This paper is adapted from article published by BMR Group in Metal Center News, October 1995, Page 95
A little known, but highly effective, technique for heat treating can turn the art of surface hardening into an almost science while it saves you BIG money.
Heat treating is a time-honored method of hardening metal surfaces; the surface is heated to an appropriate temperature, then allowed to cool rapidly to produce a surface much harder than the interior of the part However, there are two major problems, according to Boyd Machine & Repair Co. (BMR) Wolf Lake, Indiana, it is difficult to control the area affected by the process, and the stresses generated in the part may deform it. Here’s a case in point.
SOME PROOF
When Steel Warehouse Co. in South Bend, Indiana, found itself with a very short lead time for a new take-up mandrel on its pickling line, the company knew it couldn’t afford any mistakes. Its specifications called for case hardening the mandrel face and the grip area to prevent damage to the coils coming off the line. Steel Warehouse was concerned that conventional heat treating processes would warp the segments of the mandrel. If that happened, the parts would have to be scrapped resulting in material cost overruns and putting the company far behind its production schedule.
With no time for failure and no tolerance for additional costs on the project, Steel Warehouse turned to BMR, one of the BMR Group of Companies, to have the mandrel surface hardened by laser heat treating. BMR provides laser heat treating services in addition to machining and fabrication of large specialized components for a number of industries in the Midwest. It has been using a Spectra-Physics 975 5kW CO2 laser for surface hardening of high-value components for the steel processing industry since about 1986.
Boyd Machine has a history of aggressive R&D efforts to find new ways to meet unique needs, such as thermal-sprayed coatings of metallics, ceramics, and carbides as well as plasma welding. Steel Warehouse was attracted to BMR because of its laser heat treating capability, according to Larry Boyd, the company’s owner and very-much-involved president.
That makes Steel Warehouse a little unusual, because, according to Boyd, most companies aren’t aware of the benefits of laser heat treating. “The people at Steel Warehouse knew exactly what they needed and they knew the advantages of laser heat treating over conventional methods when they came to us,” says Boyd. He claims that a recent marketing study he conducted identified numerous applications for laser heat treating in the steel processing industry, but also disclosed that many companies had never heard of this application of laser technology
Duane Leake, an operations manager at Steel Warehouse, in charge of getting the mandrel built and installed, says the decision to use laser heat treating was easy. “We had a six-week schedule and we couldn’t afford to be late. [Laser heat treating] took away the risk of distortion that can occur with flame hardening. The laser heat treating [approach] helped us stay on schedule.”
SOLVING THE PROBLEMS
BMR treated the entire surface area of the four-segment mandrel as well as the grip area. According to Leake, it is the mandrel’s surface area that is most likely to be damaged by mill-edge steel coils. The rough edges and burrs on the steel coil can gouge and gall a mandrel surface after only a few days of operation.
When the mandrel surface is gouged, it causes a condition known as friction gouging on the coils being processed. Within a few weeks many mandrels can damage the material so severely that the inner 10 ft. of the coil has to be scrapped. The grip area also can become damaged after repeated strikes by the end of the coil, allowing the rolled coil to slip after the mandrel has expanded and begun to turn. This slippage can damage a significant amount of the coil and cause other problems on the line.
By laser heat treating these key areas of its mandrel, Steel Warehouse plans to save a significant amount of its product from being scrapped, avoid certain common maintenance costs, and keep its line running more. Leake plans to use laser heat treating on the next mandrel the company builds. “I don’t see why everyone isn’t doing this with their mandrel surfaces and grip areas,” he says.
Of course, Larry Boyd agrees whole-heartedly. It’s companies like Steel Warehouse, looking for technologies to give them an edge, that have become the core of BMR’s heat treating business. Boyd says his customers in the steel processing industry bring him a variety of parts. Some of the more common projects are the tapered seats on arbors, some of which can be 10 feet long and 15 inches in diameter, as well as flattening rolls, which can also be 10 feet long and as much as 60 in. in diameter. He says these parts are virtually impossible to heat treat by conventional methods without some distortion.
Boyd feels the three major advantages of laser heat treating are reduced scrap costs caused by parts distorted during treatment elimination of post-treatment machining, and application of hardening only in pre-determined wear areas. Companies that are sensitive to these problems with their heat treated parts are good candidates for laser heat treating services.
BOYD’S START-UP WAS TOUGH
But BMR’s entry into the heat treating market has not been easy When he bought the laser, Boyd planned to use it primarily as a research tool to find new ways to strengthen components his customers were building for their markets. BMR has provided carbonizing services for a long time and has developed a reputation as a premier supplier of coating services among many companies in steel processing.
“Being an engineer by training, I figured everyone would see the advantages of laser heat treating right away,” says Boyd.
But he was constantly challenged to prove me value of the laser as a viable heat treating method every time he talked with someone about it. So few people had knowledge of the application that he had to spend much of his time explaining the physics of laser hardening instead of promoting its benefits.
In addition to having to become an emissary for the unique application, Boyd, ran against one of the more pragmatic obstacles facing today’s marketers. Most companies Boyd approached had customer-certified processes already in place that they were unable or unwilling to change. “Everyone seemed to think the technology was promising and would give them a better product but no one wanted to change their existing process, even if it saved them money.”
Worse still for Boyd, many of his customers didn’t want their competitors to gain access to the same benefits, so Boyd couldn’t even tell new prospects about all the different things he was doing with the laser. That deprived him of the word-of-mouth advertising that normally launches such a high-value service into heavy demand.
But after initiating a direct marketing campaign among a select list of prospects, he found the best applications for laser heat treating were right in the industries he’d been serving with other technologies and services.
“Once we began our direct mailings, we started seeing a lot of new applications from people who had never heard of the technology before, but knew they needed it,” notes Boyd. “After that we recognized the laser was really just another component in the mix of services we already offer as a specialized component fabricator and repair shop.” He says the components he gets most frequently for laser heat treating are steel rolls, large shafts, and slitting arbors.
SELECTIVE APPLICATIONS
It isn’t that end-use products generally can’t benefit from laser heat treating; it’s that some products lend themselves better to the technology For example, because laser heat treating works by moving the part slowly under the laser beam, there is a practical limitation to the speed with which parts can be treated by laser. As a result laser heat treating is not cost competitive for some components with high production volumes. Although BMR has two CNC workstations that share the laser beam, throughput is almost always a bottleneck with a laser heat treating setup.
Further, parts that are very inexpensive or are not subject to distortion are frequently not good candidates for laser heat treating. The more sensitive the customer is to distortion of the part and the more valuable the part is, the more likely the customer is to rely on laser heat treating. Boyd points out that the cost of post-treatment machining and the cost of scrap caused during heat treating make the laser the only feasible heat treating option for many components.
Parts that are not well suited for laser hardening still may benefit from carbide coating or even from conventional heat treating processes. And Boyd says he doesn’t hesitate to funnel work to conventional treaters. “We’re in business to help our customers make money The results of heat treating are pretty much similar among the different technologies,” he says. “The big difference is the scrap and additional machining requirements that conventional methods create.”
If a customer is better off with a different heat treating technology or a different surface hardening method, Boyd says he doesn’t hesitate to recommend the better approach, because the laser needs to stay dedicated for the most critical applications.
While BMR is serving an expanding base of laser heat treating customers, president Boyd is not resting on his success. “I guess I’m the kind of guy who’s always looking for some new R&D application,” he admits. And so, he’s looking at adding another plasma welding machine to the arsenal of special tools and capabilities he offers to the steel processing industry.
