Heat treatment
We can supply follows heat treatment services:
Normalizing, Annealing, Quenching, Tempering, Carburizing, Nitriding, High-frequency surface hardening and other processing services.
And we can strictly enforce the national standards.
- Pit furnace: Dia1300mm max, Length9500mm max.
- Salt bath furnace: Length1900mm max, Width1600mm max, Height900mm max.
- Trolley furnace: Legth15000mm max, Width6000mm max, Height6000mm max.
- Tunnel type continuous reheating furnace：dia30mm-dia250mm
- Induction quenching line: dia15mm-dia120mm
- Normalizing cooling fan can be used in combination of wind capacity air-cooled systems.
Quenching
Quenching is the process for making material harder.
The metal is heated to a specific temperature and rapidly cooled (quenched) in a bath of water, brine, oil, or air to increase its hardness.One drawback of using this method by itself is that the metal becomes brittle. This treatment is therefore typically followed by a tempering process which is a heating process at another lower specific temperature to stress relieve the material and minimize the brittleness problem. The temperature chosen for the tempering process directly impacts the hardness of the work piece . The higher the temperature in the tempering process, the lower the hardness.
Normalizing
Normalizing is a heat treatment process for making material softer but does not produce the uniform material properties of annealing.
A material can be normalized by heating it to a specific temperature and then letting the material cool to room temperature outside of the oven. This treatment refines the grain size and improves the uniformity of microstructure and properties of hot rolled steel.
Tempering
Tempering is a method of heat treatment used to increase the resilience of iron-based alloys such as steel. After an initial heat treatment has been done to boost the steel’s hardness, tempering then reduces some of that hardness to help improve its strength. The end result is a steel which is less brittle, with increased ductility and abrasion resistance.
Annealing
Spheroidize annealing is applicable to steels which have more than 0.8% carbon.
Parts are heated to between 1150°F and 1200°F and holding it at this temperature for a period of time to convert the microstructure. Essentially, cementite changes from a lamella formation to an alpha ferrite matrix with particles of spheroidal cementite (Fe3C). Spherodize annealing is generally done on parts which have been work hardened, to allow them to be further worked, either rolled in the case of coils, or drawn for wire. This resulting product has improved ductility and toughness with reduced hardness and strength. Spherodize annealing is normally carried out under a protective (endothermic) atmosphere to prevent oxidation and decarburization.
Spheroidize annealing is applicable to steels which have more than 0.8% carbon.
Parts are heated to between 1150°F and 1200°F and holding it at this temperature for a period of time to convert the microstructure. Essentially, cementite changes from a lamella formation to an alpha ferrite matrix with particles of spheroidal cementite (Fe3C). Spherodize annealing is generally done on parts which have been work hardened, to allow them to be further worked, either rolled in the case of coils, or drawn for wire. This resulting product has improved ductility and toughness with reduced hardness and strength. Spherodize annealing is normally carried out under a protective (endothermic) atmosphere to prevent oxidation and decarburization.
Process Annealing is used to treat work-hardened parts made out of low-Carbon steels (< 0.25% Carbon). This allows the parts to be soft enough to undergo further cold working without fracturing. Process annealing is done by raising the temperature to just below the Ferrite-Austenite region, line A1on the diagram. This temperature is about 727 ºC (1341 ºF) so heating it to about 700 ºC (1292 ºF) should suffice. This is held long enough to allow recrystallization of the ferrite phase, and then cooled in still air. Since the material stays in the same phase through out the process, the only change that occurs is the size, shape and distribution of the grain structure.This process is cheaper than either full annealing or normalizing since the material is not heated to a very high temperature or cooled in a furnace.
Full annealing is the process of slowly raising the temperature to about 50 ºC (122 ºF) above the austenite temperature line A3 or line ACM into austenite.
Full annealing is the process of slowly raising the temperature about 50 ºC (122 ºF) above the Austenitic temperature line A3 or line ACM in the case of Hypoeutectoid steels (steels with < 0.77% Carbon) and 50 ºC (122 ºF) into the Austenite-Cementite region in the case of Hypereutectoid steels (steels with > 0.77% Carbon).
It is held at this temperature for sufficient time for all the material to transform into Austenite or Austenite-Cementite as the case may be. It is then slowly cooled at the rate of about 20 ºC/hr (36 ºF/hr) in a furnace to about 50 ºC (122 ºF) into the Ferrite-Cementite range. At this point, it can be cooled in room temperature air with natural convection.
The grain structure has coarse Pearlite with ferrite or Cementite (depending on whether hypo or hyper eutectoid). The steel becomes soft and ductile.
Stress Relief Annealing is used to reduce residual stresses in large castings, welded parts and cold-formed parts. Such parts tend to have stresses due to thermal cycling or work hardening. Parts are heated to temperatures of up to 600 – 650 ºC (1112 – 1202 ºF), and held for an extended time (about 1 hour or more) and then slowly cooled in still air.