* If you are having trouble viewing this e-mail, click here.
* To make sure you continue to receive our e-mails in your inbox (not sent to bulk or junk folders), please add newsletter@vacaeronews.com to your address book. Click here for more information.
* To log on to the VAC AERO web site, please click here.
|
December 2008 |
905-827-4171 |
|
|
|
|
|
|
VAC AERO to Add Fourth Large Vacuum Oil Quench Furnace
|
|
|
VAC AERO will be installing another large vacuum oil quench furnace which will be the fourth such furnace in operation at its Oakville, Ontario Thermal Processing facility.
The new furnace is required to accommodate the continuing strong demand for VAC AERO's vacuum oil quench process. It will be used for vacuum hardening of large aircraft landing gear components and other high strength steel components. The new furnace is a VAC AERO Model VAV 7272-VOQ that will be designed and built by VAC AERO's Furnace Manufacturing Division. It is expected to be commissioned by the 4th quarter of 2009. To complement the new oil quench furnace, additional parts washing and tempering capabilities have already been installed. READ MORE
|
|
|
Maintenance Procedures for Vacuum Furnaces Part 4 - Leak Rate Testing
|
 |
Vacuum level as indicated by vacuum gauge readings is not always a true indication of the actual conditions within a vacuum furnace. It is possible to have two identical furnaces operating at the same pressure but producing entirely different results on heat treating.
The reason for this can be explained by the relative leak tightness or leak rate of each furnace. Most furnaces are equipped with pumping systems sufficient to overcome reasonably significant leaks. On the furnace with the higher leak rate, air would be leaking continuously into the furnace resulting in a higher residual oxygen content than in the leak tight furnace. The higher oxygen content would adversely affect the heat treating results. Therefore, leak rate checks as prescribed by the furnace manufacturer should be performed at regular intervals to prevent this problem. READ MORE
This is the last in a series of four articles on Vacuum Furnace Maintenance. (read part 1) / (read part 2) / (read part 3) |
|
|
Vacuum Brazing Techniques Part 4 - Vacuum Brazing Cycles
|
 |
There are a number of factors that influence the development of a brazing cycle. These include such things as base metal and braze alloy composition, mass of the assembly and joint design.
However, each cycle is comprised of a number of common segments. The illustration below shows the typical profile for a vacuum brazing cycle. During the initial pumpdown, water vapour adsorbed by the parts and furnace is driven off. For most brazing applications, a pumpdown before heating to a vacuum level of 8 x 10-4 torr or better is recommended. A vacuum safety interlock should be programmed into the cycle to ensure this level is reached. After pumpdown, the initial heating rate should not exceed 15ºC (30ºF) per minute. Faster rates may cause paste braze alloy to spall off or distortion of the assembly. Heating continues to a stand off temperature at about 25ºC (50ºF) below the solidus temperature of the braze alloy. The load is then soaked at this temperature to ensure temperature uniformity and to allow vacuum levels to recover. A soak time of 30 minutes is usually sufficient, though the incorporation of a second vacuum safety interlock in the braze cycle program may be desirable. READ MORE
This is the last in a series of four articles on Vacuum Brazing Tecniques. (read part 1) / (read part 2) / (read part 3) |
|
|
|
