Metal-Heat Treatment

 

 

 
 
 
 
Quench-Steel  

Quenching Process Steel

 

 

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 Quenching solutions act only are only through their ability to cool the steel. They have no beneficial chemical action on the quenched steel and in themselves impart no unusual properties.  Most requirements for quenching media are met satisfactory by water or aqueous solutions of inorganic salts such as table salt or caustic soda, or by some type of oil.  The rate of cooling is relatively rapid during quenching in brine, somewhat less rapid in water, and slow in oil.

    Brine usually is made of 5 to 10 percent solution of salt  (sodium chloride)    in water.  In addition to its greater cooling speed, brine has the ability to "throw" the scale from steel during quenching.  The cooling ability of both water and brine, particularly water, is considerably affected by their temperature.  Both should be kept cold well below 60*F.  If the volume of steel being quenched tends of raise the temperature of the bath appreciably, the quenching bath should be cooled by adding ice or by some means of refrigeration.

 Quenching solutions act only are only through their ability to cool the steel. They have no beneficial chemical action on the quenched steel and in themselves impart no unusual properties.  Most requirements for quenching media are met satisfactory by water or aqueous solutions of inorganic salts such as table salt or caustic soda, or by some type of oil.  The rate of cooling is relatively rapid during quenching in brine, somewhat less rapid in water, and slow in oil.

    Brine usually is made of 5 to 10 percent solution of salt  (sodium chloride)    in water.  In addition to its greater cooling speed, brine has the ability to "throw" the scale from steel during quenching.  The cooling ability of both water and brine, particularly water, is considerably affected by their temperature.  Both should be kept cold well below 60*F.  If the volume of steel being quenched tends of raise the temperature of the bath appreciably, the quenching bath should be cooled by adding ice or by some means of refrigeration.

 

 

Heat treatment Process

Heat Treatment Furnace

Quenching Process

Solution Heat Treatment Metal

Quenching Process Steel

 

Cooling System of Heat Treatment

Precipitation of Hardening

Heat Treatment of Titanium

Heat Treatment of Aluminum Alloy Rivet

Aluminum Alloys

Heat Treatment of Magnesium

   
 
 
 
 
 
   
 
 
 
 
 
   

 There are many specially prepared quenching oils on the market their cooling rates do not vary widely.  A straight mineral oil with a saybolt viscosity of about 100 at 100*F, is generally used.  Unlike brine and water, the oils have the greatest cooling velocity at a slightly elevated temperature about 100 to 1400*F, because of their decreased viscosity at these temperatures.

    When steel is quenched, the liquid in immediate contact with the hot surface vaporizes : this vapor reduces the rate of heat abstraction markedly.  Vigorous agitation of the steel or the use of a pressure spray quench is necessary to dislodge these vapor films and thus permit the desired rate of cooling.

    The tendency of steel to warp and crack during the quenching process is difficult to overcome because certain parts of the article cool more rapidly than others.  The following recommendations will greatly reduce warping tendency.

(1).      A part should never be thrown in to the quenching bath.  By   permitting it to lie on the bottom of the bath, it is apt to cool faster on the top side than on the bottom side, thus causing it to warp or crack.

(2).     The part should be agitated slightly to destroy the coating of vapor which might prevent it from cooling rapidly.  This allows the bath to convey its heat to the atmosphere.

(3).     Irregular-shaped parts should be immersed in such a way that the heavy end enters the bath first.

Quenching Equipment.

    The quenching tank should be of the proper size to handle the material being quenched.  Circulating pumps and coolers may be used to maintain approximately constant temperatures when a large amount of quenching is to be done.  To avoid building up a high concentration of salt in the quenching tank, provision must be made to add fresh water to the quench tank used for molten salt baths

    Tank location in reference to the heat-treating furnace is very important.   The tank should be situated to permit rapid transfer of the part from the furnace to the quenching medium.  A delay of more than a few second will, in many instances, prove detrimental to the effectiveness of the heat treatment.  When material of thin section is being heat treated, guard sheets should be emploped to retard the loss of heat during transfer to he quench tank.  A rinse tank must be provided to remove all salt from the material after quenching if the salt has not been adequately removed in the quenching tank.     

 

 

 

 

 
 
 
 
 

 

 
 
 
 
 
 
 
 

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