Acetylene It is also the only fuel gas hot enough to weld steel. When using our oxygen and acetylene together, flame temperatures can reach an amazing 3200°C (5792°F). You will typically use between 2 to 3 times the amount of oxygen as you would acetylene so don’t let the smaller size of our cylinder put you off. Using a number 5 welding nozzle with this gas cylinder will typically provide over 5 hours of welding time. This gas becoming increasingly difficult to source for the small user. Hobbyweld now have the rent-free answer! Combine this gas bottle with our Hobbyweld Oxygen cylinder for the perfect portable rent-free gas welding kit.