The repair of worn forging dies by flood-welding techniques has been around for many decades. Advances in the evolution of the process have made it a cheaper, quicker and more effective way to extend the life of die blocks and reduce tool-steel inventory costs. Today, many forging companies consider flood welding an integral part of their routine die maintenance programs.
It is arguable that no other single process or control system introduced to the forging industry has had the same economic impact potential since closed-die forging began as has flood welding. Flooding welding, or progressive manual cast welding as it is also known, is the process of streaming molten metal with electric arc into a steel alloy cavity, resulting in an impression that performs better than new.
In the Beginning
Modern closed-die forging began in 1862 at Samuel Colt’s Patent Firearms Company. Dies had a life cycle measured in re-sinks. As the impression became increasingly worn, the blocks were pulled from the hammer for re-sink. Each impression renewal brought the block closer to the scrap heap. Some forge operators keep this practice alive 155 years later.
The first recorded flood-weld repair of forging dies occurred in 1952 for Chrysler’s Detroit Forge Plant by Weld Mold Company in a small suburban Detroit shop. Founded in 1945 with the goal of reducing tooling costs in the forging industry, Weld Mold Company’s first challenge was the development of alloys that would be appropriate for the high impact energies, abrasion and temperatures that are found in hot-forging applications. A second goal was to develop a method to deposit these alloys and complete the process as quickly and efficiently as possible.
Welding in the Forge
No one seems to know when welding as a means to repair a forging die was originally introduced to the industry or how that introduction was made. It is known from our own company’s history that the weld repair of forging dies in the 1940s was done most commonly with stainless steel grades of electrodes, described as “the best we had at the time.” Some tool-and-die electrodes existed, but they were not suited to forging-die applications.
Stopgap measures at best, these repairs permitted the dies to complete production by building up worn flashlands, covering impression cracks or engineering changes. Doing a full-face re-sink was still the accepted practice for complete cavity renewal, and every forge had a die room that was constantly manufacturing new dies to replace blocks that were scrapped after three or four production cycles. The purchase of new die steel was a large part of the production budget and product cost. At one time, every forge shop had vast piles of worn, broken and obsolete forging dies and forging equipment in the yard.
By 1947, the first innovation addressing both alloy development and high-deposition welding was called the Pack Rod. Weld Mold Company’s patented Pack Rod provided deposition rates of 5-10 pounds/hour, compared to 2-4 pounds/hour of the electrodes then available. Produced by welding the bare end of the small-diameter tool-and-die electrodes to a larger-diameter (1/2-inch) core wire, leaving enough of the core exposed to be gripped in a custom electrode holder, weld deposit chemistries and characteristics could be controlled by combining different tool steels together on the Pack Rod. The time and cost of fabricating them and being limited to 14 inches in length were disadvantages that needed a solution.
Development began in 1948 on an electrode with a single-core wire with alloying contained in the flux coating. Such an electrode would be easier to use, less expensive to make and of longer length than the pack rod. Working with forging customers, the formulations and procedures were perfected by trial and error. Because these electrodes were hand-dipped well into the 1950s, production was sufficient only to supply Weld Mold Company’s needs. However, the effectiveness of the flood-welding process and products led to an increase in the number of forging companies using welded dies.
The automation of the electrode manufacturing process in 1955 by extrusion meant that, for the first time, the electrodes could be made in sufficient volume to supply the forge companies that wanted to weld for themselves. By the late 1950s, a decade after development began, true forging die-welding alloys were commercially available.
Because electrodes larger than 1/2 inch diameter x 24 inches long were hard to handle, even with custom-made long-handled holders (still called the widow-maker today), something else needed to be done. The Weld Mold ARM was developed in the mid-1950s to permit the use of electrodes up to 5/8 inch diameter and 30 inches long, and weld deposition rates had improved to 45 pounds/hour. This permitted a complete rethink of what may or may not be repairable in the forge.
Patented in 1959, the ARM is now used around the world. What would have been a scrapped hammer base or ram in 1950 is now routinely repaired. As the years progress, replacement forging components have longer lead times and higher costs. In 1965, the 3/4-inch electrode would be added to the available offerings and provide a solid 60 pounds/hour deposition rate.
Along with the high deposition rate of the Pack Rod in the 1940s and large-diameter electrodes in the 1950s, a process was needed that would take full advantage of these changing industry advances. That process, originally known as “The Weld Mold Process,” is now commonly called flood welding. When properly applied, flood welding can provide indefinite life to a forging die, improved productivity of a cavity, the ability to repair previously irreparable forging components and a reduction in the need to maintain vast inventories of die steel. These characteristics spawned an industry that even 60 years ago didn’t exist anywhere in the world except in a small shop outside of Detroit.
Since the first use of the Pack Rods, hand dipping of electrodes, invention of the ARM, extrusion of 3/4 inch baseball-bat electrodes and development of the wire manipulator, flood welding has produced predictable weld deposit chemistry suitable to the rigors of forging cavity renewal.
What began more than 75 years ago as a passion to improve the performance of tooling in the forging industry has, through trial and error, proved extremely successful. Today, many decades after that passion began to take shape, forging companies not previously exposed to the benefits of flood welding are learning to embrace the technology that many now consider an integral part of a routine die maintenance program, counting on the predictable part production at every re-sink.
Today, flood-welding materials include cored wires up to 5/32 inch diameter. When teamed with the Weld Mold Manipulator, these are also used to salvage broken forging equipment such as rams, sow blocks, hammer bases and columns. Press equipment is also reliably put back into service.
Impact on the Forging Industry
It would be an understatement to say that forge equipment and materials have morphed considerably since the time of Samuel Colt. Automation, electronics and digital thermal controls have made the process faster and more consistent. In the end, however, forged material is still formed under severe impact or pressure at high temperatures to create the final product.
The introduction of flood welding to the forging industry has had a significant effect on cost control, productivity and profitability. For the forge that properly applies it, the process and material have:
- Eliminated the need for large on-hand stocks of new die steel because dies are no longer scrapped
- Increased productivity of each cavity by as much as 300% through careful application and appropriate weld material selection
- Increased production run time, eliminating the need for multiples of even high-production cavities
- Eliminated or reduced shimming by maintaining block size and mass
- Allowed for reassignment of obsolete cavities to new purposes and maintained a footprint to the existing process
- Eliminated the requirement for full-face re-sinks because only the welded area needs to be remachined
- Made it possible to repair forging components indefinitely that at one time would have been scrapped and replaced
- Reduced tooling cost per part by 30-50% and more
All forge methods benefit from the reduction of costs and the improvement in productivity provided by the materials and processes associated with the development of flood welding. This year, a new flood-welding process will be introduced by Weld Mold that will greatly enhance flood welding.
Author David Lee is technical director at Weld Mold Company. He has been flood welding since 1991. As a welder with Federal Forge and Bharat Forge America for many years, David is intimate with the forging process and the welding equipment, materials and procedures for flood welding in the forge. He may be reached at 800-521-9755, 810-229-9521 or at firstname.lastname@example.org