Patent Description:
In today's society, automobiles are more and more popularized. As the vehicle population rises steadily, there is growing concern about the conflict between vehicle exhaust emission and environmental protection. Reduction of vehicle weight may help reduce oil consumption and exhaust emission. Hence, high strength and thinning become a trend for development of automotive materials. Hot stamping is a conventional process for imparting high strength to parts and components by way of combining heat treatment and high-temperature forming to provide a product with high strength. Laser tailor-welded blank hot stamping can reduce the number of parts in a vehicle body and increase manufacture precision while reducing weight.

Common laser tailor-welded hot stamped products mainly include safety structural members such as A pillars, B pillars, center tunnels, etc. These hot stamped products are characterized by high strength, complex shape, good formability, high dimensional precision, small rebound resilience, differential strength, differential thickness, etc. A differential-strength tailor-welded member for a B pillar represents a trend for development of an automotive material, generally formed by tailor welding one steel plate having a tensile strength of <NUM> MPa - <NUM> MPa after hot stamping to another steel plate having a tensile strength of <NUM> MPa-<NUM> MPa after hot stamping. Steel plates for hot stamping include bare steel plates without clad layers and steel plates with clad layers when classified according to surface state. Because hot stamped steel plates with clad layers exhibit better resistance to corrosion and high-temperature oxidation than bare steel plates, and need no shot blasting or pickling after the hot stamping, they have attracted more and more attention. The thermally formed steel in the most common use is hot-stamped steel with an aluminum or aluminum alloy clad layer. However, in the process of welding this kind of material, the clad layer melts into a molten pool under the influence of welding heat, forming brittle and rigid intermetallic compounds with iron (FesAl, Fe<NUM>Al<NUM>, FeAl<NUM>). In post-welding heat treatment, these intermetallic compounds will further grow, resulting in notable decrease in the strength and ductility of the welded joint, such that the requirements for use in automobile plants cannot be satisfied.

Chinese Patent Publication <CIT> discloses a process for manufacturing a welding blank from a steel plate with an aluminum-silicon clad layer, wherein the welding blank only comprises a pre-coating of an intermetallic compound. In particular, the aluminum alloy layer in the clad layer is removed in order to avoid melting of excessive aluminum in a molten pool, while the intermetallic compound layer remains in the clad layer. Thereafter, the welding blank is subjected to welding and hot stamping. Despite the removal of the alloy layer from the clad layer in this patent application, the remaining intermetallic compound layer (having a thickness of <NUM>-<NUM>) still enables introduction of the elements in the clad layer into a welding line. If controlled improperly, the properties of the welding line will be degraded easily. In addition, the remaining of the several micrometers of clad layer renders steady operation very difficult, increasing risk in production.

Moreover, the published patent applications <CIT> and <CIT> disclose laser welding methods according to prior art.

The object of the present invention is to provide a method for manufacturing a differential-strength steel welded component with an aluminum or aluminum alloy clad layer, thereby solving a problem accompanying welding of a high-strength steel plate and a low-strength steel plate: the elements in the clad layer immigrate to a welding line, such that tensile strength of the welding line after hot stamping is less than the strength of the base material of the low-strength steel, and thus the welding line tends to fracture when the component is loaded. When the welded component obtained according to the present invention is used, its welding line has a tensile strength that is higher than the tensile strength of the base material of the low-strength steel, and an elongation rate of greater than <NUM>%, thereby meeting the requirements for use of this differential-strength tailor-welded component in the hot stamping field for automobiles.

To achieve the above object, the technical solution of the present invention is as follows:
A method for manufacturing a differential-strength steel welded component with an aluminum or aluminum alloy clad layer, comprising the following steps:.

Taking two straight steel plates for use as the steel plates to be welded, wherein the steel plate to be welded comprises a substrate and at least one clad layer on a surface thereof, wherein the clad layer comprises an intermetallic compound alloy layer in contact with the substrate and a metal alloy layer thereon, wherein the clad layer in a to-be-welded zone of the steel plate to be welded is not removed or thinned; wherein the two steel plates to be welded are a high-strength steel plate and a low-strength steel plate respectively, wherein the high-strength steel plate has a tensile strength of from <NUM> MPa to <NUM> MPa after hot stamping, and the low-strength steel plate has a tensile strength of from <NUM> MPa to <NUM> MPa after hot stamping;.

