I had no idea. Considering what it cost, I bet it is steel.Hopefully not steel but manganin. Max recommended service temperature is 140C if you want long-term stability.
Better shunts are 0.1% accuracy and if you don't want to introduce gross error to shunt accuracy it is better to keep the temperature rather small.
For manganin shunt 50C increase causes -0.1% error to measurement.
Although Your use with cooling fan is fine.
Amazon.com: SMAKN 30A/75mV DC Current Measure Divider Shunt for AMP Meter : Electronics
Amazon.com: SMAKN 30A/75mV DC Current Measure Divider Shunt for AMP Meter : Electronics
www.amazon.com