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Machines & equipment for sale

RGB Metallurgical Ltd Vacuum Furnace

Stock No
OX1880
Model
Vacuum Heat Treatments Furnace
Year of Manufacture
Recon 2013
New or Used
Used (Second Hand)
Internal Size (WxDxH mm)
Chamber Ø430 x 700 (Basket 2202 x 600)
Max Temp
1350°C
Other Info
Rebuilt and upgraded in 2013
Location
Our Central Warehouse, Aldridge, UK
External Dimensions (WxDxH mm)
2660 x 2300 x 2350

Description

Wentgate Vacuum Furnace

For hardening, tempering, brazing and special advanced processes

During February and March 2013 a full refurbishment and upgrade of the WENTGATE VACUUM HEAT TREATMENT FURNACE was completed at a cost in excess of £120,000. The furnace was installed primarily for heat treating various components manufactured by Materials Solutions for Rolls Royce Ltd Under AMS 2750E specifications. As a heat treating furnace, it was designed to operate and be capable at temperatures between the ranges of 600 - 750°C to AMS 2750E class 2 + or - 6°C and 750°C to 1350°C AMS 2750E class 4 + or - 10°C

The vacuum furnace comprises the following major components:-

  • Double skinned water cooled vacuum vessel
  • Double skinned water cooled bolted door
  • Large soft start star-delta gas fan motor
  • Integral copper heat exchanger packs in the rear of the hot zone
  • Water cooling manifold for water flow control
  • Fully automatic integrated control cabinet
  • A two stage pump set comprising Edwards“roughing” pump and a final vapour diffusion pump
  • Heating via a power transformer with phase angle firing solid state thyristor
  • Flanged and hinged furnace door which opens sufficiently to allow complete and unobstructed access to the hot zone
  • Fully automatic PLC control ensuring reproducible cycles and product quality.
  • Efficient gas fan cooling and efficient multi-directional twin inert gas flow within the hot zone
  • Removable steel hot zone lined with Graphite composite board and insulation, graphitic elements and hangers and moving graphitic lined front/door bung which opens during the quenching operation.
  • Process recording and data logging facilities to comply with AMS 2750 E.
  • Model no TD 80W/HA 100kW Air blast heat exchanger for integral cooling water supply. 2600 x 1700 x 1570 mm, 363 kg.
  • Break recirculation tank for cooled water storage, 2750 x 1820 x 1770 mm
  • Work charge loading trolley.

General Operation

Loading the Furnace

Using the loading baskets or similar, the load to be treated should be set up on the loading trolley forks using a stacked basket arrangement. It is important to ensure that the load is evenly distributed across the baskets and vertically through the load to ensure good temperature uniformity and passage of the quench gas through the stack.

The furnace control system may be fitted with a “Guaranteed Soak” feature which requires the embedding of TWO trailing thermocouples within the load at strategic points which will represent the extremes of temperature within the load. It may be possible to set the acceptable differential temperature between these thermocouples (Control panel Cycle Menu “G” setting) before the soak time at hardening or tempering temperature commences. 

Selecting and starting the cycle

Upon initial startup wait 30-50 minutes for the diffusion pump to heat up and then select the programme required. Select the Programme recipe screen. and modify and select the required programme number. When ready press “Cycle Start” to run the cycle. Multiple screens are available and can be scrolled to observe different functions; such as valve positions, cycle status and alarms.The valve screen can be selected which gives a status of the vacuum valves and the position of interlocking valves which will change when the standby situation changes to cycle situation and high vacuum valve open etc.

Once the cycle start is initiated the interlock valve to the furnace opens and the pump starts to evacuate the furnace chamber. This results in the large Bourdon vacuum gauge to the left of the furnace door starting to show the formation of a vacuum indicated by the anti-clockwise movement of the dial finger. The Edwards digital vacuum gauge on the panel will also start to show a fall in pressure. 

Assuming all is satisfactory, the roughing pump will now continue to pump down the chamber to a level of approximately 8 x 10² (8 mBar) and at this point the Diff pump will engage. The vacuum level will continue to fall quite quickly and at this point the diffusion pump sealing plate will lift making the pump part of the furnace pumping system. The vacuum level will continue to fall to eventually reach the high vacuum region.

There is a facility to select evacuation time in the cycle menu (1st option) and this time is that required between the diffusion pump becoming active and the start of heating. This can be varied to ensure that the lowest vacuum possible is reached before heating starts (normally about 45 minutes). The furnace temperature will rise at a rate as set in the programme (normally about 5 Deg C /min). 

At a temperature programmed into the cycle as Partial Pressure, the partial pressure solenoid will open and Argon is leaked into the furnace in a controlled manner by way of a solenoid valve. This will bring the vacuum up to a lower level and should show about 3.2 X 10² (3.2 mBar) as shown on the digital vacuum gauge on the panel. The furnace will automatically control at this set point.

This is used to avoid sublimation of alloy constituents such as Chromium in the product being treated as the process is both temperature and vacuum related; higher vacuums create greater sublimation.

Once soaking at hardening temperature is complete, as timed from the point at which the difference in temperature between the two comparison
thermocouples is within the selected “G” soak parameters, the furnace will go into quench mode.

The High water flow through the heat exchangers will start and simultaneously the top and bottom bungs will open, the furnace will be isolated from the pumps via the interlock valve and Nitrogen will back fill the furnace to the selected pressure in the programme. Once this pressure has been reached the cooling fan will start. 

Cooling will continue to the programmed set point and the chamber pressure automatically adjusted to remain at the set point. A further time to end of cycle can be put into programme to ensure that the load is uniformly at the prescribed finishing temperature.

If a temper cycle has been requested in the programme, then the furnace will automatically go through a pressure relief and pump down routine as for the hardening cycle , the cycle will vent and then continue automatically into the tempering cycle, after which normal cycle end will ensue.

When the cycle is completed as shown by automatic back fill (3 x 10+3 on the digital vacuum gauge and zero on the Burdon gauge) and water flow returned to either >65 Deg C flows or <65 Deg flows and heating off.

The red cycle stop button is pressed and the back fill button on the side of the furnace pressed to equalise furnace with atmospheric pressure. The red cycle stop button is then pressed again so that the door locking mechanism can be removed.  The furnace door can then be opened and the load removed.

Electrical

  • The main heating supply is 440 Volts 3 phase 50 hz supply primary and 90 volts secondary.
  • Control panel. This is multi voltage. 440 V 3 phase, 110 volts single phase, and 24 volts ac system.
  • Furnace heating is 40kW per phase configured in Delta and controlled by phase angle firing thyristor. 
  • Please note that the incoming power from the distribution boards is not a single, but three separate supplies. 

NOTE A full installation, re-commissioning and training package is available from the original on-site engineers RGB Metallurgical Ltd

pdf icon Print / Download RGB Metallurgical Ltd Vacuum Furnace Datasheet

Additional files

Photographs taken prior refurbishment. Our refurbishment service is not available on all machines.