An interview with Reginald "'Reg'" Roy, division manager, and Jeffrey N. Hartzheim, manufacturing manager, in which is discussed the use of polymer quenchants from Tenaxol, Inc., for heat treating of industrial cylinders.

Gentlemen, could you tell us first what are the primary products produced here at the Industrial Cylinders Company?
      Roy: Our primary products are our only products, really. The only thing this plant is designed for is the production of large high pressure cylinders for merchant gases used in industry.

Nitrogen, argon, oxygen, helium, that sort of thing?
      Roy: That's right.

You're a subsidiary of Norris Industries, Inc., Los Angeles. How do you describe the parent firm's business?
     Roy: Norris Industries cannot be described simply. In 1976, the latest year for which figures are available, net sales were slightly more than $430,000,000 coming from three basic groups -- defense products, building products, and industrial products. Overall there are 17 divisions and subsidiaries, both here and abroad, manufacturing a large variety of products ranging from decorative plumbing and hardware fixtures to automobile wheels, rims and covers.

A moment ago you mentioned large high pressure cylinders for industrial use. Does this mean you don't make smaller compressed gas cylinders such as those used for scuba diving, beverage dispensing and that sort of thing?
      Hartzheim: We don't manufacture those items here in Milwaukee, but Norris Industries has another division which does.

Is it safe to say that the cylinders used in a typical gas welding rig are representative of the type you manufacture here?
      Hartzheim: That would be a very good example. Matter of fact, the last time you saw a welder doing gas welding he could have been using cylinders from Norris Industries.

Before we get into the heat treating aspects of your operation here, would you give us a rundown of your basic manufacturing flow? First of all, what materials do you use and what forms do you start with?
      Hartzheim: We use chrome moly steel, 4130. We buy it in round corner squares typically from six inches to 71-1/2 inches in width. These are cut into pieces we call muhs which range in length depending on the weight needed for the size cylinder being produced.

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"The essence of the matter is that the people at Tenaxol were the only ones capable of helping us solve metallurgical problems, especially as they related to quenchant usage and equipment design."

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Would you run that through one more time, please?
      Hartzheim: Sure. We produce cylinders of various sizes within the overall description of "large". We know how much metal in pounds it takes to make a given size. So the squares have to be cut in whatever length it takes to provide the proper poundage.

How much variance in weight might there be then?
      Roy: The mults will weigh somewhere between 85 and 150 pounds, again, weight being a function of the finished size of the cylinder.

What happens next?
      Roy: The mults are run through an induction heating unit that brings them up to 2200°-2400°F.

One at a time?
      Roy: Oh, no. The manufacturing process is continuous, start to finish. Several muhs are going through the induction heater at any point in time.

Where do they go from the heater?
      Hartzheim: Next they are automatically positioned in a vertical hydraulic press that in one stroke forges the mult into the first phase of its cylindrical shape. Then, the shape is conveyed to a horizontal press where a mandrel pushes it, bottom end first, through a series of ring dies.

Is that the end of the basic forming then?
      Roy: Not quite. At this point the shell is about 80% of its ultimate size. The final push is cold and brings the cylinder to ultimate size. Before the cold forming, however, each shell is cleaned and lubricated. Following the final press each shell is then cut off to a finite length.

What sort of inspection is made?
      Hartzheim: At this point certified disinterested inspectors representing the U.S. Department of Transportation inspect each cylinder for internal and external defects. They also monitor the final cold forming operation. Following this, each cylinder is Measured and checked for variations in wall thickness.

Just how thick are the walls of these shells?
      Roy: Thickness specifications depend on cylinder size, but range between .187 inches and .320 inches.

When do the cylinders get to heat treating? That ought to be coming up pretty soon, shouldn't it?
      Hartzheim: After one more step. After inspection, each shell is heated at the open end, then spun-formed closed to provide rounded shoulders and neck. From there they go into the heat treating furnace.

Judging from the production rate, the furnace must be continuous, right?
      Hartzheim: Right. It's an open-flame, gas-fired unit with a cast link chain belt. The chain is our own design made especially to rotate the cylinders which go through horizontally. It operates at approximately 1600°F. Following quenching, the cylinders are tempered in another furnace.

Now, all quenching is done in polymer quenchant from Tenaxol. Would you give us a little background on how this came about?
      Roy: When Norris Industries acquired this facility in the early 1970's, it was a two-plant operation. This plant performed the basic forming, following which the cylinders were trucked to the other plant for the remaining operations, including heat treating. For a variety of reasons, operations were consolidated at this one plant which required extensive enlargement and renovation. Historically, the cylinders had been quenched in oil, being fully submerged in the process. This not only created a great deal of smoke and fire hazard, but also required that each cylinder be carefully cleaned, inside and out, prior to further processing.

Enter Tenaxol?
      Hartzheim: Not exactly enter Tenaxol. More accurately it was enter polymer quenchant. At that time we had no brand preference.

Under the assumption you're Tenaxol oriented now... 
      Roy: It's no assumption. It's simple fact.

. . . how did this favoritism develop??
      Hartzheim: We experimented with various polymer quenchants over an extended period of time. The essence of the matter is that the people at Tenaxol were the only ones capable of helping us solve metallurgical problems, especially as they related to quenchant usage and equipment design.

Could you elaborate on that?
      Roy: Well, as I'm sure you're aware, polymer quenchants are not commodities. They require a little intelligent thought and management. Otherwise, you could simply dump out oil, pour in polymer, and sail on. We understand that there are heat treaters who still claim such quenchants don't work simply because they used this approach. It could be that these quenchants don't work under certain circumstances, but then neither does oil to be precise about it. The point is, that the people at Tenaxol knew enough about heat treating and metallurgy to provide knowledgeable assistance with the overall problem.

What was the problem?
      Hartzheim: Most simply stated, in meeting required specifications, at least in terms of our production goals and rejection minimums. Metallurgically, we had the most problem in obtaining required hardness.

What did the people at Tenaxol do for you in this regard?
      Roy: Probably the primary contribution was in suggesting changes in our quench tank. It's an 800-gallon unit. We quench up to three cylinders at a time. After considerable trial and error, during which the Tenaxol people were here whenever we wished, it was determined that we weren't getting the necessary quenchant flow rate. This was due primarily to the structure of the tank... too many beams, plates and obstructions generally. Sounds simple in retrospect. But it wasn't.

Which formulation are you using?
      Hartzheim: Ucon A*, normally in a 12-14 percent concentration.

How did you arrive at this concentration?
      Hartzheim: By the experimentation procedure we just described. Through a cooling tower outside, the temperature is maintained at ll5°F on average. We check the concentration several times per day.

That's unusual. Why so often?
      Roy: In high pressure cylinder manufacture, quality control is extraordinarily important. Our standard QC unit is 200 cylinders, all serialized. Failure at any step in any of the 200 means the whole lot is failed.

Has polymer quenchant provided any other advantages?
      Hartzheim: Indeed it has. There's no fire hazard and no oil vapors caused by oil burn-off. Furthermore, the inside-outside cleaning step has been reduced.

On balance, then, how do you assess your use of these quenchants from Tenaxol?
      Roy: Well, we believe we have an efficient cylinder plant and extremely high product quality as well. Truth be told, we probably couldn't have done it without Tenaxol.

*Ucon is a trademark of Union Carbide Corp.