The Class 10.9 bolt is a popular flat head hexagon screw. Due to its high hardness, it is often used in applications such as precision machinery and abrasive tools. So what is the hardness of the 10.9 bolt? In this article, we will conduct a comprehensive analysis of the hardness of 10.9 class bolts, hoping to provide you with a reference. First of all, let's look at the hardness of 10.9 class bolts. According to the standard, the hardness of 10.9 class bolts should be HV320-380 or HRC34-40. In actual production, the manufacturer will soak the bolt in a quenching oil heated to 850 degrees for 30 minutes, after quenching, the bolt will be tempered for 120 minutes. This process is essential to produce the desired hardness. Next, let's take a closer look at the process of class 10.9 bolts.
Process 1 For the 35CrMo process, bolts are required to be made of 40Cr material. The bolts are 22mm in diameter and 114mm in length for truck tires. The hardness after quenching and tempering should be HV320-380 or HRC34-40, the tensile strength is 1040MPa, and the tempered sorbite is organized. Process 2 Test process 1 Using hot forging after turning, heat treatment for mesh belt furnace, quenching temperature 1-4 zone (860-870-870-860), quenching time of about 90 minutes, quenching oil cooling, hardness of HRC49-52 after quenching; The tempering temperature 1-3 zones are 510, and the hardness after tempering is HRC32-35. But the test results show that the process can not meet the requirements. In the test process 2, annealing, phosphating and cold extrusion were carried out, and the heat treatment was a net belt furnace, the quenching temperature 1-4 zones were (860-870-870-860), the quenching time was about 90 minutes, the quenching oil was cooled, and the hardness after quenching was HRC49-52. The tempering temperature 1-3 zone is 480, the hardness after tempering is HRC34-38, the tensile strength is 1005MPa, and there is a small amount of ferrite; The other tempering temperature 1-3 zones are 460, the hardness after tempering is HRC36-40, and the tensile strength is 960MPa. The whole process gives full play to the material properties and achieves the required properties. To sum up, the hardness of 10.9 class bolts on the market is usually HV320-380 or HRC34-40. For the manufacture of class 10.9 bolts, it is necessary to hold 850 degrees for 60 minutes, carbon potential 0.45, isothermal classification quenching oil, oil temperature 100 degrees, quenching time 30 minutes, tempering 480 degrees,120 minutes on the basis of. In addition, if the bolt produces a small amount of ferrite after tempering, its tensile strength is also
