blank is 175mm, the thickness is 130mm, and the width-thickness ratio is 1.35;
welding and fixing end faces of front and rear ends of the composite blank with the end face of a common carbon steel plate respectively, wherein the width of the common carbon steel plate is the same as that of the composite blank, and the thickness of the common carbon steel plate is the same as that of the composite blank to prepare a combined blank; the length of the ordinary carbon steel plate is 450mm, which is 3.46 times of the thickness;
heating the combined blank to 1140 ℃, preserving heat for 120min, and then carrying out multi-pass hot rolling, wherein the final rolling temperature is 930 ℃, and the reduction delta h of each pass2Satisfies the requirement of less than or equal to 12mm delta h2≤H2mm, obtaining a hot rolled plate with the thickness of 30 mm;
h in the first hot rolling pass2＝0.07×1140－1500×1.25％－25＝79.8－18.8－25＝36mm；
The cumulative compression ratio 160 × 2/36 is more than or equal to 10.67 and more than or equal to 6+200 × 1.25% and more than or equal to 8.5;
the flow of the above partial steps is shown in FIG. 1;
cutting off the end part of plain carbon steel formed by welding the plain carbon steel plates at the front end and the rear end of the hot rolled plate, then carrying out solution treatment at the temperature of 1100 ℃ for 90min, and then air-cooling to room temperature to prepare the boron-containing stainless steel thick plate with excellent ductility and toughness, the thickness of 30mm, the tensile strength of 610MPa, the room-temperature elongation of 24 percent and the room-temperature impact toughness of 290KJ/m2；
In the boron-containing stainless steel thick plate with excellent plasticity and toughness, the boride with the grain diameter of less than or equal to 3.0 mu m accounts for 24 percent of the total mass of all the borides, and the boride with the grain diameter of more than or equal to 15.0 mu m accounts for 3.8 percent of the total mass of all the borides;
taking a three-point bending sample with the thickness of 5.0mm in a bonding interface area for detection, wherein the appearance of the sample after failure is shown in FIG. 2; in the deformation processes of stretching, impact and the like, the conditions of delamination, cracking and the like do not occur in the bonding interface area 2; the bonding interface can be effectively bonded, and the bonding strength is higher
Example 2
The method is the same as example 1, except that:
(1) the thickness of the boron-containing stainless steel casting blank is 220mm, and the components comprise 18.2% of Cr, 13.4% of Ni, 1.15% of Mn, 0.65% of B, 0.23% of Si and 0.013% of C in percentage by mass;
(2) heating the boron-containing stainless steel cast blank in a heating furnace along with the furnace to a soaking temperature T, preserving heat for 120min, and then carrying out multi-pass rough rolling at a final rolling temperature of 925 ℃ to obtain a rough rolling blank with the thickness of 60 mm;
T＝(1155－1450×0.65％)＝1146℃；
first pass rough rolling H1＝0.065×1146－1500×0.65％－20＝74.5－9.8-20＝44.7mm；
The rough rolling reduction ratio is 3.67;
(3) stacking the 3 composite blank monomers and performing vacuum welding to prepare a composite blank; the depth of the V-shaped groove is 4mm, and the angle is 40 degrees; the width of the composite blank is 360mm, the thickness is 180mm, and the width-thickness ratio is 2;
(4) the length of the common carbon steel plate is 550mm, which is 3.1 times of the thickness;
(5) heating the combined blank to 1150 ℃, preserving heat for 120min, and then carrying out multi-pass hot rolling at the final rolling temperature of 955 ℃ to obtain a hot rolled plate with the thickness of 75 mm;
h in the first hot rolling pass2＝0.07×Th－1500×b－25；
The cumulative compression ratio is 220 × 3/75 ≧ 8.8 ≥ 6+200 × 0.65 ≥ 7.4;
(6) the solution treatment temperature is 1000 ℃, and the time is 120 min; the boron-containing stainless steel thick plate with excellent plasticity and toughness has the thickness of 75mm, the tensile strength of 565MPa, the room-temperature elongation of 42 percent and the room-temperature impact toughness of 530KJ/m2The boride with the grain diameter not more than 3.0 mu m accounts for 31 percent of the total mass of all the borides, and the boride with the grain diameter not less than 15.0 mu m accounts for 2.9 percent of the total mass of all the borides;
a three-point bending sample with the thickness of 5.0mm is taken in a bonding interface area for detection, the appearance of the sample after failure is shown in figure 3, and when the sample fails in bending, the bonding interface area 2 is not layered or cracked, which shows that the bonding interface can be effectively bonded after the boron-containing stainless steel plate is hot rolled, and the bonding strength is high.
