L298H board with Stepper motor Heat problem

Using Arduino Motors, Mechanics, Power and CNC
3

MarkT:
You drive the motor with 18V and it gets hot - so what voltage is the motor meant for??

Its 24V i can upload the tech spec of the motor when i get home. 8)

The motor: http://www.nmbtc.com/pdf/motors/PM35S-048-HHC6.pdf

And my code:

#include <Stepper.h>

// change this to the number of steps on your motor
#define STEPS 300

// create an instance of the stepper class, specifying
// the number of steps of the motor and the pins it's
// attached to
 Stepper stepper(STEPS, 8, 9, 10, 11);

void setup()
{
   // set the speed of the motor to 30 RPMs
   stepper.setSpeed(100);
}

void loop()
{
   
   stepper.step(3000);
   
delay(1000);

 
   stepper.step(-3000);
   
delay(1000);  
}