Where the fasteners for securing machinery and structural parts are concerned, Grade 12.9 hex head bolts stand out due to their strength, durability, and reliability. In the following paragraphs, learn about the material, mechanical properties, applications, advantages, and a detailed FAQ section about Grade 12.9 hex head bolts.

What are Grade 12.9 Hex Head Bolts?

Class 12.9 hex head bolts are extremely strong fasteners. They often apply to applications where superior performance and reliability are required. The “12.9” in bolt designation refers to tensile strength, meaning that the bolt must have a minimum tensile strength of 1200 MPa and yield strength of 1080 MPa. These individual fasteners are identified by their hexagonal heads through which fasteners can easily be installed and withdrawn using standard tools. 

Composition of the Materials

Grade 12.9 bolts are normally made from alloy steel material, that is, carbon steel alloyed with various elements such as manganese, molybdenum and nickel. This improves the bolt’s mechanical properties due to which it can be utilized under conditions of high stress. 

Normally, material composition includes the following: 

Carbon (C): Up to 0.40% 

Silicon (Si): Up to 0.40% 

Manganese (Mn): 0.60% to 0.90%

Molybdenum (Mo): 0.15% to 0.30%

Nickel (Ni): 0.40% to 0.70%

A common process in heat treatment is quenching and tempering. As a result, grade 12.9 provides significant strength.

Mechanical Properties

The mechanical properties of the Grade 12.9 bolts play a major role in successful high level applications. Those include:

Tensile Strength: Greater than or equal to 1200 MPa (Mega Pascals, which is the maximum tensile stress material can undergo without breakage.

Yield Strength: At least 1080 MPa, stress at which the bolt will deform permanently.

Elongation: Generally about 8-10%, amount by which bolt will extend before breaking.

Hardness: Typically measured on the Rockwell scale, usually, grade 12.9 has a hardness between 33-39 HRC (Rockwell Hardness Scale).

All these properties make bolts Grade 12.9 the best to use in many demanding environments: Both automotive and aerospace industries, among others within the construction area.

Applications of 12.9 Grade Hex Head Bolts

The 12.9 grade hex head bolts can be found in a variety of applications:

Automotive: Assemblies include engine, chassis, and suspension systems.

Aerospace: Applications where strength-to-weight ratio is essential in structural members

Construction: Heavy machinery, cranes, and structural members

Manufacturing: Equipment assembly where there is a need for strength fasteners in order to maintain stability and safety.

Higher Strength: Bolts Grade 12.9 have strength greater than that of the lower grades and hence are used for applications where loads are heavy.

Resistance to Wear, Fatigue, and Corrosion: The Bolts have high resistance against wear, fatigue, and corrosion due to which they can be used for long durations.

Versatility: The wide variety of sizes and lengths makes Grade 12.9 Bolts useful in many fields.