Laser cutting is a well-established production method in the steel and metals fabrication industry. It enables complex and precise cutting of steel and aluminium sheets to a very high-quality finish which would previously have been prohibitively expensive to machine cut. It enables the manufacturer to cut small diameter holes with complex detail and good edge quality either sheet, plate, tube or box section metal items.
The process is blanketed with high pressure nitrogen as a shielding effect which eliminates oxidisation and improves edge quality and other finishing procedures. It also ensures that stainless steels do not lose its corrosion resistance and aluminium items have a burr-less finish.
By using nitrogen as your cutting gas, the laser beam melts the material, and the nitrogen blows away the molten material from the cutting groove and forces the metal to harden quickly.
Autoclaves, ovens, and curing facilities for materials such as metal, carbon fiber, Kevlar and other high-strength or pre-preg fibers are an ideal application for non-cryo nitrogen. Maintaining a dry, oxygen-free atmosphere with nitrogen generation prevents metal from oxidizing, regardless of the temperature. Resins cure more quickly, evenly, and without bubbles in the dry, low O2 atmosphere of a nitrogen inerted oven. The quick drop in O2 is provided by a properly sized surge tank, while the consistent, continuous flow of N2 gas maintains the atmosphere throughout the cycle.
During the extrusion process, two key properties of nitrogen are exploited: Nitrogen is inert to aluminium, and liquid nitrogen has excellent heat removal potential.
First, the hot section of the profile is surrounded by protective nitrogen gas. The die and extruded product are then cooled with liquid nitrogen.
Aluminium extrusion with nitrogen offers many benefits, including:
Improved surface quality: Nitrogen is inert to aluminium at extrusion temperatures. Nitrogen is applied either in liquid or gaseous form, and it forms an inert atmosphere that surrounds the section as it emerges from the die. This reduces the formation of aluminium oxide, which is typically most severe at this point (i.e., where the profile is hottest). The profile is also cooled by the nitrogen, further reducing oxidation.
Prolonged die life: Nitrogen cooling reduces die wear, and so more profiles can be extruded before the die must be repaired or replaced. This reduces costs associated with both wear-and-tear and downtime.
These stress relieving processes condition stainless steels, carbon steels and non-ferrous metals for further hardening processes. Metals are heated in a controlled atmosphere batch or continuous furnace to avoid oxidation. Nitrogen provides a suitably inert atmosphere that will help prevent exothermic reactions and dangerously overheated furnaces that would otherwise result in distorted components.
A nitrogen, hydrogen or hydrocarbon gas mixture can also be used. Hydrogen acts as a reducing agent to ensure a bright surface, while carbon controls decarburization.
Brazing is a metal joining process in which two or more metal items are joined together by melting and flowing filler material into the joint, the filler metal having a lower melting point than the adjoining metal. Nitrogen is an inert gas making it ideal for use during brazing of copper tube. During brazing, temperatures of 620°C to 790°C are required, copper will react with the oxygen in air at these temperatures to form a scale of copper oxide on the inner walls of tubing and fittings. The resulting flakes of scale dislodged in operating refrigeration systems cause system blockages and damage to components. If the air in the copper tubing being brazed is replaced with a slow steady flow of nitrogen during brazing, the formation of copper oxides can be eliminated.
This is an environmentally friendly and more easily controlled alternative to oil and salt baths. Primarily used to speed up cooling, it is widely used in vacuum furnaces but is suitable for all types of furnace. Nitrogen, hydrogen, argon and helium are suitable gases.
This process uses nitrogen to gas wipe hot-dip galvanized metals, which achieves an improved surface finish with greater uniformity of the galvanized coating. Nitrogen also minimizes zinc oxide formation in the bath, which can cause irregularities.
Carried out in several stages, each sintering stage requires a particular atmosphere. In the first instance an oxidizing atmosphere is necessary to remove lubricants. Then a reducing atmosphere is required for decarburizing and a good sintered result. Finally a reduced oxygen atmosphere is required in the cooling stage to prevent oxidation and any dullness of the metal surface, nitrogen gas provides the necessary atmosphere.
Metals and alloys can be heat treated to enhance their strength as well as resistance to wear and corrosion. These attributes are particularly important for the production of high-quality parts at competitive prices. Several heat treatment techniques utilize nitrogen for blanketing to reduce oxidation and absorb hydrogen. Some applications are outlined here:
