4results about How to "Reduce hot cracks" patented technology

The present application belongs to the technical field of preparation of multi-curved surface silicon carbide, and discloses a preparation method of reaction sintering multi-curved surface silicon carbide whole plate, comprising: mixing 100 parts of alpha-SiC powder, 15-20 parts of composite carbon source, 1-2 parts of silicon carbide fiber, 2.3-3.8 parts of dispersing agent, 8-12 parts of water-soluble phenolic resin, 2-4 parts of additive and 42-46 parts of water according to weight parts, pre-dispersing, ball-milling, spray granulating, pressing into multi-curved surface green body; the green body is stacked with graphite support parts and filled with graded silicon particles, and is subjected to step-by-step degreasing and step-by-step reaction sintering under vacuum argon, and then is cooled after temperature control to obtain the product. Through the synergistic effect of formula control of composite carbon source, specific ternary additive and fine sintering process, the technical problem of sintering cracking and cracking of multi-curved surface whole plate is eliminated, and the product density, bending strength and fracture toughness are effectively improved.

The application discloses a Cr3C2-BN nickel-based ultra-high-speed laser cladding composite coating and a preparation method thereof. In the cladding raw material powder, the mass percentage of the nickel-based powder is 65-75%, the mass percentage of the Cr3C2 powder is 20-30%, and the mass percentage of the h-BN powder is 2-10%. The main steps for preparing the coating are as follows: the three kinds of powders are uniformly mixed and then are put into a laser cladding device; and the laser cladding machine is started to perform laser cladding on a 40Cr rod material rotating appropriately with Ar gas as a protective gas. In the obtained coating, the hard phase particles are mainly Cr3C2 particles; the addition of BN promotes the melting of the Cr3C2 powder, enhances the uniformity of the coating, improves the forming quality of the coating, and generates dendritic networks around the Cr3C2 particles to optimize the mechanical structure of the coating. The coating prepared by the method has good surface morphology and excellent wear resistance and corrosion resistance; the application has simple process, excellent performance of the obtained product and is convenient for industrial application.

This invention relates to the field of casting technology and discloses a casting process for marine engine blades, comprising: preparing three types of molding sand with different compositions: surface molding sand, intermediate molding sand, and back molding sand; sequentially filling the surface of the pattern with surface molding sand, intermediate molding sand, and back molding sand using a layered compact molding method to form a gradient structure mold; introducing CO2 gas to harden the mold; applying a silica sol coating to the surface of the mold cavity; drying the surface to form a siliceous glassy film from the silica sol; pouring molten metal into the mold after closing the mold, and pouring at high temperature to decompose the organic pore-forming agent in the back molding sand to create pores in situ; and demolding after solidification and cooling to obtain the casting. This invention, through its gradient layered structure and surface sealing treatment, reduces the mold expansion rate while establishing a permeability gradient from the surface to the back layer, preventing molten metal penetration and promoting gas expulsion, effectively solving the problems of hot cracking, porosity defects, and surface sand adhesion in the casting of marine engine blades.

This invention discloses a robotic arm based on rotary friction welding and its manufacturing method. The robotic arm includes an arm body and a first flange. The arm body has a tubular structure, and the first flange is connected to the end of the arm body. The two are welded together by rotary friction welding. This invention experimentally screened 6061-T6 aluminum alloy or 7075-T6 aluminum alloy as suitable materials for the robotic arm. Through process debugging, rotary friction welding process parameters that enable reliable welding of the arm body and the first flange were obtained. This effectively solves the technical problems of insufficient strength, low precision, large welding deformation, softening of weld joints, and poor production economy in the manufacturing and application of existing industrial robotic arms. By fully utilizing the material advantages of 6061-T6 aluminum alloy or 7075-T6 aluminum alloy, the invention significantly improves the structural strength, stiffness, and fatigue performance of the robotic arm while achieving lightweight design, ensuring dimensional and assembly accuracy, and improving the structural reliability and service life of the robotic arm.