CN112593153A - High-temperature-oxidation-resistant high-toughness laser tailor-welded blank and hot stamping process thereof - Google Patents
High-temperature-oxidation-resistant high-toughness laser tailor-welded blank and hot stamping process thereof Download PDFInfo
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- 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
- B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/673—Quenching devices for die quenching
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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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- 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
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- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- 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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- 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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- 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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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- 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
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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- 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
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Abstract
The invention provides a high-temperature oxidation resistant and high-strength and high-toughness laser tailor-welded blank and a hot stamping process thereof, wherein the laser tailor-welded blank is formed by butt joint of two or more welding parent metals, at least one of the welding parent metals can be subjected to hot press hardening, and the welding parent metals are provided with coatings of aluminum and compounds thereof, zinc and compounds thereof; the tailor-welded zone comprises the following components in percentage by weight: 0.20-0.40% of C, 0.5-1.5% of Cr, 1.5-4.5% of Mn + Ni, and 0-1.5% of Al which is introduced into a tailor-welded area from a base material coating in a tailor-welding process. According to the invention, the welding wires are filled, so that the Ni content in the tailor-welded zone reaches 1.5-4.0%, and the Cr content reaches 0.5-1.5%, and the laser tailor-welded blank with excellent high-temperature oxidation resistance, corrosion resistance and mechanical properties in the tailor-welded zone is obtained. In the hot stamping process, the laser tailor-welded blank is subjected to austenitizing annealing without atmosphere protection, a tailor-welded weld joint is corrosion-resistant without protective oil coating, and the hydrogen embrittlement resistance of a tailor-welded area is improved by over 30 percent.
Description
Technical Field
The invention mainly relates to the technical field of laser tailor-welding and hot stamping, in particular to a high-temperature oxidation resistant and high-toughness laser tailor-welded blank and a hot stamping process thereof, which are suitable for designing and manufacturing the laser tailor-welded blank and hot stamping parts thereof.
Background
In recent years, the lightweight technology of automobiles represented by high-strength steel hot stamping is developed vigorously, and the lightweight technology is widely applied to automobile body safety structural members such as automobile A columns, B columns and central channel plates, and the market scale reaches the billion level. The hot stamping technology is that boron steel is heated in an austenite phase region, transferred to a hot stamping die within 7-15s, and subjected to stamping plastic forming at the temperature of 700-850 ℃, and finally subjected to quenching, pressure maintaining and cooling in the die. Taking 22MnB5 hot stamping parts as an example, the yield strength reaches 950 + 1150MPa, the fracture strength reaches 1350 + 1500MPa, but the elongation is only 5-7%, and the strength-elongation and collision energy absorption effects of the hot stamping component are poor. Based on the service working condition of the parts, sectional strengthening technologies such as soft zone dies, differential thick plates and the like are provided so as to realize the unification of the integral rigidity and the collision energy absorption of the hot stamping parts.
The laser tailor welding technique is to use laser as a heat source to butt-weld metals of different materials, different thicknesses or different coatings to manufacture an integrated plate or coil. The laser tailor-welding method has the advantages of high material utilization rate, convenience for performance customization and structural topological design. With the development of light weight of automobiles, people apply laser tailor-welding to the technical field of hot stamping, and develop automobile body safety structural members such as A columns, B columns, door rings and the like. However, when the joined plating plates are subjected to laser tailor welding, Al in the joined base metal plating layer enters into the tailor welding area, which causes the austenite phase area in the tailor welding area to be closed and high-temperature ferrite to remain, and finally causes deterioration of the weld strength and toughness of the hot-stamped parts.
In order to solve the problems, anserol provides a tailor-welding process for partially removing a coating, so that the weld performance deterioration caused by excessive Al entering a tailor-welding area is avoided, and the tailor-welding area has certain corrosion resistance, and the invention is disclosed in the published patent of hot-forming pre-welded steel part with very high mechanical resistance and a production method thereof, and is disclosed in the patent No. CN 103917329B. However, the plating layer is partially removed, the requirements on the flatness of the butt-jointed base metal, the contour degree of the splicing surface of the butt-jointed base metal and the tailor-welded gap are extremely high, the process control is complex, the product rejection rate is high, and the problem of oxidation of the tailor-welded area in the austenitizing process is solved. In order to solve the above problems, the modern iron-making method proposes to regulate the composition of the tailor-welded zone by filler wire welding without removing the plating layer of the butt-jointed base metal, and the invention is disclosed in the patent publication "tailor-welded blank and manufacturing method thereof, and hot-stamped part using the tailor-welded blank", and is disclosed in patent No. CN 104023899B. Although the scheme reduces the requirements of the flatness and the butt joint clearance of the plate materials in the butt welding link, the problem of oxidation of the butt welding area in the hot stamping process is also not solved, and the problem that the plate materials are easy to corrode when being placed is solved.
