Ignite your business: two metalcasting facilities' approaches to heat treating are helping them stay competitive.

Extra transportation costs, added days to customer delivery, uneven service and quality due to miscommunication. Bringing heat treating in-house can help you avoid these potential job-killing dangers, as well as improve your process flow and economy.

For two metalcasting facilities that chose to offer this value-added service, delivery time to the customer was a major factor in opting to bring heat treating in-house. Transportation to outside heat treating firms can add days and weeks to lead times, and to stay competitive, delivering castings to the customer in its little time its possible is a must.

Like any process, there's no cut and dry method to running a heat treating operation. Your volume of production, type of heat treatment, and the scale and dimensions of your castings will dictate which direction to take your added service. Here, the heat treating operations of two metalcasting facilities are detailed. One firm has just started up its operation, and the other has been running one for years. One's a ductile iron shop, and the other deals with aluminum. One metalcaster chose flexibility over size, while the other depends on its unusually large furnaces to keep up its production pace. The operations are different, but the goal is the same.

Farrar's Annealing Operation

Farrar Corp., a 40-year-old ductile iron shop in Norwich, Kan., always farmed out its heat treating. Last year, however, the firm decided to set up the process onsite. The cost of transporting castings to the heat treating facility, plus the two to four days added to the schedule for shipping each way, was a big hindrance. The quality Farrar was seeing out of its heat treated castings was under par too often, which added still more days to the final delivery time.

"Sometimes we'd get a load of castings back that weren't right," said Joe Farrar, president. "And we would have to send them back again."

Farrar wanted to achieve better control of the process and reduce his lead times, so lie began to plan to bring a portion of the heat treating in-house.

"We primarily decided to do it because of slow turnaround, poor service and quality issues," he said.

Farrar Corp. had been using a heat treating facility for both annealing anti austempering treatments, but when it brought heat treating in-house, it chose only to incorporate annealing.

"The volume of austempered jobs was not high enough to justify buying tile equipment, which is more expensive," Farrar said.

More of Farrar's castings require annealing--2 million lbs. a year--and the equipment is less expensive than austempering. The metalcasting facility still put a significant investment into the process, constructing an 18,000-sq.-ft. building to house the new heat treating equipment (along with inventory) and purchasing enough equipment to handle double the initial volume of castings. The extra capacity will be used to anneal castings from other metalcasting facilities until Farrar's own production requires every furnace.

"The operation was designed to be expandable," Farrar said.

Initially, bringing heat treating in-house won't be saving Farrar money, although it won't be more expensive either. The expense of the extra capacity, plus the amount of mechanization installed, will keep the company's heat treating cost at the same level as before. Total investment in the operation was $750,000. However, the company's problem areas surrounding heat treating, such as longer lead times and poor service and quality, will be alleviated.

Farrar Corp. opted to use furnaces for 2,000-lb. loads for their flexibility. The facility's shipping containers handle the same size loads as the heat treating furnaces, so keeping track of heat treating batches and their shipments is easier. Larger furnaces are available that would have allowed Farrar to treat more castings at a time, but he is hoping that the mechanization of the operation will keep the throughput at a healthy pace. New shotblasting equipment was installed near the heat treating area, and castings are automatically transferred from the furnaces to the shotblasters, reducing labor and speeding up the throughput.

It took Farrar nine months to design and build the system, which will be in full production this month. A few new employees were hired to accommodate the extra work, but the type of work is easily trainable. Quoting customers for heat treatment on jobs won't change either, Farrar said. "We'll charge based on a per pound basis with a surcharge for the energy cost."

Stahl's Specialty: Aluminum Heat Treating

Aluminum caster, Stahl Specialty Co., Kingsville, Mo., has been heat treating its castings in-house since 1960, in large part because its volume of heat treated castings is so high, area heat treating facilities did not have furnaces big enough to process the castings at an economical price.

"The biggest furnaces that heat treating facilities near us have is 2 x 2 x 2 ft.," said Dick Kneip, sales manager. "Our furnaces are 10 x 10 x 10 ft. They charged more while only doing a fraction of the castings at a time. Plus, using outside heat treating facilities delayed delivery time to the customer."

Stahl has 28 bottom-dropping heat treat furnaces for the T-4 temper and supporting artificial aging ovens for the T-5 temper.

"Customers love it when a metalcasting facility can do everything in-house," Kneip said.

In Stahl's heat treating operation, castings are put in the T-4 furnace at about 1,000F (538C) for 10-12 hours, depending on the casting. When the cycle is over, the area below the furnace is filled with water and the castings are plunged into it. With Stahl's setup, castings go from 1,000F (538C) to 100F (38C) in 7 seconds. The quickness of this temperature change affects the quality of mechanical properties.

"The disadvantage of heat treating in house is that furnaces of this type are expensive. Each one is about $300,000," Kneip said. "You can do it for less, but you won't be able to get the temperature down as fast."

