Overview > Heat Treat

Heat Treat

Carburizing Furnace at Arrow Gear
Carburizing Furnace in Arrow's in-house Heat Treat Department.

Early in Arrow’s history, it was decided to offer in-house heat treating. Having this control helps us to ensure the metallurgical integrity of our products.

Arrow’s heat treat department, which is Nadcap certified, is equipped for a full range of heat treating operations.

In our Carburizing Furnaces, parts receive the carbon impregnated shell called Case. The Case results in gears that are extremely hard and wear resistant.

Arrow’s carburizing furnaces are equipped with gas analyzers for accurate control of the carburization process. A significant improvement from earlier methods which relied on oxygen sensors, the gas analyzers monitor such variables as carbon monoxide, carbon dioxide, carbon potential, and nitrogen in the furnace’s atmosphere. These analyzers are integrated into the operation of the furnace by their ability to control the amount of endothermic and natural gas that is fed to the furnace. This level of control leads to keeping the furnaces operating within tight tolerances, thus ensuring the metallurgical integrity of the parts.

Gas Analyzers at Arrow Gear
Gas Analyzers for Carburizing Furnaces in Arrow's in-house Heat Treat Department.

To meet a full variety of customer specifications, Arrow’s Heat Treat Department is also equipped with carburizing pit furnaces. Ideal for parts with higher mass, these furnaces are also monitored and controlled by gas analyzers which ensure that tight processing tolerances are maintained.

After leaving the hardening furnaces, some parts are quenched in one of our quench presses. Quenching involves tightly clamping the part into a precisely shaped die as it is flooded with oil – cooling it in a matter of seconds. Through this way, heat treat distortion can be minimized. For large parts, up to 36 inches, Arrow is equipped with the Dixitech DQ914 Quench Press. The Dixitech is a meticulous reproduction of a Gleason 36 inch pneumatic press, featuring the latest electronics, pumps and safety features.

Dixitech Quench Press at Arrow Gear
Arrow's Dixitech Quench Press capable of parts up to 36 inches.

Our heat treat department is also equipped with nitrogen deep freezers which are used to convert retained austenite to martinsite – a critical process for high strength steel parts used in aerospace applications.

Monitoring the quality of heat treat operations requires specialized testing. This work is performed in our Metallurgical lab.

In Arrow’s metallurgical lab, which is supervised by an on-staff, degreed metallurgist, a number of critical checks are performed to ensure the metallurgical integrity of our products.

Struers DuraScan-70 at Arrow Gear
The DuraScan-70 performing a micro hardness check on a test coupon.

Inspection for the optimal metallurgical qualities of Arrow’s heat treated parts most often begins with the preparation of test coupons. For this purpose, a test sample is made by cutting a section of the test coupon and mounting it in a hard plastic. Sometimes, depending on customer specifications, a production part will be sectioned for the mount. Next, the surface must be polished, and this is when Arrow’s Metallurgical technicians use the Struers Rotopol Polishing Machine.

A critical test is the checking of the micro hardness of parts. This test is performed on the Struers DuraScan-70. Micro hardness is checked by pressing an indenter probe into a sample of the heat treated steel. Precisely measuring the size of the resulting impression will provide the indication of the steel’s hardness in either the Knoop or Vickers scale. An integrated camera is used to document results and the system’s software provides test reports – for printing or for electronic exchange.

In measuring the hardness of the part, a critical consideration is the final carburized Case depth. This measurement determines the depth at which carbon has been impregnated into the part during the carburizing process. This Case depth must meet customer specifications to ensure the proper strength and wear resistance of the part.