Patent No. CN103614640B discloses a high-temperature oxidation resistant steel for hot stamping forming of non-coating, which provides a high-temperature oxidation resistant hot stamping high-strength steel component, and the Cr content is increased to 0.5-1.5%, so that the steel plate obtains a compact oxidation film when the austenite is heated, and further oxidation is prevented. On the basis of the technology, researchers optimally design and regulate the components of the tailor-welded area of the laser tailor-welded blank so as to improve the high-temperature oxidation resistance and the toughness of the laser tailor-welded blank.
In conclusion, the laser tailor-welded clad plate with excellent high-temperature oxidation resistance, corrosion resistance and hydrogen embrittlement resistance in the tailor-welded area is developed, and the process window of hot stamping of the laser tailor-welded clad plate is established, so that the difficult problem in the field is solved.
Disclosure of Invention
Aiming at the problems that the tailor-welded area of the laser tailor-welded blank is oxidized in the hot forming process and the tailor-welded area of the laser tailor-welded blank and parts thereof are easy to corrode after being placed for a long time in the prior art. According to the invention, the Mn + Ni content and the Cr content of the tailor-welded blank of the laser tailor-welded blank reach 1.5-4.5% and 0.5-1.5% through welding by the filler wire, so that the laser tailor-welded blank with excellent high-temperature oxidation resistance, corrosion resistance and mechanical property is obtained. The laser tailor-welded blank does not need atmosphere protection during austenitizing annealing, and the corrosion resistance and hydrogen embrittlement resistance of a tailor-welded area are improved by more than 30% compared with those of a base material.
The invention provides a high-temperature oxidation resistant and high-strength and high-toughness laser tailor-welded blank, which is formed by butt joint of two or more welding base metals, wherein the welding base metals are plates or coils, at least one welding base metal can be subjected to hot press hardening, and the welding base metals are provided with coatings of aluminum and compounds thereof, zinc and compounds thereof;
the welding method is characterized in that the tailor-welded area comprises the following components in percentage by weight: 0.20-0.40% of C, 0.5-1.5% of Cr, 1.5-4.5% of Mn + Ni, and 0-1.5% of Al which is introduced into a tailor-welded area from a base material coating in a tailor-welding process.
Preferably, the thickness of the welding parent metal for butt joint is 0.8-2.5mm, and the difference in the thickness of the welding parent metal is <1.5 mm.
Preferably, at least one plate material or coil material in the welding parent metal comprises the following components in percentage by weight: 0.10 to 0.40 percent of C, 0.5 to 2.5 percent of Mn, 0.5 to 2.5 percent of Si, less than 0.5 percent of Cr, less than 0.5 percent of Mo, Ti, Nb and V, less than 0.008 percent of B, and the balance of Fe and impurities.
In the field of automobile body structure parts, the base material used by the laser tailor-welded blank can be any one or a combination of multiple of PHS steel and DP steel, QP steel, TRIP steel and low-density steel.
Preferably, the width of the tailor-welded zone of the tailor-welded blank is 0.5-4mm, and the tailor-welded blank comprises the following components in percentage by weight: 0.25 to 0.35 percent of C, 0.5 to 2.0 percent of Mn, 1.5 to 4.0 percent of Ni, 1.0 to 1.5 percent of Cr, less than 0.5 percent of Mo, less than 0.008 percent of B, less than 0.3 percent of Nb, V and Ti, and the balance of Fe and impurities.
The reason for the composition of the tailor welded zone is as follows:
0.25-0.35% of carbon C. The most basic strengthening element improves the strength of steel by martensitic strengthening. However, after the C content is excessively high, a large amount of twin crystal martensite appears after the hot stamping, so that the plasticity and toughness of the material are reduced. In order to ensure that the strength of the tailor-welded zone is not lower than that of the parent metal and no twin martensite is formed, the carbon content is required to be 0.05-0.1% higher than that of the parent metal but not more than 0.35%.
