SU473748A1 - The method of heat treatment of flat products - Google Patents

Description

The invention relates to the field of heat treatment of flat products, such as long thin plates, tires, slats, etc.

The known method of heat treatment of flat products consists in continuous - sequential surface hardening of one side and simultaneous additional heating up to the drug point and subsequent cooling of the opposite side of the product, at the same time the heating and cooling zone is relatively to the hardening zone.

However, the deformation of the product is not eliminated.

According to the proposed method, in order to reduce the warping of 1 during the surface hardening of flat products, additional heating is carried out symmetrically to the quenching zone, and the subsequent cooling is carried out until the hardenable zone reaches the initial Artensitic transformation temperature.

The method is illustrated by the drawing.

The flat product 1 is installed between the quenching inductor 2 and the heating coil 3, located on the same line, perpendicular to the longitudinal axis of the product. Behind the inductors, two sprayers 4, 5 and a baffle plate 6 are installed. The rollers 7 and S are used to fix and feed the product. To reduce the -power

the current in the coil 3, the number of its turns, as in the known case, is chosen somewhat larger than that of inductor 2. The same heating mode can be achieved in a loop double-coil

5 inductor due to the different size of the air gap between the inductive conductor and the corresponding sides of the product. The effect of reducing the distortion achieved by the proposed method can be understood based on the analysis of the auto-deformation scheme. It is known that during heating and occurs the bulk expansion of the metal. If the EC undergoes heating a layer whose thickness is commensurate with the thickness of the cold part of the metal, which corresponds to the heating of the products in question, plastic deformation of the curvature of the whole section of the product occurs under the influence of compressive internal stresses. Due to this, the convexity of the pas heated

The 0 side is retained even when the yield strength of steel at the quenching temperature drops to almost zero and the stresses are completely removed. The carried out symmetrical heating to 723 ° C of the back side of the product causes oppositely directed deformation, resulting in a uniform elongation of the heated layers with simultaneous elastic stretching of the relatively cold core. At the same time, the incrimination of the form of art is absent.

Subsequently, a sharp oxv of the event, if only one side is heated, a thin surface, now the layer quickly co: Grows, but this is prevented by deeper heated layers that cool slowly. Thus, internal stresses arise again, which at first will be stretching pl. The cooling of the deep metal slopes will cause a squeezing of the cooled surface KopKii and will create in the pressure already compressed stresses. At the same time the cooled surface Acquires a concave shape.

C1 MM: normal heating and cooling of the back side include curvature. When cooled, both sides of the product, and contract approximately equally and jointly with the core, plastically deform the heated deep layers in the axial direction, i.e., compress them. When quenched completely on martensite, which is associated with an increase in the specific volume of the metal in the quenched layer, the concavity that occurred in the known case is replaced by the convexity in the bond;

According to the proposed method, the elimination of the phenomenon of deformation; the product in the martensitic temperature range is achieved for

deceleration cooling by the quenched side, which in turn is achieved by stopping the cooling of the back side of the product at the beginning of the martsnite transformation, for example, 300 ° C. source structure-

austenite. In this case, the level of residual tensile stresses in the hardened layer turns out to be insignificant.

Subject invention

The method of heat treatment of flat products, including the continuous sequential surface hardening of one side and simultaneous additional heating of Aci with subsequent cooling of the opposite side of the product, characterized in that, in order to reduce the deformation, additional heating is performed

symmetrically to the quenching zone, and the subsequent oxjs are carried out until hardening is reached by the zone of the onset of martensitic transformation.