Example 3
The method is the same as example 1, except that:
(1) the thickness of the boron-containing stainless steel casting blank is 110mm, and the components comprise, by mass, 19.4% of Cr, 14.76% of Ni, 0.61% of Mn, 1.47% of B, 0.19% of Si and 0.009% of C;
(2) heating the boron-containing stainless steel cast blank in a heating furnace to a soaking temperature T along with the furnace, preserving the heat for 95min, and then carrying out multi-pass rough rolling at a final rolling temperature of 935 ℃ to obtain a rough rolling blank with the thickness of 50 mm;
T＝(1155－1450×1.47％)＝1134℃；
first pass rough rolling H1＝0.065×1134－1500×1.47％－20＝73.7－22.1－20＝31.6mm；
The rough rolling compression ratio is 2.2;
(3) stacking 2 composite blank monomers and carrying out vacuum welding to prepare a composite blank; the depth of the V-shaped groove is 4.5mm, and the angle is 45 degrees; the width of the composite blank is 400mm, the thickness is 100mm, and the width-thickness ratio is 4;
(4) the length of the common carbon steel plate is 500mm, which is 5 times of the thickness;
(5) heating the combined blank to 1130 ℃, preserving heat for 100min, and then carrying out multi-pass hot rolling at the final rolling temperature of 920 ℃ to obtain a hot rolled plate with the thickness of 20 mm;
h in the first hot rolling pass2＝0.07×1130－1500×1.47％－25＝79.1－22.1－25＝32mm；
The cumulative compression ratio is 110 × 2/20 ≥ 11 ≥ 6+200 × 1.47 ≥ 8.9;
(6) the solution treatment temperature is 950 ℃, and the time is 90 min; the boron-containing stainless steel thick plate with excellent plasticity and toughness has the thickness of 20mm, the tensile strength of 690MPa, the room-temperature elongation of 19 percent and the room-temperature impact toughness of 220KJ/m2Boride with the grain diameter not more than 3.0 mu m accounts for 22 percent of the total mass of all boride, and boride with the grain diameter not less than 15.0 mu m accounts for 4.2 percent of the total mass of all boride;
and (3) taking a three-point bending sample with the thickness of 5.0mm in the bonding interface area for detection, wherein when the sample fails in bending, the bonding interface area is not delaminated or cracked.
Comparative example 1
The method is the same as example 1, except that:
the rough rolling and final rolling temperature of the casting blank is 985 ℃, a rough rolling blank without edge crack of 90mm is obtained, and the rough rolling compression ratio is 1.78 (namely, the compression ratio is reduced);
heating the composite blank to 1140 ℃, preserving heat for 120min, and then carrying out hot rolling, wherein the final rolling temperature is 910 ℃, and the reduction delta h of each pass2In the same manner as in example 1, a 60mm thick hot-rolled sheet free from edge cracking was obtained, and the cumulative compression ratio was 5.33 (cumulative compression ratio decreased);
a three-point bending sample with the thickness of 5.0mm is taken in a bonding interface area for detection, and because the rough rolling compression is small, the size of boride in a rough rolling blank is still large and uneven in distribution, so that the bonding effect of the composite blank is influenced; therefore, after the three-point bending test sample fails, the bonding interface part area is layered; in the deformation processes of stretching, impact and the like, the conditions of delamination, cracking and the like also occur in the partial area of the combined interface; because the cumulative compression ratio is lower, the proportion of boride with the grain diameter smaller than 3.0 mu m in the finished plate is only 17.5 percent, and the proportion of boride with the grain diameter larger than 15.0 mu m is 7.8 percent; the finally prepared boron-containing stainless steel thick plate has the tensile strength of 640MPa, the room-temperature elongation of 16.7 percent and the room-temperature impact toughness of 165KJ/m2。
Comparative example 2
The method is the same as example 1, except that:
welding and assembling under the vacuum condition that the vacuum degree is less than 2.0Pa to obtain a double-layer composite blank with the width of 175 mm; plain carbon steel is not welded at the two ends of the composite blank respectively;
after the composite blank is heated and insulated, the second pass is bitten into the composite blank and falls off in the hot rolling deformation process, the appearance of the boron-containing stainless steel hot rolling blank is shown in figure 4, layering occurs, and effective combination and continuous rolling cannot be realized.