0.5 to 2.0 percent of manganese Mn. The austenite phase region is enlarged, and the solid solution strengthening effect is achieved. Meanwhile, Mn is a good deoxidizer and desulfurizer, can effectively reduce the brittle transition temperature and hot brittleness of steel, and improve the hot workability of the steel. However, Mn is an easily oxidizable element, and too high a content thereof lowers the oxidation resistance of the steel and is disadvantageous in welding performance, and therefore, it is controlled to 0.5 to 2.5%.
1.5 to 4.0 percent of nickel Ni. The austenite phase region is enlarged and the solid solution strengthening effect is achieved. Researches show that Al in a coating enters a tailor-welded area in the tailor-welded process, an austenite phase area of the tailor-welded area is closed, and a large amount of high-temperature ferrite residues are caused to deteriorate hot-stamped parts. By adding a certain amount of Ni, the influence of Al on the structure and the performance of the splicing welding area can be eliminated. In addition, the partial replacement of Mn by Ni can enlarge the austenitizing phase region and further improve the oxidation resistance of the tailor-welded zone.
1.0 to 1.5 percent of chromium Cr. The hardenability of the steel is improved. In the invention, the austenite exists mainly in a solid solution form, so that the stability of austenite can be improved, and the hardenability of a tailor-welded zone is further improved. More importantly, when the Cr content exceeds 0.8%, a compact Cr2O3 oxide film can be formed on the surface layer of the tailor-welded area, so that the further oxidation of the material is prevented, and the oxidation degree of the tailor-welded area heated in the air is ensured to be close to that of the base metal of the plating plate. In addition, Cr has higher chemical potential and material passivation performance, and can reduce the corrosion rate of a splicing welding area, so that the material has the corrosion resistance which is comparable to that of a plating plate. However, Cr reduces the austenite phase region, and after the content exceeds 1.5%, the improvement effect on the oxidation resistance of the tailor-welded zone is redundant, so the Cr content is controlled to be 0.8-1.5% by the invention.
0 to 0.5 percent of molybdenum Mo. The room temperature strength and the heat strength of the tailor-welded zone are improved, and the high-temperature forming performance of the tailor-welded zone is improved. The solid solution exists in austenite, so that the stability and hardenability of the austenite are improved, and the full martensite structure is favorably obtained. However, since the strengthening effect is more than 0.5% by Mo, the Mo content is controlled to 0 to 0.5% by the present invention.
0 to 0.008 percent of boron B. The key element for improving the hardenability of the steel can obviously influence the hardenability of the steel by adding trace elements. However, when the content exceeds 0.005%, the influence on the hardenability of the steel is not so large, so that the Mo content is controlled to 0 to 0.008% in the present invention.
Niobium + vanadium + titanium Nb + V + Ti: 0 to 0.30 percent. As a strong carbide former, they are present in steel predominantly in dispersion-strengthened form. By adding a small amount of Ti, Nb and V, the structure of a splicing welding area can be refined, coarsening of matrix grains in the austenitizing process can be prevented, and the toughness of the material is improved. More importantly, carbides such as NbC, VC and the like can form a hydrogen trap, and the hydrogen embrittlement resistance of the tailor-welded area is greatly improved. In addition, Ti and N, O have strong binding force, and can play a role in deoxidation and N fixation, so that B is prevented from being combined with N to form BN.
The invention also provides a high-temperature oxidation resistant and high-toughness hot stamping process for the laser tailor-welded blank, which uses the laser tailor-welded blank of claim 1, and is characterized by comprising the following steps:
s1, austenitizing and heating: heating the laser tailor-welded blank in the air to 800-950 ℃, and keeping the temperature for 3-15min to ensure that the tailor-welded area and the non-tailor-welded area are completely austenitized;
because the tailor-welded zone has higher oxidation resistance, the laser tailor-welded blank can avoid oxidation and decarburization of the tailor-welded zone without inert gas or reducing atmosphere protection, and the hot stamping manufacturing cost of parts of the laser tailor-welded blank is greatly reduced.
S2, transferring the plate: transferring the laser tailor-welded blank completely austenitized within 5s-15s into a hot stamping die provided with a cooling system;
s3, press forming: and (3) closing the die, completing the stamping and forming of the laser tailor-welded blank at the temperature of 650 plus 850 ℃, and performing pressure maintaining and quenching on the laser tailor-welded blank in the die for 5-15s until the laser tailor-welded blank is cooled to 50-250 ℃, and then taking out the parts.
