Class 14.9 Ultra-high Strength Bolts

Hexagon Socket Head Screws, M10.0 x 80 mm, black phosphate.
Mechanical properties:
Tensile strength >1400 MPa (>200,000 PSI), 
Elongation > 7%. 
Bending angel > 60 degree

The ultra-high strength bolts' strength is beyond regular highest properties class 12.9 because of Sun Through's experience in materials and heat treatment. The durable bolt is stiff without being brittle. The bolt can be bent by more than 60 degrees. It provides great safety under huge loads. If we convert the strength to inch standard, it will be higher than Grade 9 in SAE J429.



Being too brittle is a common failure of high strength fasteners. The key is the heat treatment process. Usually, most heat treatment purposes are trying to obtain Martensite, which is a good micro-structure with extreme high hardness but low ductility. This kind of structure is not preferred when people are seeking for more impact resistance. By tempering Martensite, we can tune down hardness for a little bit in exchange of higher toughness. Tempered Martensite is obtained in most heat treatment cases, including most of class 12.9 fasteners. 


However, tempered Martensite is not enough for us. Compared to Martensite, lower Bainite has nice hardness and great impact toughness. It is an ideal structure for heavy duty applications and has low risk of hydrogen embrittlement or fatigue failure. 


However, the challenging part is, lower Bainite requires more precise control in temperature and heating/cooling time, and it needs to keep the material in certain temperature for a certain amount of time, and it takes much longer operation time than tempered Martensite.


Since Sun Through is highly skillful in heat treatment and professional in fastener manufacturing, class 14.9 bolts are no longer impossible.


If you are suffering from failure of class 12.9 fasteners, please contact us.  


*Please refer to ISO-4762 for dimensions of hex socket bolts.

*Please refer to ISO-898 (metric standard), or SAE J429 (inch standard) for details of bolting properties class or grade.


High strength bolt classification (starting from class 8.8 to 12.9) according to ISO-898-1.

Class 14.9 is refered to JIS B 1051-1976 because it is not defined in ISO.

  Class 8.8 Class 10.9 Class 12.9  

Class 14.9

(JIS Standard)

Tensile Strength


830 MPa

(120,000 psi)






Yield Strength


640 MPa 940 MPa 1100MPa   1236MPa
Elongation after fracture 12% 9% 8%   7%
HRC 23-34 32-39 39-44   40-49
Approx. equivalent to inch grade Grade 5 Grade 8 ASTM-A574   -