What metals can be tempered by a metal tempering furnace?

Metal tempering furnaces are widely used for tempering various types of metal materials, mainly including the following categories:

1. Carbon steel
Carbon steel is one of the most commonly used materials for tempering furnaces, and the balance between hardness, strength, and toughness can be adjusted through tempering.
Low carbon steel (such as Q235, 20 steel): The tempering temperature is usually 150-250 ℃ (low-temperature tempering), used to eliminate stress and improve toughness, commonly used in the manufacture of bolts, gear blanks, etc.
Medium carbon steel (such as 45 steel, 40Cr):
Medium temperature tempering (350~500 ℃): obtains a higher elastic limit, used for springs, forging dies, etc.
High temperature tempering (500~650 ℃, quenching and tempering treatment): With excellent comprehensive mechanical properties, it is used for important structural components such as shafts and gears.
High carbon steel (such as T8, T10): Low temperature tempering (150-200 ℃) retains high hardness and is used for cutting tools, measuring tools, molds, etc.

2. Alloy steel
Due to the presence of alloying elements such as Cr, Ni, Mo, V, etc., the tempering process of alloy steel needs to be adjusted accordingly to avoid problems such as “tempering brittleness”.
Alloy structural steel (such as 35CrMo, 20CrMnTi):
High temperature tempering (500~650 ℃) is used for quenching and tempering treatment to improve comprehensive performance, and is suitable for automotive gears, machine tool spindles, etc.
Some special steels require “double tempering” or “isothermal tempering” to eliminate residual austenite.
Tool steel (such as Cr12MoV, W18Cr4V):
High alloy steel (such as high-speed steel) requires “multiple high-temperature tempering (550~570 ℃)” to increase hardness through secondary hardening effect, and is used for cutting tools and cold work molds.
Stainless steel (such as 304, 420):
Austenitic stainless steel (such as 304): Tempering (stabilization treatment, 850~900 ℃) is used to eliminate intergranular corrosion tendency.
Martensitic stainless steel (such as 420): Low temperature tempering (150-200 ℃) improves corrosion resistance and toughness, used in medical devices, valves, etc.

3. Cast iron
Tempering of cast iron is mainly used to eliminate casting stress, improve processing performance, or adjust microstructure.
Gray cast iron: Stress relief annealing (500~550 ℃) reduces the tendency for deformation and cracking, used for large castings such as machine tool bed bodies and boxes.
Ductile iron: quenched and tempered (550~600 ℃) to improve strength and toughness, used for crankshafts, gears, etc.

4. Nonferrous metals and their alloys
Some non-ferrous metals improve their performance through tempering (or similar annealing processes).
Aluminum alloy (such as 2A12, 7075):
Aging treatment (similar to tempering): Artificial aging (120-200 ℃) improves hardness and strength, used for aerospace structural components.
Copper alloys (such as beryllium bronze, silicon bronze):
Tempering (aging) treatment (300-500 ℃) to strengthen alloys, used for elastic components and wear-resistant parts.
Titanium alloy (such as TC4):
Stress relief tempering (550~650 ℃) eliminates processing stress, stabilizes the structure, and is used for aircraft engine parts.

5. Special metals and composite materials
High temperature alloys (such as Inconel 718, GH4169): Tempered (aged) treatment (700~950 ℃) precipitates strengthening phases to enhance high-temperature strength, used for aircraft engine turbine blades.
Powder metallurgy materials: Tempering is used to eliminate stress during pressing and sintering processes, improve density and mechanical properties, such as powder metallurgy gears and cutting tools.
Key influencing factors of tempering process
Temperature: It determines the transformation and performance of the organization, and needs to be precisely controlled according to the material composition (for example, for every 10 ℃ increase in tempering temperature of carbon steel, the hardness decreases by about HRC 1-2).
Insulation time: Ensure uniform transformation of the organization, and extend the insulation time for large workpieces.
Cooling rate: Carbon steel can be air-cooled, while alloy steel (such as those containing Cr and Mn) may require rapid cooling (oil cooling or water cooling) to avoid temper brittleness.

Summarize
The applicability of metal tempering furnaces covers almost all industrial metal materials, and the core is to select the matching tempering temperature, insulation time, and cooling method based on the material composition, workpiece use, and performance requirements. For example:
Require high hardness cutting tools to be selected from high carbon steel and undergo low-temperature tempering;
Alloy steel quenching and tempering treatment for shafts subjected to alternating loads;
Selecting stress relief annealing for precision instrument parts reduces the risk of deformation.
In practical applications, it is necessary to combine material manuals or optimize parameters through process experiments to achieve the best treatment effect.