Preferably, in the step S3, in the pressure maintaining and quenching process of the mold, the cooling rate of the tailor welded blank region to obtain the full martensite structure is greater than 15 ℃/S.
This is because the tailor welded zone has a larger amount of austenitizing stabilizing elements and a higher quenching sensitivity than the base material. Therefore, the hot stamping die can be designed to avoid the splicing welding area, so that the splicing welding area can obtain full martensite at a lower cooling rate, and the manufacturing and debugging difficulty and cost of the corresponding die are reduced.
The invention has the beneficial effects that:
1. the tailor-welded blank is in the austenitizing heating stage, and does not need to be protected by atmosphere: the laser tailor-welded blank has 0.5-1.5% of Cr, and forms compact Cr2O3 in the austenitizing and heating stage without additionally introducing inert or reducing atmosphere, so that the manufacturing cost and the equipment complexity in the hot stamping stage are reduced;
2. the tailor-welded blank has good corrosion performance, and does not need to be coated with protective oil for protection: according to the laser tailor-welded blank, the tailor-welded area has high Ni and Cr elements and Al introduced in the tailor-welded blank manufacturing process, the tailor-welded area has high corrosion resistance, and rust-proof oil does not need to be additionally coated, so that the protection difficulty of the laser tailor-welded blank and parts thereof is simplified;
3. the tailor-welded blank has good high-temperature formability, and the tailor-welded area is not easy to crack and wrinkle: the laser tailor-welded blank has C, Mo and Cr elements higher than those of the base material in the tailor-welded area, has higher heat strength and work hardening rate, and can effectively avoid tearing and wrinkling in the tailor-welded area. In addition, the tailor-welded area has higher hardenability than the base material, the die can carry out avoidance design of less than 20mm near the tailor-welded area of the laser tailor-welded blank without influencing the strength of the tailor-welded area, and the difficulty of die design and debugging is reduced;
4. the tailor-welded blank has strong hydrogen embrittlement resistance, and the room temperature strength is higher than that of the base metal: according to the laser tailor-welded blank, the tailor-welded area has elements such as C, Ni, Mo, Nb + Ti + V and the like higher than that of the base material, and the strength of the tailor-welded area reaches 100-150% of that of the base material. Meanwhile, Nb, Ti and V dispersion carbides are separated out during austenitizing heating, austenite grains are refined, a hydrogen trap is formed, and hydrogen brittleness sensitivity of a tailor-welded zone is reduced.
Drawings
FIG. 1 is a schematic view of a laser tailor welded base material according to the present invention;
FIG. 2 is a schematic view of the present invention relating to a laser tailor welding process;
FIG. 3 is a schematic view of the present invention with respect to an integral door ring tailor welded blank;
FIG. 4 is an organization chart of a tailor welded blank according to the present invention;
FIG. 5 is a schematic view of the components of the present invention with respect to an integral door ring;
FIG. 6 is an organizational chart of the present invention relating to the area of the tailor welded integral door ring components;
in the figure, the position of the upper end of the main shaft,
1. a laser heat source; 2. filling welding wires; 3. butt-jointing a base material 1; 4. welding seams in a splicing mode; 5. butt-jointing the parent metal 2.
Detailed Description
In order to make the technical solutions of the present invention better understood and make the above features, objects, and advantages of the present invention more comprehensible, the present invention is further described with reference to the following examples. The examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.
The component design principle and the hot stamping process of the high-temperature oxidation resistant and high-strength and high-toughness laser tailor-welded blank are explained below by taking the integral door ring as an example. The laser tailor-welded blank is formed by tailor-welding a plurality of 22MnB5 plating plates with the thickness of 1.6mm and 2.0 mm. The main components of the tailor-welded zone are as follows: 0.25 to 0.32 percent of C, 0.8 to 1.2 percent of Cr, 3.0 to 4.0 percent of Mn + Ni and 0.1 to 0.3 percent of Mo.
Composition design of laser tailor-welded blank
The method takes a 22MnB5 aluminum-silicon plating layer plate with the plate thickness of 1.6mm and 2.0mm as a butt joint base metal, and regulates and controls the components of a splicing welding area through laser wire filling welding, so that the content of Cr in the splicing welding area reaches 0.8-1.2%, the content of Ni reaches 2.5-3.5%, and the content of other elements is higher than that of the base metal by 10-25%, which is shown in Table 1.
