This welding method guarantees two of the following three attributes, not just one. This allows the welder to achieve greater penetration, higher deposition efficiency and less heat input. “The best balance match is 66% to 40% EP welding or 34% to 60% EN welding.†McQuay says, “Miller welder maximizes welding production for St. George's steel structure plant. optimize."
3. 300mm housing
When a large welding task required increased production, the St. George Steel Structure Plant had the opportunity to add four Miller Summit Arc 1250 submerged arc welder systems. This task requires a carbon steel sheet having a length × width × 12.2 m × 3.1 m × 16 mm to be made into a cylinder having a diameter of 3.7 m. The material is first sized by a plasma cutter and then wound into a large cylinder on a reel. The longitudinal seam was welded by MIG welding to form a cylindrical casing. The weld is upward, the outer weld is submerged arc welded, and then the casing is turned 180°, and the inner weld is welded to ensure 100% weld penetration.
At present, the factory uses DC submerged arc welding technology. However, due to the increased welding speed requirements, Braun and workshop chief Art Lopez intends to use a balanced adjustable AC square wave welding process in the next processing step.
In the next step, the flange of 13 to 50 mm is welded to the bottom case, and then the small flange is welded to the other three pieces. After the welding is completed, the 3 m high shell parts are joined together to form a continuous 12 m long shell.
Welds must be welded from the inside to the outside along the perimeter of each casing. To ensure this is done, the St. George processing plant is equipped with a rack system that places the cylinder on a tubular base and rotates the cylinder through a set of follower cam mechanisms that hold the cylinder Uniform angles and repetitive operation of the weld.
Such a Summit Arc 1250 welder can be used to weld both the inner weld of the casing and the outer weld of the casing. Jerry Braun has a converter that allows the welding operation to be converted between two Miller HDC 1500 control systems, RAD wire assemblies, flux funnels and OBT 1200 torches. A welded part is placed on top of the work platform, the outer weld is welded (first and last), and the other welded part is placed on the floor of the shop to weld the inner weld. The two welded parts can be oscillated at will, moving up and down to facilitate accurate positioning of the weld.
“The assembly table for the rollers, the mounting frame and the wire feed assembly guarantees the consistency of the assembly,†Braun said. “We have a welding system that guarantees the consistency of the welds. We must also make some auxiliary devices to perfect it. In addition, this The unit eliminates downtime during the conversion of the inner and outer welds. We can move an assembly station (see Figure 3), rotate it into place, and then perform the welding operation."
Figure 3 assembly
4. Save 60% welding time
Welding the flange to the housing requires welding inside and outside the cylinder (place the housing steel plate at an oblique angle and preheat the two weldments that need to be welded to 200K). Using DC EP DC positive output submerged arc welding requires 5 weld beads with an average welding speed of 0.38 m/min and a wire specification of φ4 mm AWS EM12K. Using the same welding wire, the balanced adjustable AC square wave process is used with a parameter of 66% EN+34% EP. The Summit Arc 1250 welder only needs to weld 3 channels with an average welding speed of 0.56 m/min.
It takes 60 minutes to weld a cylindrical piece with a diameter of 3.7 m at a welding speed of 0.38 m/min, while it takes at least 300 min to weld the same casing using the old DC EP process. However, in order to ensure that the interlayer temperature is not too high, the housing takes time to cool, so the actual operating time is longer. On the contrary, the balanced adjustable square wave welding process only takes 123 minutes. The operation has a small heat input and few weld beads, and there is no need to wait for the weldment to cool, and the welding dose is small.
“Excessive heat input will cause a variety of problems, such as shrinkage of the welded parts during cooling,†Braun said. “We have a housing tolerance of 1/4 inch. It sounds a bit more, but uses DC. In the welding process, if the interlayer temperature is not controlled, the flange will be far beyond the specified tolerance due to the 繺-extension phenomenon, the flange and the housing are no longer at right angles, and will never be restored again."
5. The tip of the iceberg
Due to the limited runtime of the shell project (see Figure 4), Braun and Lopez did not have time to fully explore the feasibility of the new welding system. However, the initial laboratory tests indicate a bright future. For example, using this process to join two 15mm thick steel plates, each side welded together, can achieve 100% weld penetration, while ensuring that the welding surface width is only 20mm.
“This eliminates the need for a bevel, avoids wasting welding consumables and creates excessive input,†Braun said. “We are working hard with Miller's welder experts to create a weld bead. Can achieve 100% weld penetration."
Another technology upgrade is Miller's digitally programmed HDC controller, which presets and locks 12 sets of welding programs.
“Customers regard us as experts in steel structure processing. They need high quality welding and implement quality consistency throughout the workflow. We can pre-set the operating parameters, lock them, and then we will put these parameters Putting it into the work. It will be the greatest comfort to the customer. In addition to saving operating time, the submerged arc welding technology will make our production capacity stronger, which will greatly enhance the market competitiveness of our products."
Previous page
Jiangmen Faer Sanitary Co.,Ltd , https://www.faersanitarys.com