SU1579679A1 - Method of reconditioning rolling mill rolls - Google Patents

Abstract

The invention relates to rolling production and can be used to restore the rolling rolls of hot and cold rolling mills. The purpose of the invention is to increase the service life of the roll by reducing the oxygen content in the deposited layer. The method consists in the following: during the restoration of the rolling rolls, mechanical removal of defects, preliminary and concurrent heating, surfacing of the wear-resistant layer with subsequent thermal and mechanical treatment of the roll barrel are performed. At the same time around the roll 1 before surfacing create a protective atmosphere due to the heating by gas burners 2 with partial combustion of gas. The air flow rate with respect to the gas flow is determined by the ratio V air / V gas = 1.12 + 0.304. 10 -3T n, where T n - the heating temperature of the roll, ° C. The method allows to avoid increased oxygen content in the most loaded surface area of the roll barrel, which increases the service life of the mill rolls. 3 ill., 1 tab.

Description

Mathematical processing of the calculated data results in obtaining the dependence of the air flow in relation to the gas flow on the required heating temperature.

 1.12 + 0.304- Yu-X

Vrai

where Tn is the heating temperature of the roll, ° C. The method is carried out as follows (Fig. 3).

The roll 1 is heated by gas burners 2, made in the form of pipes along the roll barrel, into which a mixture of air and methane is supplied in an amount determined depending on the desired heating temperature. In the case of incomplete combustion, a protective atmosphere of CO-CO2- - H2-H2O-N2 is formed, which, rising

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(due to high temperature) between the roller and the thermocasing 3, protects the surface of the roller from oxidation and exits in the upper zone, where the welding process is carried out with the guides of the welding head 4.

Example. Turning of a barrel of a worn support roll of the mill 2000 is performed. The roll diameter is 1600 mm, weight is 41 tons, material 9HF. Then the roller is heated to 420 ° C. To do this, the ratio between air and methane is determined using the indicated formula, the ratio is 1.257. Heating is carried out for 24 hours. At the end of the surfacing, the roll is practically not oxidized, in some places the color of the roll is blue, which corresponds to a very thin oxide film A. 20C in flow

17 days with a three-shift operation of the equipment. Wire diameter 5 mm. Surfacing mode: current 500 A, voltage on the arc 33 V, speed 36 m / h. After surfacing, tempering is performed: heating to 500 ° C, holding for 4 hours and slow cooling at a rate of 30 ° C per hour (in a thermostatic method). After complete cooling, they are mechanically processed and filled into a cage. The table shows the operational characteristics of the rolls, restored by the proposed (option 2) and by the known (option 1) methods.

As can be seen from the table, the roll restored by the proposed method (option 2) has the highest performance and durability due to the low oxygen content in the weld metal. When the amount of air decreases as compared to the calculated one (option 3), more CO and H2 (reducing agents) are present in the composition of the atmosphere, i.e. there is no oxidation, as in option 1, and therefore a positive effect (roll durability) does not rises. Therefore, reducing the amount of air compared to the amount of gas is impractical. In the case when the air flow is excessive (option 4), an oxidizing atmosphere is formed, under the influence of which the roll barrel is covered with thick dross, the oxygen of which passes into the seam,

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as a result, the durability of the roll is reduced.

Claims (1)

The technical and economic advantages of the proposed method of reducing the rolling rolls are that using the proposed method avoids an increased oxygen content in the most loaded surface area of the roll barrel, thereby increasing the operational durability of the rolling rolls and, consequently, reducing the annual need for rolls. Invention Formula A method of restoring rolls, including mechanical removal of defects, preliminary and concomitant heating, surfacing a wear-resistant layer with subsequent heat and mechanical treatment of the roll barrel, characterized in that, in order to increase the service life of the roll by reducing the oxygen content in the weld metal, a protective roll is created around the roll atmosphere, heating a roll with a gas flame with partial combustion of methane, and the air flow 1,} (m3) in relation to the consumption of methane Vria (m3) is determined by the ratio m 1.12 + 0.304.10-3H, Vrai where Tk is the heating temperature of the roll, ° C. By a known method 1.25 1.17 1.35 0.6 Weld metal chipping Barrel wear roll Also Vykroshka on overlaid to metal 20 & 300C ifl (fc SQO ° C 0.2 600 ° C 700 ° C 800 ° C 90Qt WOO ° C 1100 ° C 12QO ° C WJO ° C moec OM0.60.8 H20 / H2 Phys. 1