TABLE 1 chemical composition of laser tailor welded blanks
The design principle of the laser tailor-welded blank of the invention is as follows:
the carbon C improves the strength of the splicing welding area of the laser splicing welding plate through martensite strengthening, and in order to ensure that the strength of the splicing welding area is higher than that of a parent metal and twin martensite is not formed, the carbon content of the splicing welding area is 0.05-0.1% higher than that of the parent metal 22MnB 5. The Mn + Ni is used for expanding an austenite phase region of a tailor-welded zone and reducing the formation of high-temperature ferrite, and the deterioration of the toughness of the material caused by the fact that excessive Al in a plating plate enters the tailor-welded zone is eliminated; the invention uses Ni to replace Mn to improve the oxidation resistance of the tailor-welded zone.
The chromium Cr is used for improving the oxidation resistance and the corrosion resistance of the tailor-welded zone, a compact Cr2O3 oxidation film is formed in the tailor-welded zone at high temperature, further oxidation of steel is prevented, and the laser tailor-welded blank does not need N2 protection when being heated in an austenitizing mode; in addition, Cr has certain passivation property, can inhibit the corrosion of the tailor-welded area, and enables the tailor-welded area to obtain the corrosion resistance which is comparable to that of a plating plate. The molybdenum Mo is used for improving the heat strength of the splicing welding area and avoiding tearing and wrinkling of a welding line in the hot stamping process. Boron B is a key element for improving the hardenability, the hardenability of the steel can be obviously influenced by adding trace elements, the mold can be designed to avoid gaps near the tailor-welded area, and the full martensite structure can be obtained. V is used for refining austenitizing crystal grains and improving the hydrogen embrittlement resistance of the tailor-welded zone.
Second, preparation technology of laser tailor-welded blank
According to the relation among the base metal, the welding wire and the components of the welding area, the invention adopts filler wire welding to complete the connection of the butt-jointed base metal. The preparation process comprises the following steps:
s1, preparing a parent material. The welding parent metal is 22MnB5 with an aluminum-silicon plating plate, and the thickness of the plate is 1.6mm and 2.0 mm; before welding processing, determining whether to remove a coating from the butted base metal and determining the proportion of the removed coating according to the requirements of a welding process; butt-jointing the parent metal, wherein the butt-jointing gap is 0.1-0.5mm, and is shown in figure 1.
And S2, welding, namely welding the welding parent metal by using a laser heat source, wherein the melting ratio of the welding parent metal is controlled to be 25-75%. The tailor-welding process parameters are as follows: the laser power is 1.5-4.0KW, the spot diameter is 0.5-2mm, the scanning speed is 3-6m/min, the included angle between the welding wire and the heat source light beam is 45-55 degrees, as shown in figure 2.
The performance of the laser tailor-welded blank prepared by the invention is compared with that of the similar patent products, and the performance is shown in figures 3 and 4. As shown in Table 2, the material properties of the integral door ring and similar patent products, such as high temperature oxidation resistance, quenching sensitivity, salt spray test, hardness, strength and the like, are provided.
Table 2: the invention is compared with the performance of the similar patent products
Compared with an Ansilox patent product, the laser tailor-welded blank has excellent oxidation resistance, N2 does not need to be introduced for atmosphere protection in an austenitizing stage, the salt spray test performance is approximately equal to that of a 22MnB5 plating plate, and the process cost of a hot stamping link is reduced. Compared with the modern iron manufacturing patent product, the laser tailor-welded blank has higher corrosion resistance in the tailor-welded area, the salt spray test is approximately equal to that of a 22MnB5 coating plate, and the protection of protective oil coating is not needed.
In addition, the heat intensity of the splicing welding area of the laser splicing welding plate is 10-25% higher than that of the base metal, so that the cracking risk of the splicing welding seam in the hot stamping process is reduced; the tailor-welded area of the laser tailor-welded blank has higher quenching sensitivity, and the die is subjected to an avoidance design of less than 20mm near the tailor-welded area, so that the performance of the tailor-welded area is not influenced.
Hot stamping process for laser tailor-welded blank parts
The tailor-welded area of the laser tailor-welded blank has oxidation resistance, and inert or reducing atmosphere protection is not needed in the hot stamping process, so that the hot stamping process cost of the laser tailor-welded blank structural member is reduced. The hot stamping process of the laser tailor-welded blank of the invention comprises the following steps:
s1, austenitizing and heating. Heating the laser tailor-welded blank in the air to 850-950 ℃, keeping the temperature for 3-10min, and enabling the tailor-welded area and the non-tailor-welded area to be completely austenitized without atmosphere protection.
