October 14, 2008
Metal fabricator Kevin Stone uses gas tungsten arc welding (GTAW) to sculpt massive pieces of art from stainless steel. Read about Stone's creative and technical processes and discover important tips that can improve your stainless steel welding.
A few years ago Kevin Stone, a senior fabricator, decided to combine his years of welding experience with his innate artistic ability and began creating stainless steel sculptures on a large scale. While people make the pilgrimage to Stone's yard in Chilliwack, B.C., to see the "Power of Flight," a 12-ft. tall, 18-ft.-long stainless steel eagle with a 41-ft. wingspan, Stone is busy inside his studio working on his latest project: an 85-ft.-long Chinese dragon.
With price tags of more than $3 million, Stone's sculptures are designed to weather the elements and never lose their shine. His objective is to create "shock and awe artwork … beauty on a large scale." To achieve this vision, he works with stainless steel, which he considers to be one of the more difficult metals to work with.
"Very few people can weld thin stainless," Stone said. "It will oxidize quickly, overheat, and burn through. It requires polishing to bring out its beauty, which is very labor-intensive. Very few people work with it. However, it's worth the effort. Once it's polished, it can be out in the elements, and it won't corrode, rust, or lose its mirrorlike quality. My vision is for my sculptures to be mounted over water to bring out the reflective qualities and use colored lights for effect."
About 14 months into the "Chinese Imperial Water Dragon" (Figure 1), Stone already has used 1,800 sq. feet of 16-gauge 304 stainless steel and expects to use another 1,800 sq. ft. before he's done.
When beginning a new sculpture, Stone conducts some preliminary research and design, but he builds primarily from his imagination. "I have a blueprint in my head that I follow," he said. "I visualize five to 10 steps ahead of what I'm working on. I picture what the overall shape will be and try to think of something that will fit inside that shape, yet be structurally strong."
To help with fit-up and save both time and material, Stone first works out the details on paper. After he finishes one piece of stainless, he cuts a piece of paper to represent the next piece and ensure it fits perfectly before transferring it to a piece of stainless.
Stone shapes the pieces by hand and then tack-welds them into place with his Miller Dynasty® gas tungsten arc welding (GTAW) machine. He first places the welds several inches apart. When Stone is happy with the fit-up, he adds more tack welds between the existing welds until there are welds about every half-inch. He eventually finish-welds the pieces together, welding a 10-in. section in one place and then moving to another section. This helps to minimize the heat input and to ensure proper fit. He finishes by grinding down the welds and polishing the pieces.
Stone had particular criteria when choosing the equipment to create his sculpture. His GTAW machine had to have a nice arc start, so he could start off slowly and still maintain good heat control. "With my sculptures, there are few welds in a flat position. I weld in the most awkward positions, conditions, and shapes you can imagine."
For the 16-ga. material he works with, Stone usually sets his machine to 160 amps and prefers a thumb control (Figure 2) rather than a foot control. He also chose a water-cooled torch because it keeps his hand cool and allows him to use a smaller torch.
Other than picking the right equipment, Stone has some advice for the aspiring metal sculptor.
"Practice your trade skills," he advised. "I have 18 years of welding experience, which allows me to weld stainless. It's not easy and takes a lot of practice.
"If you're doing any artwork, practice drawing. It helps you visualize. Drawing can actually help sculpting dramatically because it helps lock in and define your vision."
Stone also noted two common mistakes people who GTAW make. "To become steadier, many people tend to hold their breath, but this can have the opposite effect. Relax and breathe normally. Also, a gentle grip makes for a steadier hand. Hold the torch firmly but not too tightly, or fatigue will set in and lead to shaking."
When GTAW stainless, whether for a sculpture or on the job, keeping in mind a few key points can help you achieve a cosmetically appealing and sound weld.
Pulses per second (PPS) is simply how many times the machine will complete one pulsing cycle in one second. Increasing the number of pulses per second produces a smoother ripple effect in and narrows the weld bead. Reducing the number of PPS widens the weld bead. Pulsing also helps agitate the puddle and release any porosity or gas trapped in the weld.
Some beginning welders use a slow pulsing rate (perhaps 0.5 to 1 PPS) to help them develop a rhythm for adding filler metal. For welding carbon or stainless steel, use a rate of 100 to 500 PPS. Start at 100 and work upward.
High-speed pulsed GTAW (Figure 4) requires using an inverter. Conventional GTAW technology limits pulsing to a relatively narrow range of 0.25 to 10.0 PPS, whereas inverter technology enables pulsing at up to 5,000 PPS.