The L298 is not really suitable for driving stepper motors. You should look at, for example, the Pololu A4988 stepper motor driver board. It is much easier to use with the Arduino and because it can limit the current in the motor it can take a much higher voltage.
The A4988 is probably not quite capable of supplying the full current for your motor. You would be better with a driver with a higher current capability, but they may be considerably more expensive.
...R
PS the Pololu DRV8825 may be a bit better. ...R