What Are Our Concerns About Bearings（53）

Q1:What are the alloying and performance characteristics of rolling bearing steel?

A:Representative brand GCr15, high carbon, high Cr, high hardness, good toughness

Q2:What are the matching characteristics of rolling bearing, shaft and shell hole?

A:The inner ring should rotate with the axis, so it is a transition fit or a small interference fit!  Outer ring does not turn, should be clearance with!  But the gap should not be too large, otherwise it will affect the accuracy of rotation!  

Q3:What are the advantages of rolling bearings after pretightening?

A:Select proper axial clearance for bearing preload

Q4:According to the friction properties, bearings are divided into what two kinds? What are their characteristics?

A:Rolling bearings and sliding bearings.  Rolling bearing is a general standard part, the friction coefficient is very small, only 1/10 of the sliding bearing.
Plain bearing is simple in structure, low in price and high in stiffness.  

Q5:What is the significance of bearing inner hole and shaft?

A:Bearing is a kind of support, used to support the rotation of the rotating shaft (of course, only for the common rolling bearings), reduce the friction between the shaft and the support, bearing diameter and shaft must be tightly matched.  Therefore, between the bearing inner diameter and the shaft is the base hole system, that is, the bearing inner hole is the reference hole, which is characterized by the tolerance zone of the bearing inner diameter inward contraction.  In this case, the transition fit can be used to facilitate disassembly.  Interference fit can be used in special cases.  

Q6:What is the fit interference of the bearing and shaft after the motor?  The bearing model is 6220.

A:The outer diameter of the shaft car to 100+0.00~0.01

Q7:What is the standard for forging ingot?

A:Of course, the chemical composition of the original steel ingot must meet the forging standard requirements, and the corresponding physical and chemical test inspection, forging flange processing also have to implement the flange standard, such as HG/T20592-2009.  

Q8:Are there any classification standards for forgings?

A:It can be divided into four grades: ⅰ, ⅱ, ⅲ and ⅳ  
Low alloy steel forgings for low temperature pressure vessels can be divided into three grades: ⅱ, ⅲ and ⅳ  
The selection of grade forgings by the designer according to its shape, use conditions and size, weight size, and should be indicated on the drawing (in the steel number attached to the grade symbol, such as 16Mn ⅱ).  
Then there is the difference between forging methods….  Such as free forging, die forging….  

Q9:What are the common manufacturing standards for forgings?

A:Forging commonly used manufacturing standards:  
Forgings of carbon steel and low alloy steel for JB/T4726-2000 pressure vessels  
Jb4727-2000 Low alloy steel forgings for low temperature pressure vessels  
Stainless steel forgings for pressure vessels JB4728-2000  

Q10:


What are the specific standards for forgings?

A：Forgings have many standards, different forgings product requirements are different, the standard used is also different.  And there are different standards for the same forging.  
For example, the standard of rotor forgings: JB/T1270, JB/T1265, JB/T7022, etc.  
Roller forging standard: JB3734, JB/T4120, GB/T13314, GB/T15547, etc.  
Other pressure vessel standards, nuclear power standards, gear ring standards, etc  

Q11:Which grades are forgings divided into?

A:It is divided into four grades: ⅰ, ⅱ, ⅲ and ⅳ. Low alloy steel forgings for low temperature pressure vessels are divided into three grades: ⅱ, ⅲ and ⅳ.  The selection level of forgings shall be determined by the designer according to their shape, service conditions, size and weight, and shall be indicated on the drawing (attach the grade symbol after the steel number, such as 16Mn ⅱ). 

Q12:What is the forging standard for HG20592-2009 flange?

A:It is clearly written in hG20592-2009 standard:  
JB 4726-2000 forgings of carbon steel and low alloy steel for pressure vessels  
JB 4727-2000 Forgings of carbon steel and low alloy steel for low temperature pressure vessels  
JB 4728-2000 stainless steel forgings for pressure vessels  

Q13:What standard is Jb/ T4726?

A:JB/T 4726-2010 Carbon steel and alloy steel forgings for pressure bearing equipment  
This standard specifies the technical requirements, test methods and inspection rules of carbon steel and alloy steel forgings for pressure bearing equipment.  This standard applies to carbon steel and alloy steel forgings for pressure bearing equipment whose design temperature is not less than -20℃ and design pressure is less than 100MPa.