Presetting a butt gap between the two steel plates to be welded at <NUM>-<NUM>;.

Integrating the two steel plates to be welded by welding using a laser filler wire welding process, wherein
the laser filler wire welding process uses a laser spot having a diameter of from <NUM> to <NUM>, preferably from <NUM> to <NUM>; a defocus distance of from -<NUM> to <NUM>, preferably from -<NUM> to -<NUM>; a laser power controlled at from <NUM> kW to <NUM> kW; a welding speed controlled at from <NUM>/s to <NUM>/s, preferably from <NUM>/s to <NUM>/s; a welding wire having a diameter of from <NUM> to <NUM>, preferably from <NUM> to <NUM>; and a wire feeding speed of from <NUM>/s to <NUM>/s; wherein <NUM>% high-purity argon with a flow rate of <NUM>-<NUM>/min is used as a shielding gas; wherein a gas feeding pipe is <NUM>-<NUM> degrees relative to a welding direction and delivers the shielding gas uniformly and stably to a welding area, wherein the welding wire has a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>-<NUM>%, more preferably <NUM>-<NUM>%, Ti<<NUM>%, preferably <NUM>-<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the low-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, Si: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, more preferably <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, more preferably <NUM>-<NUM>%, Ti: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities. Preferably, the substrate of the low-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, preferably P<<NUM>%, S<<NUM>%, preferably S<<NUM>%, Al: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, Ti: <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>-<NUM>%, Ti<<NUM>%, preferably <NUM>-<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>-<NUM>%, Ti≤<NUM>%, preferably <NUM>-<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities. More preferably, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%.

Preferably, the substrates of the high-strength steel plate and the low-strength steel plate have a thickness of from <NUM> to <NUM>.

Preferably, the clad layer is pure aluminum or aluminum alloy, wherein the aluminum alloy has a composition based on weight percentage of Si: <NUM>-<NUM>%, Fe: <NUM>-<NUM>%, and a balance of Al.

Preferably, the welding is performed with the use of a welding wire having a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P≤<NUM>%, S<<NUM>%, <NUM>%≤Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities; wherein the welding wire has a diameter of <NUM>-<NUM>.

Preferably, the welding is performed with the use of a welding wire having a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P≤<NUM>%, S<<NUM>%, Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities; wherein the welding wire has a diameter of <NUM>-<NUM>. Preferably, <NUM>%≤Al<<NUM>%.

Preferably, the method further comprises a hot stamping step after the welding. Preferably, the hot stamping step comprises: subjecting a blank obtained after the welding to heat insulation at <NUM>-<NUM>, preferably <NUM>-<NUM>, for <NUM>-<NUM> minutes, preferably heat treatment for <NUM>-<NUM> minutes, followed by cooling, preferably water cooling for <NUM>-<NUM> seconds.

The differential-strength steel welded component with an aluminum or aluminum alloy clad layer obtained by the present invention is formed by butt welding of a high-strength steel plate and a low-strength steel plate, wherein the high-strength steel plate has a tensile strength of <NUM>-<NUM> MPa after hot stamping; and the low-strength steel plate has a tensile strength of <NUM>-<NUM> MPa after hot stamping, wherein the high-strength steel plate and the low-strength steel plate each comprise a substrate and at least one pure aluminum or aluminum alloy clad layer on a surface thereof, and the clad layer comprises an intermetallic compound alloy layer in contact with the substrate and a metal alloy layer thereon.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, Ti<<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the low-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, Si: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, more preferably <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, more preferably <NUM>-<NUM>%, Ti: <NUM>-<NUM>%, preferably <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, Ti<<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, and a balance of Fe and other unavoidable impurities.

Preferably, the substrate of the high-strength steel plate has a composition based on weight percentage of C: <NUM>-<NUM>%, Si: <NUM>-<NUM>%, Mn: <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, Ti≤<NUM>%, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%, and a balance of Fe and other unavoidable impurities. More preferably, B: <NUM>-<NUM>%, Cr: <NUM>-<NUM>%.

Preferably, the welding line of the differential-strength steel welded component has a tensile strength that is greater than the strength of the low-strength steel base material. If the welding joint is fractured under a tensile load, the fracture occurs in the low-strength steel base material. The welding joint has an elongation of greater than <NUM>%.

Preferably, the differential-strength steel welded component is an A-pillar, a B-pillar or a center tunnel of an automobile.

