vacancies, the stabilization of structural state of the steel product hardened by cold
deformation is achieved. This is reflected in the increased resistance to the degradation
of the structural state under conditions of different thermomechanical operational
influences [17-21]. A decrease in the rate of softening during the heating is recorded,
which increases the fire durability of products in fire condition, and also increases the
resistance to the fatigue failure of not only the base metal but also welded connections
[21]. It is important to emphasize here that the usual common types of the heat
hardening of steel do not have such effect. If we compare some possible analogues with
a complex of the obtained properties of the cold-worked steel products, the closest is
the complex of properties of products that are hardened by the high-temperature
thermomechanical processing. In this case, it is necessary to take into account the
complexity of the technological operations – of the high-temperature
thermomechanical processing, all the previously mentioned disadvantages of the
thermal actions and
most commonly the need of using alloy steels.
The technologies for manufacturing steel products hardened by cold deformation
can be divided into several types depending on:
1)
the role of the technological deformation operation with giving the product
final geometry in the final product properties complex;
2)
the possibility of bringing the stage of preliminary hardening of the steel billet
before the technological operation of deformation;
3)
the relationship between the degree of hardening of the billet and the degree
of hardening with the necessary deformation;
4)
using or not using the technological operation of vacancy alloying, the nature
of these technological operations and their placing in the technological process;
5)
the presence or absence of a relaxation-type technological operation of the
finished cold-worked steel products.
The analysis of the existing technologies for manufacturing steel products
hardened by cold deformation – cold-worked rebars and fasteners using the cold
forging technology, and others – shows that only the technology of manufacturing
rebars can be attributed to the technology of manufacturing steel products hardened by
cold deformation. In this technology, the billet undergoes basic hardening before the
die-rolled section finish. Here, the most advanced can be the vacancy alloying using
quenching before the active cold deformation and the vacancy alloying of the finished
cold-worked product by cyclic deformation.
The existing technology for manufacturing cold-worked fasteners can be
attributed to the discussed in the work technologies only on condition that a higher
level of hardening of the finished products is obtained due to hardening of the billet by
cold deformation while maintaining technological ductility for the cold forging. In this
case, as a general situation for all cold-worked steel products with a high level of
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