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die temperature [eng]

Characteristics, and temperature of the forging of some metals.

         For the successful forging of wrought, it is necessary to conduct the 'completes those with the technical criteria of interest not only to achieve the right temperature, but also the choice of materials, how to warm up and then bending them. As a general rule should be employed, especially for light alloys, the rolled bars. The materials prepared for the merger, including the 'steel, may contain cavities (or blowholes) going to affect the mechanical resistance to cracking. It is also the preferred choice of materials on the structure formed of small grains and uniformly distributed. For the purposes of 'deforming action is preferable to the press that act statically not dynamically the hammer, in other words, the' action at the press shall gradually deforming the material at a more regular stress than that imposed by the 'dynamic action in the hammer. Depending on the different materials have different temperatures of forging. The 'steel, with the' gradual increase in temperature, takes on different colors according to a range given in Table I, below. We illustrate briefly some characteristics of various metals.



         Coloration

        Temperature
             (°C)

   Red rising
   Dark Red
   Cherry red rising
   Cherry Red  
   Cherry-red light
   Light Red
   Orange 
   Yellow
   Light Yellow
   Pale Yellow
   White
   White sidereal

           650
           700
           750
           780
           800
           850
           950
         1000
         1100
         1200
         1250
         1350

     

Stainless Steel, very well is forged within wide temperature limits ranging from 900 to 1200 ° C. A good material hot deformation must not crack. May be subject to the following tests:

1) a strip of material, thickness of 20 mm, must be able to bend up to 180 ° after it is heated to 700 ° C. With the same strip, 40 mm wide and 500 long, you should be able to quickly perform four folds to 180 ° C alternate contact. The above test can also be done on rods of diameter about 16 mm;

2) a sweet piece of steel, heated to red, orange, must be able to stretch with a hammer until one and a half times its length without being produced in the cracks.

 



Steel tipology UNI

Forging temperature
in °C


Max.


Min.

Simple


UNI 6783-71
Fe 37; Fe 42; Fe 50 ..



1200

 

900

 

Casehardened

 

UNI 5332-64

C 10

C 16

16 NiCr 11

12 NiCr 3

20 CrNi 4

18 NiCrMo 5

 

 

 

1150

1150

1100

1100

1100

1100

 

 

900

900

900

900

900

900

Hardened

 

UNI 5332-64

C 20; C30

C 40; C50

35 CrMo 4

30 CrMo 4

35 NiCr 9

38 NiCrMo 4

30 NiCrMo 12

40 NiCrMo  7

 

 

 

1150

1100

1100

1100

1100

1100

1100

1100

 

 

850

850

850

850

900

900

900

900

     Hard steel, is forged wing temperature of 900 - 1100 ° C. It 'requires that the heating occurs slowly, because it is too fast creates internal tensions which then can cause cracks you tempera. For all types of steel have to reach the maximum temperature indicated, the temperature limits must be strictly controlled. the aim is also to get the maximum plasticity. And 'good rule to remove the metal from the heat immediately when it has reached a temperature of forging. after plastic deformation is necessary to 'heat treatment process to improve the characteristics of the material, as instructed by the manufacturers of steel.

       
Stainless steel, no particular difficulty in forging the types of low carbon (0.10 to 0.40%), while the hardest types, with rates of more than 0.4% carbon, the 'operation is more delicate. It must be done in 'range,
900 ° - 1200 ° according to the types, after a slow pre-heating up to 800 ° c. The cooling after forging, must be done slowly to avoid tensions and splits.

       
Copper is forged around 700 - 900 ° C. If it is cooled abruptly gets more sweetness, so that they can deform even when cold, this makes it hard to return to work hardening. The tests to determine the quality of the copper can made empirically cold in the following ways:

1) a ring with a hole of 20 mm, outer diameter 60 mm, 30 mm width of the corridor should be able to zoom in with a tapered pin ø 40 mm max, forced into the hole until you get

2) a cylinder with a diameter equal to half the height it must trace up to 1 / 3 's initial height;

3) a fine pitch threaded rod you have to bend up to 180 degrees, in contact, without breaking. 

Brass, if you have the title of zinc by 35-48% good hot deformed at a temperature of about 650 - 750 ° C, if you want sweet, since it work hardens easily, you have to anneal to form a 550 to 580 ° C for 30-60 min and cool it in water. example of leaded brass forging suitable: 60 + 39% Cu% Pb% Zn + 1 (UNI 7279-74), and the brass rail: 60% Cu + 40% Zn. In general, not to alter the characteristics of the alloy, heating the pieces must be slowly and progressively in non-oxidizing environment. A rapid heating causes a discontinuity in the metal mass, because the crystals have not had time to change from a structure to 'other. To heat the pieces you can use a flame or electric ovens, provided subject to the following standards:

- With respect to temperature;

- Non-oxidizing heating;

Heating-slow and progressive.

        
Bronze, d 'can forge aluminum at 700 ° C. (Wrought copper alloys. Bronzi binary tin. Chemical composition 2527/1a-74 UNI).

        
Light alloys, after buying a forged high mechanical strength. The heating of the billets is preferable to electric furnaces for the greater possibility of a thermal control. As the temperature forging of light alloys rarely exceeds 500 ° C, heating is also performed with salt-bath furnaces or those bath 'air.
       
As a rule, the ingots cast alloy must be extruded or rolled prior to forging, in order to allow the particulate material to become compact and cohesive.
       
Sometimes, for lack of machinery for the extrusion is directly forge the ingot casting. To give the material a good plasticity hot, you make the molding or shaping the hydraulic or pneumatic and the hammer instead. In fact the press functions with a moderate rate of work, so the movement of the pasty mass is so sweet and continuous. Conversely, the hammer acts brutally to the material, causing the disintegration of the molecular structure. all 'beginning of the deformation must always act gently, step by step you can proceed with greater speed, until the material has achieved greater cohesion and can withstand subsequent processing including the hammer.

 

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