Year1
- 包装：
- 标准
- 规格：
- 齐全
- 用途：
- 广泛
:-:..>.:#>Bearing steel is the steel used to make balls, rollers and bearing rings. Bearings are subjected to great pressure and friction when working, so the bearing steel is required to have high and uniform hardness and wear resistance as well as high elastic limit. The requirements for the uniformity of the chemical composition of bearing steel, the content and distribution of non-metallic inclusions, and the distribution of carbides are very strict. It is one of the most stringent steel types in all steel production.
The International Organization for Standardization
Incorporated some common bearing steel grades into international standards and divided bearing steel into: fully hardened bearing steel, surface hardened bearing steel, stainless bearing steel, high temperature bearing steel, etc. There are four categories
one steel number.
Some countries have added a category for bearing steels or alloys for special purposes. The bearing steel classification method that has been incorporated into the standard in my country corresponds to four categories: high carbon chromium bearing steel, carburized bearing steel, stainless corrosion-resistant bearing steel, and high temperature bearing steel. In the past fifty years, my country has also made great progress in bearing steel types and bearing materials such as chromium-free bearing steel, medium carbon bearing steel, special-purpose bearing steel and alloys, cermets, etc. High carbon chromium bearing steel
is the most produced bearing steel in the world. The carbon content
is about %
and the chromium content
is about .%
from
Since its birth in 2010
The main ingredients have basically remained unchanged over the years. With the advancement of science and technology, research work continues and product quality continues to improve. It accounts for more than % of the world's total bearing steel production
. So if there is no special instructions, what we call bearing steel means
.
:-:..>:#>
:-:..>.:#>Execution standards:
-r :-:. .>.:#>Main bearing steel production Laigang D
Quality Agreement that implements standards and adapts to user requirements for precision forged bearings. Among them, D
The quality requirements of the agreement are stricter than the standard
D
Requires oxygen content
, central segregation level
level, composition control, fixed length and dimensional deviation are all stricter than
standards.
Process flow:
ton
electric furnace smeltingr
ton
furnace refiningr
ton D
furnace vacuum treatmentr alloy steel rectangular billet connection Casting (
,
) r Slow cooling or hot delivery r Rolling material r Finishing r Inspection and storage.
:-:..>.:#>Quality performance:
In order to meet the above performance requirements for dynamic bearings, the following basic performance requirements are put forward for bearing steel materials:
) High Contact fatigue strength
) After heat treatment, it should have high hardness or a hardness that can meet the performance requirements of the bearing
) High wear resistance, low friction coefficient
) High elastic limit< br/>) Good impact toughness and fracture toughness
) Good dimensional stability
) Good anti-rust properties
) Good cold and hot working properties.
:-:..>:#>
.:#>Basic requirements:
Based on the above basic requirements for bearing steel, the following basic requirements are put forward for the metallurgical quality of bearing steel
br/>①Strict chemical composition requirements.
Generally, the steel used for bearings is mainly high-carbon chromium bearing steel, which contains about %
of carbon
. Hypereutectoid steel containing about %
chromium and a small amount of manganese and silicon elements. Chromium can improve heat treatment performance, improve hardenability, structural uniformity, tempering stability, and improve the anti-rust performance and grinding performance of steel.
When the chromium content exceeds
. %
After quenching, the retained austenite in the steel will increase, reduce the hardness and dimensional stability, increase the inhomogeneity of carbides, and reduce the impact toughness and fatigue strength of the steel. For this reason, the chromium content in high-carbon chromium bearing steel is generally controlled below
%
. Only by strictly controlling the chemical composition of bearing steel can we obtain the structure and hardness that meets the bearing performance through the heat treatment process.
②Higher dimensional accuracy requirements There should be higher dimensional accuracy requirements for hot-rolled annealed bars forged on high-speed heading machines.
Steel for rolling bearings requires high dimensional accuracy because most bearing parts must be pressure formed. In order to save materials and improve labor productivity, most bearing rings are forged and formed. The steel balls are formed by cold heading or hot rolling. Small-size rollers are also formed by cold heading. If the dimensional accuracy of the steel is not high, the cutting size and weight cannot be accurately calculated, and the product quality of the bearing parts cannot be guaranteed, which may also easily cause damage to equipment and molds.
③Specially strict purity requirements.
The purity of steel refers to the number of non-metallic inclusions contained in the steel. The higher the purity, the fewer non-metallic inclusions in the steel. Harmful inclusions such as oxides and silicates in bearing steel are the main reasons for early fatigue spalling of bearings and significantly reducing bearing life. In particular, brittle inclusions are most harmful because they are easy to peel off from the metal matrix during processing, seriously affecting the surface quality of bearing parts after finishing. Therefore, in order to improve the service life and reliability of the bearing, the content of inclusions in the bearing steel must be reduced.
④Strict low-magnification tissue and microscopic (high-magnification) tissue requirements.
The low-magnification structure of bearing steel refers to the general loose, centrally loose and flat microstructure (
High magnification)
The structure includes the annealed structure of steel, carbide network, band and liquid segregation wait. Carbide liquid is hard and brittle, and its hazards are the same as brittle inclusions. Reticular carbides reduce the impact toughness of steel and make it uneven in structure, making it prone to deformation and cracking during quenching. Banded carbides affect annealing and quenching and tempering structures as well as contact fatigue strength. The quality of low and high magnification structures has a great impact on the performance and service life of rolling bearings, so there are strict requirements for low and high magnification structures in bearing material standards.
⑤Specially strict requirements on surface defects and internal defects.
For bearing steel, surface defects include cracks, slag inclusions, burrs, scars, scale and other internal defects including shrinkage holes, bubbles, white spots, severe porosity and segregation. These defects have a great impact on bearing processing, bearing performance and life. It is clearly stipulated in the bearing material standards that these defects are not allowed.
⑥Strict carbide unevenness requirements.
If there is serious uneven distribution of carbides in bearing steel, it will easily cause uneven structure and hardness during the heat treatment process. The uneven structure of steel has a greater impact on the contact fatigue strength. In addition, severe carbide unevenness can easily cause cracks in bearing parts during quenching and cooling. Carbide unevenness can also lead to a reduction in the life of the bearing. Therefore, there are clear special requirements for different specifications of steel in the bearing material standards.
⑦Strict surface decarburization layer depth requirements.
In the bearing material standards, there are strict regulations on the surface decarburization layer of steel. If the surface decarburization layer exceeds the scope of the standard and is not completely removed during the processing before heat treatment, it will be damaged during the heat treatment and quenching process. It is easy to produce quenching cracks and cause parts to be scrapped.
⑧Other requirements.
In the bearing steel material standards, there are also strict requirements for the smelting method, oxygen content, annealing hardness, fracture surface, residual elements, spark inspection, delivery status, marking, etc. of the bearing steel.
Physical properties:
:-:..>.:#>The physical properties of bearing steel are mainly based on examining the microstructure, decarburization layer, non-metallic inclusions, and low-magnification structure. Generally, they are delivered by hot-rolled annealing and cold-drawn annealing. The delivery status should be stated in the contract. The low-magnification structure of steel must be free of shrinkage cavities, subcutaneous bubbles, white spots and microscopic pores. The center porosity and general porosity shall not exceed
grade. Segregation shall not exceed
grade. The annealed structure of the steel should be uniformly distributed fine-grained pearlite. The depth of the decarburization layer, non-metallic inclusions and carbide unevenness should comply with the relevant national standards.
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