Heating tubes are formed by inserting electric heating wires into seamless metal tubes (carbon steel, titanium, stainless steel, copper), filling the voids with magnesium oxide powder for excellent thermal conductivity and insulation, and then shrinking the tube. They are then processed into various shapes as required by the customer. They feature simple structure, high thermal efficiency, good mechanical strength, and excellent adaptability to harsh environments. They are suitable for heating various liquids and acidic, alkaline, and saline solutions, and also for melting metals with low melting points (lead, zinc, tin, bismuth alloys).