In some embodiments, the method for manufacturing a differential-strength steel welded component with an aluminum or aluminum alloy clad layer according to the present invention comprises the following steps:.

Using a cold-rolled steel plate or a steel plate with an aluminum or aluminum alloy clad layer having the above-mentioned composition as a welding blank, wherein it's ensured that the steel plate is flat, clean and free of oil and water stains;.

Keeping a butt gap between two steel plates to be edge welded at <NUM>-<NUM>;.

Using a laser filler wire welding process for the welding,
wherein the laser filler wire welding process uses a laser spot having a diameter of from <NUM> to <NUM>, preferably from <NUM> to <NUM>; a defocus distance of from -<NUM> to <NUM>, preferably from -<NUM> to -<NUM>; a laser power controlled at from <NUM> kW to <NUM> kW; a welding speed controlled at from <NUM>/s to <NUM>/s, preferably from <NUM>/s to <NUM>/s; a welding wire having a diameter of from <NUM> to <NUM>; and a wire feeding speed of from <NUM>/s to <NUM>/s; wherein <NUM>% high-purity argon with a flow rate of <NUM>-<NUM>/min is used as a shielding gas; wherein a gas feeding pipe is <NUM>-<NUM> degrees relative to a welding direction and delivers the shielding gas uniformly and stably to a welding area.

In addition, a welding wire used in the method for manufacturing a differential-strength steel welded component with an aluminum or aluminum alloy clad layer according to the present invention has a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P≤<NUM>%, S<<NUM>%, Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities; wherein the welding wire has a diameter of <NUM>-<NUM>. Preferably, <NUM>%≤Al<<NUM>%. Preferably, the welding wire having a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, preferably <NUM>≤Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities; wherein the welding wire has a diameter of <NUM>-<NUM>.

In the compositional design of the welding wire according to the present invention:
Silicon is a deoxygenating element in the welding wire. It can prevent iron from combining with oxygen and reduce iron oxide in a molten pool. However, if silicon is used alone for deoxygenation, due to the high melting point (about <NUM>) and small particle size of the resulting silicon dioxide, it's difficult for silicon dioxide particles to float and be removed from the molten pool, which leads to easy entrapment of slag in the welding line. Therefore, the weight percentage of silicon in the welding wire is controlled within the range of <NUM>-<NUM>%.

Manganese is an important hardenability element, having a great influence on the toughness of the welding line. It is also a deoxygenating element, but its deoxygenating ability is slightly lower than that of silicon. If manganese is used alone for deoxygenation, it's difficult for the resulting manganese oxide to float and be removed from the molten pool due to its high density. Therefore, silicon and manganese are used in combination in the welding wire for deoxygenation according to the present invention, so that the deoxygenation product is a composite silicate salt (MnO. SiO<NUM>) which has a lower melting point (about <NUM>) and a lower density and can aggregate into large molten slag in the molten pool. Hence, its floating is favored, and good deoxygenating effect can be achieved. In addition, manganese also has a function of desulfurization. It combines with sulfur to produce manganese sulfide, which can reduce the propensity of sulfur to cause thermal cracking. With various factors taken into consideration, the weight percentage of manganese in the welding wire according to the present invention is controlled between <NUM>-<NUM>%.

Sulfur tends to form iron sulfide in the molten pool, and iron sulfide is distributed in the grain boundary like a network. Thus, the toughness of the welding line is reduced notably. Therefore, sulfur in the welding wire is harmful, and its content must be strictly controlled. Preferably, the S content is controlled to be less than <NUM>%.

The strengthening effect of phosphorus in steel is second only to carbon. Phosphorus increases the strength and hardness of the steel. Phosphorus can also improve the corrosion resistance of the steel, but the plasticity and toughness are reduced remarkably, especially at low temperatures. Hence, phosphorus is harmful in the welding wire, and its content must be strictly controlled. Preferably, the P content is controlled to be less than or equal to <NUM>%.

Chromium can increase the strength and hardness of steel without decreasing the plasticity and toughness obviously. Chromium can increase the hardenability of the steel and has a secondary hardening effect, which can increase the hardness and wear resistance of carbon steel without embrittling the steel. Chromium can expand the γ phase region, improve the hardenability and thermal strength, reduce the temperature window in which the δ phase exists at high temperatures, promote the δ→γ phase transition, and inhibit precipitation of high temperature δ ferrite. Therefore, the weight percentage of chromium in the welding wire is controlled within <NUM>-<NUM>%.

