▎ 摘　　要

NOVELTY - Variable-size boron-nitrogen graphene modified layer solder comprises a layer of boron graphene reinforced alloy with a thickness of 10-25 nm on the upper surface layer and a solder layer with a thickness of 50-250 mu m on the middle layer. The variable-size modified layer comprises a boron-graphene-coated foam metal layer located in the lower layer and having a thickness of 26-36 nm. The solder layer includes a silver solder sheet or a gold solder sheet, the silver solder sheet is silver copper nickel or silver copper gold nickel foil solder, the gold solder sheet is gold nickel copper boron or gold nickel palladium chromium foil tape solder, the boron-graphene-reinforced alloy layer is comprises a boron-graphene and a nickel-based alloy, the nickel-based alloy is a binary or ternary nickel-based alloy composed of nickel, palladium, gold, and copper. USE - The variable-size boron-nitrogen graphene modified layer solder is useful for the connection of high nitrogen steel and high strength steel (claimed). ADVANTAGE - The solder has a variable-scale layer, which can generate a nano-scale effect, synergistically enhances the mechanical properties of the brazing filler metal, and improves the welding strength of high-strength steel and high nitrogen steel. The tensile strength of brazed high-nitrogen steel and high-strength steel is not less than 500Mpa. DETAILED DESCRIPTION - Variable-size boron-nitrogen graphene modified layer solder comprises a layer of boron graphene reinforced alloy with a thickness of 10-25 nm on the upper surface layer and a solder layer with a thickness of 50-250 mu m on the middle layer. The variable-size modified layer comprises a boron-graphene-coated foam metal layer located in the lower layer and having a thickness of 26-36 nm. The solder layer includes a silver solder sheet or a gold solder sheet, the silver solder sheet is silver copper nickel or silver copper gold nickel foil solder, the gold solder sheet is gold nickel copper boron or gold nickel palladium chromium foil tape solder, the boron-graphene-reinforced alloy layer is comprises a boron-graphene and a nickel-based alloy, the nickel-based alloy is a binary or ternary nickel-based alloy composed of nickel, palladium, gold, and copper, the boron nitrogen graphene-coated foam metal layer is composed of boron nitrogen graphene and foam metal and the foam metal is a nickel-nickel, nickel-gold, nickel-silver, or nickel-copper binary nickel-based alloy. INDEPENDENT CLAIMS are also included for: (1) preparing the variable-size boron-nitrogen graphene modified layer solder, comprising (i) selecting silver solder sheet with silver content less than 18.5% and thickness of 150-250 mu m or gold solder sheet with gold content less than 40% and thickness of 50-100 mu m, pickling, washing, activating and drying, (ii) sputtering the bronze graphene reinforced nickel-based alloy on the upper surface of the solder sheet, (iii) vapor-depositing a boron-nitrogen graphene-coated foam metal layer on the lower surface of the solder sheet and (iv) rinsing and drying alcohol-treated solder pieces using ultrasonic waves; and (2) use of a variable-size boron-nitrogen graphene modified layer solder for the connection of high nitrogen steel and high strength steel comprises brazing under nitrogen protection, taking the variable-size boron-nitrogen graphene modified layer made of silver solder sheet to synergistically strengthen the solder, presetting the gap between high nitrogen steel or high strength steel, placing in a continuous furnace with a nitrogen atmosphere and heating to 730-920 degrees C for brazing.