And S2, transferring the plates. And transferring the laser tailor-welded blank completely austenitized within 7-10s to a hot stamping die, wherein a water path cooling system is arranged inside the hot stamping die.
And S3, stamping and forming. And (3) closing the die, completing the stamping and forming of the laser tailor-welded blank at the temperature of 700 plus 850 ℃, performing pressure maintaining quenching for 5-15s in the die, and loading the pressure to 5-15MPa until the plate is cooled to 50-150 ℃, and then taking out the laser tailor-welded structural part, as shown in figure 5.
As shown in FIG. 6, the structure of the tailor-welded area after the laser tailor-welded integral door ring is hot stamped is shown, and the tailor-welded area is mainly martensitic. Furthermore, after 3 months of shelf life in air, the tailor welded area showed no significant corrosion. In the subsequent use process, the splicing welding area does not need to be protected by oiling, so that the subsequent maintenance cost of the product is reduced.
The above-described embodiments are merely illustrative of the principles and utilities of the present patent application and are not intended to limit the present patent application. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of this patent application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of this patent application.
Claims (6)
1. A high-temperature oxidation resistant and high-strength and high-toughness laser tailor-welded blank comprises two or more welding parent metals which are butted, wherein the welding parent metals are plates or coils, at least one of the welding parent metals can be subjected to hot press hardening, and the welding parent metals are provided with coatings of aluminum and compounds thereof, zinc and compounds thereof;
the welding method is characterized in that the tailor-welded area comprises the following components in percentage by weight: 0.20-0.40% of C, 0.5-1.5% of Cr, 1.5-4.5% of Mn + Ni, and 0-1.5% of Al which is introduced into a tailor-welded area from a base material coating in a tailor-welding process.
2. The high temperature oxidation resistant, high toughness laser tailor welded blank according to claim 1, wherein: the thickness of the welding parent metal for butt joint is 0.8mm-2.5mm, and the difference of the thicknesses of the welding parent metal is less than 1.5 mm.
3. The high temperature oxidation resistant, high toughness laser tailor welded blank according to claim 2, wherein: at least one plate material or coil material in the welding parent metal comprises the following components in percentage by weight: 0.10 to 0.40 percent of C, 0.5 to 2.5 percent of Mn, 0.5 to 2.5 percent of Si, less than 0.5 percent of Cr, less than 0.5 percent of Mo, Ti, Nb and V, less than 0.008 percent of B, and the balance of Fe and impurities.
4. The high temperature oxidation resistant, high toughness laser tailor welded blank according to claim 1, wherein: the width of a tailor-welded zone of the tailor-welded blank is 0.5-4mm, and the tailor-welded blank comprises the following components in percentage by weight: 0.25 to 0.35 percent of C, 0.5 to 2.0 percent of Mn, 1.5 to 4.0 percent of Ni, 1.0 to 1.5 percent of Cr, less than 0.5 percent of Mo, less than 0.008 percent of B, less than 0.3 percent of Nb, V and Ti, and the balance of Fe and impurities.
5. A high-temperature oxidation resistant and high-toughness laser tailor-welded blank hot stamping process, which uses the laser tailor-welded blank of claim 1, is characterized by comprising the following steps:
s1, austenitizing and heating: heating the laser tailor-welded blank in the air to 800-950 ℃, and keeping the temperature for 3-15min to ensure that the tailor-welded area and the non-tailor-welded area are completely austenitized;
s2, transferring the plate: transferring the laser tailor-welded blank completely austenitized within 5s-15s into a hot stamping die provided with a cooling system;
s3, press forming: and (3) closing the die, completing the stamping and forming of the laser tailor-welded blank at the temperature of 650 plus 850 ℃, and performing pressure maintaining and quenching on the laser tailor-welded blank in the die for 5-15s until the laser tailor-welded blank is cooled to 50-250 ℃, and then taking out the parts.
6. The high-temperature-oxidation-resistant high-toughness laser tailor-welded blank hot stamping process according to claim 5, characterized in that: in the S3, in the pressure maintaining and quenching process of the die, the cooling rate of the full martensite structure obtained in the tailor-welded zone of the laser tailor-welded blank is more than 15 ℃/S.
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