Titanium is also a strong deoxygenating element and can form titanium nitride with nitrogen. Hence, it has a good nitrogen fixation effect and thus improves the ability of the welding line metal to resist formation of nitrogen pores. When there is an appropriate amount of titanium in the welding line structure, the welding line structure can be refined. Therefore, the weight percentage of titanium in the welding wire is controlled within <NUM>-<NUM>%.

When welding a plated plate having a preset welding gap, a welding wire comprising Mn, Cr, Ti and other elements according to the present invention is delivered to the tailor welding area to suppress the formation of high temperature δ ferrite. Manganese and chromium elements can expand the γ phase region, improve the hardenability and thermal strength, reduce the temperature window in which the δ phase region exists at high temperatures, promote the δ→γ phase transition, and inhibit precipitation of high temperature δ ferrite, so as to guarantee a high martensite conversion in the welding line structure. Titanium refines the welding line structure, improves the welding line strength after hot stamping, and guarantees the mechanical properties of the welding joint.

The carbon equivalent formula recommended by the International Institute of Welding is as follows: <MAT>.

The introduction of the welding wire will slightly increase the carbon equivalent of the welding joint, thereby ensuring the hardenability of the joint. In addition, the filling of the welding wire will further dilute the composition of the clad layer in the welding line, thereby helping to prevent formation of iron-aluminum intermetallic compounds and high-temperature ferrite phase in the welding line. At the end, it's ensured that the performances of the joint meet the requirements of the automotive industry.

When the component is welded using the method according to the present invention, the welding line of the component has a tensile strength that is greater than the strength of the low-strength steel base material after thermal forming. If the welded component is fractured under a tensile load, the fracture occurs in the low-strength steel base material.

According to the present invention, a welding wiring comprises Mn, Cr, Ti and other elements is used in combination with a high energy laser welding method. By optimizing the welding process, a welded component is obtained, wherein, after hot stamping, the welding line of the welded component has a tensile strength that is higher than the tensile strength of the base material of the low-strength steel, and an elongation rate of greater than <NUM>%, thereby meeting the requirements for use of this differential-strength welded component in the hot stamping field for automobiles.

In the method for manufacturing differential-strength steel welded component with an aluminum or aluminum alloy clad layer:.

In addition, no matter what method is used to remove or thin the clad layer in the prior art, the production speed will be slowed. With the use of the clad layer pretreatment process according to the present invention, the production efficiency can be increased by at least <NUM>%.

The direct welding according to the filler wire welding method of the present invention, without removing or thinning the clad layer of the component to be welded, guarantees the tensile strength, elongation and corrosion resistance of the welding joint after hot stamping. After the hot stamping, the tensile strength of the welding line is greater than that of the low-strength steel base material, such that if the welding joint is fractured under a tensile load, the fracture occurs in the low-strength steel base material. The welding joint has an elongation of greater than <NUM>%.

The invention will be further illustrated with reference to the following Examples and accompanying drawings.

A high-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) and a low-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) were used for tailor welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The welding wire developed by the invention was used. A laser power of <NUM> kW, a spot diameter of <NUM>, a defocus distance of -<NUM>, a welding speed of <NUM>/s, a welding wire diameter of <NUM>, and a wire feeding speed of <NUM>/s were employed. The composition of the welding wire is shown in Table <NUM>. High-purity argon was used as a shielding gas. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>; the tensile curve of the welding joint is shown in <FIG>; the fractured position is shown in <FIG>; the metallographic phase of the joint is shown in <FIG>; and the hardness of the joint is shown in <FIG>.

A high-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) and a low-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) were used for welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The welding wire developed by the invention was used. A laser power of <NUM> kW, a spot diameter of <NUM>, a defocus distance of -<NUM>, a welding speed of <NUM>/s, a welding wire diameter of <NUM>, and a wire feeding speed of <NUM>/s were employed. The composition of the welding wire is shown in Table <NUM>. High-purity argon was used as a shielding gas. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>; the tensile curve of the welding joint is shown in <FIG>; the fractured position is shown in <FIG>; and the metallographic phase of the joint is shown in <FIG>.

