makes it possible to obtain a fairly fine-grained ferrite-perlite structure of steel with
equilibrium ferrite grains without perlite striation and not subject the tubes to power-
intensive heat treatment from a separate heating, i.e. produce tubes according to the
energy-saving technology.
For comparison, prior to sizing, some tubes were subjected to heating
(normalization) in a walking beam furnace at a temperature of ≈950... 1000 °С.
2. The study of microstructure and mechanical properties of tubes. It was
established that hot-rolled tubes of 06Cr1-U steel produced according to the developed
technology feature fine-grained ferrite-pearlite structure with equilibrium ferrite grains
in the size range of 15... 21 μm (No. 8-9 according to GOST 5639) with perlite content
up to 6 % and almost complete absence of perlite striation (Fig. 1 a). The structure was
more fine-grained (No. 9) in tubes made of the steel microalloyed with niobium (in
amount of 0.025%).
а
b
с
d
Figure 1. Microstructure of 06Cr1-U steel pipes:
appearance (а); SB α-α (b) and α-γ (c, d)
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