Comparative example 3
The method is the same as the embodiment 3, and is different from the following steps:
the boron-containing stainless steel casting blank comprises the following components in percentage by mass: 19.1% of Cr, 13.5% of Ni, 1.78% of Mn, 1.61% of B, 0.13% of Si and 0.015% of C; the balance of Fe and inevitable impurity elements (namely, the content of boron in the stainless steel is increased);
the rough rolling final temperature of the casting blank is 945 ℃, and the reduction delta h of each pass1The thickness is 20mm, and because the boron content B% is too high and the reduction per pass is too large, the obtained 50mm rough rolling billet has obvious edge crack; heating, insulating, hot rolling and deforming the composite blank to obtain a composite hot rolled plate with the thickness of 20mm and the accumulated compression ratio of 11, wherein the edge of the composite hot rolled plate is slightly cracked;
after the solution treatment at 950 ℃ for 90min, obtaining a boron-containing stainless steel thick plate; because the boron content B% is too high, the boride in the casting blank is large in quantity and large in size; the boride with large size after rough rolling deformation is still high in proportion, and the combination effect of the composite blank is influenced, so that the combination interface part area is layered after the three-point bending sample fails; in the deformation processes of stretching, impact and the like, the conditions of delamination, cracking and the like also occur in the partial area of the combined interface; the proportion of boride with the grain diameter of less than 3.0 mu m in the finished plate is 14.5 percent, and the proportion of boride with the grain diameter of more than 15.0 mu m is 6.5 percent; the finally prepared boron-containing stainless steel thick plate has the tensile strength of 715MPa, the room-temperature elongation of 13.3 percent and the room-temperature impact toughness of 153KJ/m2。

Claims (6)

1. The preparation method of the boron-containing stainless steel thick plate with excellent plasticity and toughness is characterized by comprising the following steps of:
(1) smelting molten steel, and then preparing the molten steel into a boron-containing stainless steel casting blank through die casting or continuous casting; the thickness of the boron-containing stainless steel casting blank is 100-250 mm, and the boron-containing stainless steel casting blank comprises 18.0-20.0% of Cr, 12.0-15.0% of Ni, 0.2-2.0% of Mn, 0.5-1.5% of B, less than or equal to 0.5% of Si, less than or equal to 0.02% of C, and the balance of Fe and inevitable impurity elements by mass percent;
(2) putting the boron-containing stainless steel casting blank into a heating furnace, heating the boron-containing stainless steel casting blank along with the furnace to a soaking temperatureTKeeping the temperature for 90-150 min, and then carrying out multi-pass rough rolling and rough rolling finishingThe rolling temperature is 900-1000 ℃, and the reduction per pass is△h 1 Meet the requirement of less than or equal to 10mm△h 1 ≤H 1 mm, obtaining a rough rolling blank with the thickness of 30-80 mm;
calculating soaking temperatureTThe formula is as follows:
T=（1155－1450×b）℃ （1）；
computingH 1 The formula is as follows:
H 1 =0.065×T h －1500×b－20 （2）；
in the formulas (1) and (2),T h the initial rolling temperature of each pass is unit ℃;bthe percentage by mass of boron element in the boron-containing stainless steel casting blank is unit percent;
(3) milling the rough rolling blank, forming a V-shaped groove for welding on the outer edge of the top surface and/or the bottom surface, and performing oil removal and drying treatment to prepare a composite blank monomer; stacking and aligning 2-3 composite blank monomers with the same size up and down, enabling V-shaped grooves formed in two adjacent composite blank monomers to be opposite, and then welding the two adjacent composite blank monomers at the V-shaped grooves under the vacuum condition that the vacuum degree is less than or equal to 2.0Pa to prepare a composite blank;
(4) welding and fixing end faces of front and rear ends of the composite blank with the end face of a common carbon steel plate respectively, wherein the width of the common carbon steel plate is the same as that of the composite blank, and the thickness of the common carbon steel plate is the same as that of the composite blank to prepare a combined blank;
(5) heating the combined blank to 1100-1150 ℃, preserving heat for 60-150 min, and then carrying out multi-pass hot rolling at the final rolling temperature of 900-1000 ℃ with the reduction of each pass△h 2 Meet the requirement that the thickness is less than or equal to 12mm△h 2 ≤H 2 mm, obtaining a hot rolled plate with the thickness of 20-80 mm;
computingH 2 The formula is as follows:
H 2 =0.07×T h －1500×b－25 （3）；
in the formula (3), the first and second groups,T h the initial rolling temperature of each pass is unit ℃;bthe mass content of boron element in the boron-containing stainless steel casting blank is unit percent; the accumulated compression ratio after hot rolling is more than or equal to 6+200b；
(6) Cutting off the end part of plain carbon steel formed by welding plain carbon steel plates at the front end and the rear end of the hot rolled plate, then carrying out solution treatment at the temperature of 950-1100 ℃ for 60-150 min, and then air-cooling to room temperature to prepare the boron-containing stainless steel thick plate with excellent plasticity and toughness.
2. The method for preparing the boron-containing stainless steel thick plate with excellent plasticity and toughness as claimed in claim 1, wherein in the step (2), the reduction ratio of rough rolling is not less than 2.
3. The method according to claim 1, wherein in step (3), the surface roughness Ra of the slab is milled to 0.8 μm or less.
4. The method according to claim 1, wherein in the step (3), the depth of the V-shaped groove is 3-5 mm, and the angle is 30-45 °.
5. The method for preparing the boron-containing stainless steel thick plate with excellent ductility and toughness as claimed in claim 1, wherein in the step (3), the width-to-thickness ratio of the composite billet is not less than 1.2。
6. The method for preparing the boron-containing stainless steel thick plate with excellent ductility and toughness as claimed in claim 1, wherein in the step (4), the length of the ordinary carbon steel plate is 3-5 times of the thickness.
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