A high-strength hot formed steel plate with no clad layer (t=<NUM>) and a low-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) were used for tailor welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The welding wire developed by the invention was used. A laser power of <NUM> kW, a spot diameter of <NUM>, a defocus distance of -<NUM>, a welding speed of <NUM>/s, a welding wire diameter of <NUM>, and a wire feeding speed of <NUM>/s were employed. The composition of the welding wire is shown in Table <NUM>. High-purity argon was used as a shielding gas. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>.

A high-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) and a low-strength hot formed steel plate with no clad layer (t=<NUM>) were used for tailor welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The welding wire developed by the invention was used. A laser power of <NUM> kW, a spot diameter of <NUM>, a defocus distance of -<NUM>, a welding speed of <NUM>/s, a welding wire diameter of <NUM>, and a wire feeding speed of <NUM>/s were employed. The composition of the welding wire is shown in Table <NUM>. High-purity argon was used as a shielding gas. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>.

A high-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) and a low-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) were used for tailor welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The welding wire developed by the invention was used. A laser power of <NUM> kW, a spot diameter of <NUM>, a defocus distance of -<NUM>, a welding speed of <NUM>/s, a welding wire diameter of <NUM>, and a wire feeding speed of <NUM>/s were employed. The composition of the welding wire is shown in Table <NUM>. High-purity argon was used as a shielding gas. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>.

A high-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>) and a low-strength hot formed steel plate with an aluminum-silicon clad layer (t=<NUM>), which were the same as those used in Example <NUM>, were used for tailor welding. The chemical compositions of the plates are shown in Tables <NUM> and <NUM>. The steel plates were flat, and their surfaces were clean and free of oil and water stains. The to-be-welded edges of the high-strength and low-strength blanks were prepared by laser cutting. Before welding, the butt gap was preset at <NUM>. The same welding wire as that used in Example <NUM> was used. A welding current of <NUM> A, a welding voltage of <NUM> V, a welding speed of <NUM>/min, a preset gap of <NUM> between the plates to be tailor welded, and a welding wire diameter of <NUM> were employed. The shielding gas was <NUM>% argon + <NUM>% carbon dioxide. The gas flow rate was <NUM>/min. The gas feeding direction was at an angle of <NUM> degrees relative to the welding direction. After tailor welded using the welding process described above, the blanks were heated at <NUM> for <NUM> minutes and cooled in a water-passing mold for <NUM> seconds. The mechanical properties of the welding joint are shown in Table <NUM>.

Claim 1:
A method for manufacturing a differential-strength steel welded component with an aluminum or aluminum alloy clad layer, comprising the following steps:
<NUM>) Preparation before steel plate welding
Taking two straight steel plates for use as steel plates to be welded, wherein the steel plate to be welded comprises a substrate and at least one clad layer on a surface thereof, wherein the clad layer comprises an intermetallic compound alloy layer in contact with the substrate and a metal alloy layer thereon, wherein the clad layer in a to-be-welded zone of the steel plate to be welded is not removed or thinned; wherein the two steel plates to be welded are a high-strength steel plate and a low-strength steel plate respectively, wherein the high-strength steel plate has a tensile strength of from <NUM> MPa to <NUM> MPa after hot stamping, and the low-strength steel plate has a tensile strength of from <NUM> MPa to <NUM> MPa after hot stamping;
<NUM>) Presetting butt gap
Presetting a butt gap between the two steel plates to be welded at <NUM>-<NUM>;
<NUM>) Welding
Integrating the two steel plates to be welded by welding using a laser filler wire welding process, the method being characterized in that the laser filler wire welding process uses a laser spot having a diameter of from <NUM> to <NUM>, a defocus distance of from -<NUM> to <NUM>, a laser power controlled at from <NUM> kW to <NUM> kW, a welding speed controlled at from <NUM>/s to <NUM>/s, a welding wire having a diameter of from <NUM> to <NUM>, and a wire feeding speed of from <NUM>/s to <NUM>/s; wherein <NUM>% high-purity argon with a flow rate of <NUM>-<NUM>/min is used as a shielding gas; wherein a gas feeding pipe is <NUM>-<NUM> degrees relative to a welding direction and delivers the shielding gas uniformly and stably to a welding area;
wherein the welding wire has a composition based on weight percentage of C <NUM>-<NUM>%, Si <NUM>-<NUM>%, Mn <NUM>-<NUM>%, P<<NUM>%, S<<NUM>%, Al<<NUM>%, Ti <NUM>-<NUM>%, Cr <NUM>-<NUM>%, and a balance of Fe and unavoidable impurities.