From the furnace, the castings are moved into an artificial aging oven for T-5 temper. Castings generally are in this furnace for eight hours at 340F, although exact time and temperature vary by casting.

For Stahl Specialty, which is one of the largest permanent mold aluminum metalcasters in the country, the ability to avoid transportation delays associated with farming out heat treating and customize its equipment to optimize the process has been invaluable.

With such high volumes of production (40 million lbs. of heat treated and non-heat treated castings per year), paying a heat treating facility to process its castings a handful at a time was too expensive and time consuming. Because Stahl was able to incorporate much larger furnaces in-house, it was able to provide a more economical product to its customers.

What Should I Charge?

Whether you have one furnace or 30, figuring out what to charge your customers for heat treating deserves some thought. Charging on a per-pound basis, which Farrar Corp. does, is the general method for quoting heat treating costs, but pricing isn't always cut and dry. Heat treating firm Applied Process, Livonia, Mich., calculates its pricing based on the size, shape and complexity of the casting. Steve Sumner, plant manager of Applied Process, offers the following guidelines that the iron heat treater uses in its batch processing facility.

* More small, compact parts can fit in a basket than unwieldy parts. A compact, dense part is more economical and less expensive to process than a thin, voluminous, lightweight casting.

* The higher the weight to volume ratio, the better the price.

* Required cycle time to achieve the specified properties also affects the price. Higher grades of properties require longer soak times, as do thicker castings. Prices reflect these times.

For More Information

"Heat Treating Iron Castings: Part 1," AFS Technical Dept., MODERN CASTING, May 2005, p. 70.

"Heat Treating Aluminum Castings," AFS Technical Dept., MODERN CASTING, Jan. 2005, p. 53.

"Stahl Specialty Co.: Success in Cellular Casting," A. T. Spada, MODERN CASTING, Dec. I998, p. 34.

Shannon Kruse, Senior Editor

Aluminum Heat Treatment Tempers

In order to improve dimensional stability and corrosion
resistance and enhance strength and ductility, aluminum
castings can be thermally processed by a series of heat
treating and cooling cycles involving solution, quenching and
aging. Combinations of these processes are called tempers,
which are outlined here.

T4                     T6                     T61

Solution               Solution               Solution treat,
treat and age          treat and age          quench and
naturally to a         artificially. In       age artificially
substantially          castings, T6           for maximum
stable                 commonly               hardness and
condition.             describes              strength. This
Natural                optimum                variant of T6
aging may              strength and           yields addi-
continue slowly,       ductility.             tional strength
particularly at                               and stability
elevated service                              but at reduced
temperatures,                                 ductility.
so structural
stability may not
be satisfactory.

T7                     T71

Solution treat,        Solution treat,
quench and             quench and
artificially           artificially overage
overage or             to a substantially
stabilize.             stable condition.
This temper            This temper further
improves duc-          increases thermal
tility, thermal        stability and
stability and          resistance to stress
resistance to          corrosion crack-
stress corro-          ing and reduces
sion cracking.         strength.

T5                                     Annealing

Age only. Stress relief or             Castings that have low
stabilization treatment. Cool          strength requirements but
from casting temperature and           require high dimensional
artificially age or stabilize          stability are annealed.
(without prior solution treat-         Annealing also substantially
ment). Frequently, the as-cast         reduces residual stress,
condition provides acceptable          a need in die castings.
mechanical properties but is           Annealing is a severe
accompanied by microstruc-             stabilization treatment and
tural instability or undesirable       en elevated temperature
residual stresses. Perhaps the         variant of the T5 temper.
possibility of in-service growth       Softening occurs because
is the only constraint against         annealing depletes the
using a casting in the as-cast         matrix of solutes, and the
state. In each case, the T5            precipitates formed are too
temper is appropriate.                 large to provide hardening.

Iron Heat Treatments

Ferrous Feat treatments are used to reduce residual stress and
non-uniform mechanical properties and improve strength and toughness.

Annealing                          Stress-Relieving

The austenitic matrix of cast      Used to relieve stress in the
iron is slowly cooled through      subcritical stage, minimizing
its critical temperature range,    distortion. Selecting the proper
softening the material. This       stress-relieving temperature-time
creates a ferritic                 cycle is a compromise that reduces
microstructure. If the slow        residual stress while allowing the
cooling is continued to a low      desired mechanical properties to
enough temperature, residual       be maintained in the casting.
stresses in the casting can be
relieved.

Normalizing                        Austempering

Used to obtain a higher            Castings are heated to produce an
hardness and strength.             austenitic matrix, quenched
Ferrous alloys are heated to a     rapidly to avoid the formation of
suitable temperature above the     ferrite and pearlite and held at
transformation range and then      the austempering temperature to
air-cooled to room temperature,    produce ausferrite. This produces
thus creating a                    castings that are stronger and
pearlitic structure.               tougher than conventionally heat
                                   treated iron castings.