Production of molybdenum powder

Calcined ammonium paramolybdate or MoO 3 was formed by preparing a raw material powder of molybdenum metal. In industrial production, pure ammonium molybdate can be reduced directly into metal molybdenum powder in a hydrogen furnace, or it can be calcined to MoO 3 at a temperature of 550 to 650 ° C, and then reduced to metal molybdenum powder.
In the production of molybdenum products by powder metallurgy, molybdenum powder is required to have high purity, low oxygen content, and fine and uniform particle size. Production of molybdenum powder in tube or muffle furnace or kiln with hydrogen back through the secondary reduction of ammonium paramolybdate or MoO 3 is reduced to MoO 2, the second reduction at higher temperatures, the MoO 2 Reduced to metal molybdenum powder. The various reduction process parameters are listed in Tables 1 and 2. At present, some manufacturers use the direct hydrogen reduction method of ammonium paramolybdate to reduce the calcination process and avoid the impurities brought in by calcination. In order to ensure the quality of molybdenum powder, in addition to the reduction temperature, the flow rate and humidity of hydrogen, the thickness and pushing speed of the layer, and the particle size of the raw materials are all factors that affect the particle size of the molybdenum powder. Usually, the H 2 flow rate is large, and the powder having a low dew point reduction is fine, whereas the powder is coarse. Therefore, these factors must be strictly controlled in the production process to obtain a qualified powder.

  Table 1 Main parameters of primary reduction of ammonium paramolybdate

Equipment

Feeding amount kg/h  

Hydrogen flow rate m 3 /h

Furnace tube inclination (o)  

Each belt temperature, °C

1

2

3

4

5

Rotary furnace φ400/384mm

60 to 80

20 to 30  

3 to 5  

360 ~ 380

420 ~ 440

500 ~ 540

550 to 580

550 to 580

Four tube muffle furnace 260*60mm  

5kg / boat / 60min

7m 3 /h·tube

 

440

440

500

500

440

Table 2 Reduction process parameters of molybdenum in tubular furnace  

Reduction phase

equipment

Boat size mm

Loading amount g/boat

Push speed min/boat

hydrogen

Furnace temperature in each zone, °C

Flow rate m 3 /h  

Dew point °C

1

2

3

4

5

The first stage

4-tube furnace

300*60*65

250 to 280  

20

0.2 to 0.3

< -10  

 

500 to 550

 

 

11 tube furnace

250*40*35  

150 to 180

20

 

< -10  

350

450

520

540

520

second stage

11 tube furnace

250*40*35  

200 to 220

15

 

 

850

920

920

920

880

13 tube furnace

250*40*35  

250

20

0.8 to 1.0

< -10  

750

850

920

920

880

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