Ask the Experts Metals

	Don Bowe Sr. Applications Engineer

The goal of sinter hardening is to harden the part while it’s cooling in the sintering furnace. The most important aspect is the cooling rate during the critical transformation temperature range. There are many variables that affect the cooling rate itself, including:

• Furnace dimensions
• The use of a convective gas cooling system and its blower size and heat exchanger capacity
• Furnace loading
• Part geometry (thickness), and weight
• Sintering temperature
• Length of the transition section
• Belt speed
• Atmosphere composition
• Furnace cooling capacity

Depending on the part’s alloy composition (which determines its hardenability) the critical transformation temperature range is generally between 600 and 1000 degrees Fahrenheit. To achieve transformation with lower alloy materials, you need faster cooling rates, such as 3.5 degrees Celsius/second. Changes in your furnace operating parameters, such as the part loading or belt speed, can change the cooling rate and location in the furnace where this critical temperature occurs. It is important to check your furnace temperature profile to confirm that you’re achieving acceptable cooling rates within the appropriate temperature range.

For help determining the proper cooling rate and critical transformation temperature range for your sintering furnace, contact us or call 800-654-4567 (press 1 and mention code 749).