JIS G4053 SCM440 Alloy Steel- SCALE STEEL.

​SCM440 is a commonly used steel for the production of high strength fasteners. The products have the advantages of stable composition, low harmful elements, high purity of steel, small decarburization layer, [SCALE STEEL]less surface defects and so on. When used, it is easy to conduct spherospherification annealing, low cold heading cracking rate, stable heat treatment quality, uniform hardness, widely used in the engine, mold and other industries.  
 
Material Name: Alloy Structural Steel  
Brand: SCM440(Japanese [SCALE STEEL]brand, see JIS G4053-2008, similar to Chinese brand 42CrMo)  
Corresponding: 42 crmo4  
Features and Scope of Application:  
It is a medium hardenability steel. After heat treatment, it has good strength and comprehensive mechanical properties, good technology and high yield.  The highest operating temperature is 427℃.  Used as steam turbine fasteners.  
 
Characteristics and Application  
1. Good quenching, deep quenching can be carried out, rather than the surface quenching of anti-saw lock on the market  
2. Less tendency to temper brittleness  
3. High temperature [SCALE STEEL]processing, beautiful after processing  
4. Good welding performance  
5 impact absorption performance is good, hammer hit up will have a rebound feeling, can not be violent damage advantages:  
(1) Good processability  
(2) Good shock absorption performance  
(3) Easy to weld  
 
Chemical Composition  
0.38 0.43 C  
Si, 0.15 to 0.35  
Mn, 0.60 to 0.85  
P 0.03 or less  
S 0.03 or less  
Cu 0.30 or less  
Ni 0.25 or less  
Cr 0.90 to 1.20  
MO, 0.15 to 0.30  
Ni 0.25 or less  
Cu 0.30 or less  
 
Mechanical properties of SCM440  
Tensile strength σb (MPa) : ≥1080(110) Yield [SCALE STEEL]strength σs (MPa) : ≥930(95)  
Elongation δ5 (%) : ≥12  
Section shrinkage rate ψ (%) : ≥45  
Impact energy Akv (J) : ≥63  
Impact toughness αkv (J/cm²)  A: 78 (8) or  
Hardness: 217 hb or less  
Sample size: sample blank size is 25mm  
 
Heat Treatment Specification and Metallographic Structure  
Heat treatment specification: 880℃,1h oil quenching, 650-680 ℃, 2H tempering, air cooling.  
Metallographic structure: tempered martensite.  
 
Heat treatment Process  
Annealing no.1 "annealing at 760±10℃, furnace cooling to 400℃ air cooling.  
HB220-230  
860±10℃ normalize, air cooling out of the oven.  
Quenching water or oil (depending on the complexity of product type), 680-700 degrees tempering.  HB<217  
Quenching oil at 840±10℃ and then tempering at 470 ℃.  HRC41-45  
Quenching oil at 840±10℃ and then tempering at 480 ℃.  HRC35-45  
Tempering +tempering No.8 quenching oil at 850℃ and tempering at 510 ℃.  HRC38-42  
Tempering +tempering No.9 [SCALE STEEL]quenching oil at 850℃ and then tempering at 500 ℃.  HRC40-43  
Tempering +tempering No.10 quenching oil at 850℃ and tempering at 510℃.  HRC36-42  
Quenching oil at 850℃ and then tempering at 560℃.  HRC32-36  
SCM440  
Oil quenching at 860℃ and tempering at 390 ℃.  HRC48-52 42 crmo round rods