Powder Metallurgy Technology
Overview: The production process of high-speed steel by powder metallurgy is mainly divided into two steps:
1.The basic principle of gas atomization powder production is to restrict the flow of molten high-speed steel through the guide tube at the bottom of the crucible, and then flow out at a certain flow rate, and atomize it into a certain size distribution powder with high-pressure argon or pure nitrogen.
2.Powder molding, after sieving and pre-compacting, under high temperature (1100 degrees Celsius) and high pressure (100MPa), hot isostatic pressing is consolidated and densified into a near-final shaped blank or is first prepared into a billet and then processed by machining Into the final shape. This process effectively solves the problem of eutectic segregation of coarse carbides produced in ingots during general smelting of high-speed steel, and a fine and uniform crystal structure is obtained.
Advantages: The powder metallurgy high-speed steel has a fine structure, and its strength and toughness are respectively 2 times and 2.5 to 3 times that of smelted high-speed steel; high strength, good dimensional stability after heat treatment, good processing performance, high hardness, and good wear resistance. The high-temperature thermal hardness is also improved by HRC1～2 than that of smelted high-speed steel. The physical and mechanical properties are highly isotropic, and the quenching deformation is small; the wear resistance is increased by 20% to 30%; the heat treatment yield is high and the economic benefits are good; , There are great advantages in complex props.
Disadvantages: The production process of powdered high-speed steel is too cumbersome and the process is long. Generally, it needs to go through powdering-screening-pressing-sintering, which is high in cost and expensive; in addition, it also has problems such as complex preparation process, serious powder oxidation, and difficulty in preparing large billets.
Injection Molding Technology
Overview: Injection molding is an advanced technology that uses rapid solidification to prepare high-performance materials. Spray-formed high-speed steel also belongs to powder metallurgy high-speed steel. This technology eliminates the problem of macro-segregation of components and has the organizational characteristics of powder metallurgy.
Advantages: The spray forming process is a metallurgical technology that combines the advantages of traditional casting and powder metallurgy, as follows:
• Small and uniform organization;
• Compared with the traditional process, the spray forming process can tolerate more impurity elements;
• The process flow is short, the yield is high, and the cost is low;
• Low degree of oxidation
Disadvantages: There is always a certain amount of looseness in the as-deposited blank, but it can usually be completely sealed by extrusion, hot and cold rolling or hot isostatic pressing, and the efficiency of the final product is significantly lower than 100%; material loss comes from:
• Overspray of droplets
• Droplets or particles bounce off the surface of the blank
• Detection of scrap or processing loss and removal of the substrate and top of the blank
• Scrap due to metallurgical quality problems.
Post time: Sep-02-2021