Nitriding treatment of seamless steel pipe

Nitriding  treatment of seamless steel pipe


According to the basic principle and process characteristics of seamless steel pipe nitriding treatment, its process parameters include nitriding degree, nitriding time and ammonia decomposition rate, etc. The main point here is the relationship between temperature and decomposition rate.

Optimum relationship between nitride temperature and ammonia decomposition rate

Temperature /X	500	510	525	540	560
Decomposition rate /%	15 〜25	20 〜30	25 〜35	35 〜45	45 〜60

According to the requirement of the nitriding layer depth and hardness can be for a while, two or three paragraphs _ processing, at the same time, according to the material and technical requirements of seamless steel tube to reasonable choice, must the if line comprehensive analysis and combined with the work conditions, not to attend, to clear is seamless steel tube of heat treatment is quenched and tempered treatment.


Three nitriding processes have their own characteristics, isothermal nitriding (or called a section of nitriding) of high surface hardness HV1000 ~ 1200, small deformation, low brittleness, simple process, easy to use, but the process cycle is long, high cost, shallow infiltration layer, mostly used for shallow nitriding layer, foot, J precision, high hardness seamless steel pipe; Compared with isothermal nitriding, the surface hardness of the second stage nitriding is slightly moderate (HV850-1000), and the deformation is slightly increased, but the infiltration rate is fast. It is mostly used for seamless steel pipes with deep nitriding layer and large batch size. The nitriding rate of the third stage is fast, but the effect of hardness, brittleness and deformation is worse than that of isothermal nitriding. Therefore, when the seamless steel tube parts need nitriding treatment, the best nitriding process can be determined after comprehensive evaluation according to the technical requirements, working characteristics, production efficiency, manufacturing cost and other aspects of seamless steel tube.

It should be noted that for seamless carbon steel pipe and cast iron seamless steel pipes, in order to improve the corrosion resistance of the workpiece: I and the nitriding is called corrosion resistance nitriding, the nitriding layer depth of 0.02 ~ 0.04mm, the bead surface to form a thin and dense white nitriding layer (E phase in 0.015 ~ O.Oomm). J has the characteristics of high chemical stability. In moist air, superheated steam, sea water, gas combustion products and weak alkali solution has different corrosion resistance, corrosion resistance nitridized seamless steel pipe piano for normalizing or tempering treatment. Corrosion resistant nitriding can be used instead of nickel plating, zinc plating, bluing, polishing and other surface treatment methods, sometimes even replace alloy steel and stainless steel, etc. The process temperature of the cargo process is about 550 ~ 650°C, the time is 1 ~ 3h, the ammonia decomposition rate is 45% ~ 70%.