BE659612A - - Google Patents

Description

  

   <Desc / Clms Page number 1>
 



  Process for obtaining a steel with low losses in watts,
The present invention relates to a process for obtaining a steel with low losses in watts, applicable more especially to ordinary effervescent or semi-calmed mild steels.



   The value of steels with low losses in watts is well known in a number of applications, and in particular in the manufacture of strips for electric motors.



   Many processes have already been developed with a view to obtaining sheets whose losses, mainly by eddy current and by hysteresis, were sufficiently low to make these sheets technically advantageous for the applications mentioned above. These processes must, however, make use of steels of well-defined composition and are often of fairly long duration and delicate development.



   The object of the present invention is a simple process having in particular the effect of significantly reducing the losses in watts of sheets which have been subjected thereto.

 <Desc / Clms Page number 2>

 



   The process which is the subject of the present invention is essentially characterized in that the steel defined above is subjected, preferably in the form of a continuous strip, to a hot rolling operation, the final temperature of which is between Al and A3, then to a pickling operation, followed by a cold rolling operation until the final thickness is obtained, in that the strip thus cold rolled is decarburized at a temperature above Al.



   By way of example, a steel whose composition is as follows: C = - 0.02% to 0.04% - Mn = 0.300% - S 0.025% - p 0.025%, was subjected at the industrial stage to the operations resumed to the process described above, and in particular to hot rolling at final temperatures of between 830 and 780 C, and to a decarburization operation at a temperature of 800 C.



   The losses in watts, measured over a thickness of 0.5 mm, were found to be 3.5 watts / Kg at 10,000 gauss and 50 Hz.



  (The measurement was carried out by the Baby-Bpstein method on belts protruding after annealing, taken half lengthwise and half across in relation to the direction of rolling).



   The present invention applies more particularly when the end of hot rolling T is between Al and 840 C, because it has been found that, if the hot rolling is finished at a temperature above 840 C, the wattage losses suddenly drop to higher values, for example, for the same steel, from 3.5 watts to 4.25 watts / kg.



   For the same steel, it has been found advantageous, when the decarburization operation is carried out in a continuous furnace (with passage), to follow this decarburization by an annealing operation in a neutral atmosphere, at a temperature over 700 and
900 C, in order to obtain watt losses of 3.5 watts / kg, as described in the first example.



   According to an advantageous variant of the invention, @ the above process is applied to steel sheets, the composition of which in Mn and in phosphorus meets the two conditions below:

 <Desc / Clms Page number 3>

 
 EMI3.1
 0.6 mon; 1.1 '0.06%', P, 0.12
This variant has the advantage of giving the sheets a markedly increased ability to withstand subsequent cutting, punching or similar operations without deformation, and of not causing too rapid deterioration in the cutting tool.



   CLAIMS.



   1. Process for obtaining a steel with low losses in watts, characterized in that the steel defined above is subjected, preferably in the form of a continuous strip, to a hot rolling operation, the final temperature of which is included. between A1 and A3, then to a pickling operation, followed by a cold rolling operation until the final thickness is obtained, and in that the strip thus cold rolled is decarburized at a temperature above A 1.

 

Claims (1)

2. Method according to claim 1, characterized in that the temperature at the end of hot rolling is between A 1 and 840 C. 3. A method according to either of claims 1 and 2, characterized in that, when carrying out the decarburization operation in a continuous furnace (passing through), this decarburization is followed by a annealing operation in a neutral atmosphere, at a temperature between 700 C and 900 C, in order to obtain watt losses of 3.5 watts / kg. 4 A method according to either of claims 1 to 3, characterized in that it is applied to a steel whose manganese and phosphorus content meets the following two conditions: EMI3.2 0.6 z .. :: Mn. 1.1% 0.06% P 0.12%