Smooth hinges—Heat treatment process

Types of annealing:

1． Full annealing and isothermal annealing

Full annealing also named Recrystallization annealing , Generally referred to as annealing, this annealing is mainly used for all kinds of carbon steel and alloy steel casting component hypoeutectoid, forgings and hot rolled sections, sometimes for welded structures , the final heat treatment is usually used as a number of unimportant part , or as some parts of the pre heat treatment.

2．Spheroidizing  annealing

Spheroidizing annealing mainly used in carbon steel and alloy steel (such as the manufacture of the eutectoid steel cutting tools, measuring tools, used by die), the main purpose is to reduce the hardness, improve machinability, and prepare for the subsequent quenching.

3． Relief

annealing Stress relief annealing, also known as low temperature annealing (or high temperature tempering) ,the main annealing is used to eliminate the casting, forging, welding, hot rolling, cold drawing parts such as the residual stress. If these stresses are not eliminated, it will cause the deformation or crack of the steel after a certain period of time, or in the subsequent cutting process.

Quenching

In order to improve the hardness of the method ,the main form is through the heating , heat preservation ,cooling speed . The most commonly used cooling is salt water and oil. Brine quenching of the workpiece, easy to get high hardness and smooth surface, which is not easy to produce hardened soft spots , but it is easy to make the workpiece deformation , and even cracking. The oil used as quenching medium is only applicable to the stability of a large number of cold austenitic alloy steel or small size of carbon steel workpiece quenching.

Tempering

1． Reduce brittleness , eliminate or reduce the stress, there is a lot of stress and brittles of steel parts after quenching, if not timely tempering will often cause the deformation of steel and even crack.

2． Obtain the mechanical properties required by the workpiece, after quenching , the workpiece is of high hardness and brittleness, in order to meet the different performance requirements of different parts.

The hardness can be adjusted by appropriate tempering to reduce the brittleness, and get the toughness and plasticity.

3． Stable workpiece size

4． Some of the

alloy steels which are difficult to soften by annealing, in the quenching (or normalizing) often adopted high temperature tempering , so that the carbide in

the steel is properly assembled, so that the appropriate aggregation of carbides in the steel ,the hardness is reduced , in order to facilitatethe cutting process.

Choice of common furnace type

The furnace type shall be determined according to the different process requirements and the type of the workpiece.

1．For the batch type can’t be produced ,the workpiece is unique in size , and have many types ,requires a common process、 versatility, box type furnace can be used.

2．Heating long shaft and long wire rod , pipe and other parts , can choose the deep well type electric furnace.

3．Small batch of carburizing parts , can use

the well type gas carburizing furnace.

4．For the production of large quantities of

automobile, tractor gear and other parts of optional continuous carburizing production line or box multi-purpose furnace.

5．It is better to use the rolling furnace, roller hearth furnace for the heating mass production of stamping parts.

6．On the bulk of the stereotypes of parts , production can be used to push rod type or conveyor belt type resistance furnace.（Push rod furnace or casting belt furnace）

7．Small mechanical parts, such as : screw ,nut, such as the use of vibrating bottom furnace or net belt furnace.

8．Ball and roller heat treatment can be used in helical rotary tube furnace.

9．The non-ferrous metal ingot can be used as a push rod type furnace in mass production , and the air circulation heating furnace can be used for non-ferrous metal small and materials.

According to different structure and different materials, SMOOTH have different requirements on the hardness of heat treatment, and there are strict standards and control procedures and equipment to achieve the hinge hardness standards, so as to ensure the performance and quality of the rotating hinge test.