Welding Fumes and Safety
A new alloy promises to lessen welders' risk of breathing toxic fumes on the job. The alloy is a welding "consumable" — the material that melts under the welder's torch to fill the gap between parts that are being joined. The new nickel alloy consumable is more expensive compared to those already on the market, but worth the cost in situations where adequate ventilation is a problem. Exposure to welding fumes can cause numerous health problems. When inhaled, welding fumes can enter the lungs, bloodstream, brain nerve cells, spinal cord and other organs and can cause both short- and long-term health effects.
Welding is the method of joining two metal parts together by applying intense heat between them, which causes the parts to melt and intermix. This process can be done directly between the two parts or through the use of an intermediate molten filler metal. The filler, base metal and base metal coating used during welding operations and the subsequent gases that are formed during the welding process release small, solid particles into the air creating welding fume.
All welding processes produce these fumes, but most fumes are produced during arc welding. In this type of welding process, high heat from an electric arc (formed between the work and an electrode) is used to melt and fuse the metal at the joint between the two parts.
The contents of the welding fumes depend on the components of the base metal, coatings and/or filler materials and the temperatures used in the welding process. Types of metals commonly found in welding fumes include aluminum, beryllium, cadmium oxides, chromium, copper, fluorides, iron oxide, lead, manganese, molybdenum, nickel, vanadium and zinc oxides. Welding fumes also produce gases, which can contain carbon monoxide, fluorine, hydrogen fluoride, nitrogen oxide and ozone.
That's why two Ohio State University engineers invented the new welding alloy.
In tests, welds made with the new consumable proved just as strong and corrosion-resistant as welds made with commercial stainless steel consumables. When melted, however, the new alloy does not produce fumes of hexavalent chromium, a toxic form of the element chromium which has been linked to cancer.
All stainless steels contain chromium, but Gerald Frankel and John Lippold, both professors of materials science and engineering at Ohio State, determined that the consumable alloy that joins stainless steel parts together doesn't have to contain the metal.
Use of the new alloy essentially eliminates hexavalent chromium in the welding fumes.
The university has three issued US patents and a pending European patent application covering a series of alloys — based on nickel and copper but with no chromium — all of which can be used with standard welding equipment.
The new alloy is expensive, however. The engineers estimated that it would cost five to 10 times more than standard welding consumables, depending on metal prices.
Frankel said that the high cost of the alloy would be justified in situations where ample ventilation may be impossible.
"I always think of someone welding a steel pipe, deep inside a ship at sea," he said. "Ventilation might not be possible, and a breathing apparatus for the welder would make working in a confined space even more difficult. In that case, using our alloy would lower the amount of ventilation needed, and help reduce costs overall."
Sometimes welders use a consumable as a bare metal wire, and other times they need to use an electrode made from a metal core coated with flux — a chemical agent that removes impurities from the weld. The Ohio State alloy works for either application.
In the laboratory, the researchers performed electrochemical tests to optimize the composition for corrosion resistance. They also performed mechanical tests of the weld joint to test the alloy's strength. The new alloy's performance was comparable to standard commercial welding consumables for stainless steel.
For further information: http://www.eurekalert.org/pub_releases/2011-02/osu-wcb021011.php