The hot isostatic pressing technology (HIP for short) developed by Battelle Laboratory in the United States in 1955 was first used for the diffusion bonding of fuel elements in the nuclear reaction process. Based on this application, it was called “air pressure bonding” at that time. After more than 50 years of development, the hot isostatic pressing technology has been continuously expanded in the scope of application in industrial production. In the past ten years, through the improvement of hot isostatic pressing equipment, the production cost has been greatly reduced, and the application of hot isostatic pressing technology in industrial production has been broadened, and the expansion of its application scope still has great potential.
Improving the microstructure of metal materials is one of the development directions with the greatest growth potential in hot isostatic pressing. When using conventional casting techniques, segregation occurs due to the extremely long cooling time required for the alloying elements to move inward along the solidification gradient from the outer surface of the ingot or rod. At the same time, the chemical composition and microstructure of the alloy steel will be uneven. This problem is more prominent in high-alloy steel, especially high-speed steel, because there is a wider solidification interval, making heat treatment particularly difficult, and sometimes even impossible. When wrought or rolled, the final product will exhibit uneven properties. Using the combination of the spray granulation process and hot isostatic pressing process in powder metallurgy technology, the high-speed steel produced has many advantages compared with steel produced by traditional methods, such as excellent machinability, toughness, hardness, and shape stability after heat treatment.
Compared with cast high-speed steel rolls with the same composition, the high-speed steel rolls produced by the HIP process have finer and more uniform carbides, and the morphology and distribution of carbides play a decisive role in the thermal fatigue performance, spalling resistance, and toughness of the rolls, so the overall performance of HIP high-speed steel rolls is significantly better than that of cast rolls.
And in order to further improve wear resistance, HIP high-speed steel rolls can adopt higher carbon content and alloy content and still maintain good carbide morphology. When producing high-speed steel rolls with HIP technology, the roll core is generally made of cast or forged steel materials, and the high-speed steel powder used for the outer layer of the roll body is filled outside the roll core. Sintered into rolls under pressure. Since the HIP process equipment needs to withstand high pressure, limited by the equipment, the HIP process can only produce small-diameter high-speed steel rolls.
