Patent Application
20210262070
The present invention relates to metallurgy, in particular to structural alloyed cast steel suitable for use in railway engineering, in particular in the railway car manufacturing industry.
With the development of railway engineering, more and more attention is devoted to the development of improved structural materials with increased reliability and durability, which are at the same time relatively inexpensive. Such materials find their use in construction of above ground railways and manufacturing of various parts of the railway rolling stock. Further, the strictest requirements in terms of service reliability are imposed on steel used for railway rails and parts of freight and passenger car trucks, particularly for parts requiring durability and wear resistance, such as center plate discs, wheels and axles of car trucks, friction wedges and friction plates.
A friction wedge for freight car trucks is a part of the shock absorber of the car providing stability and smoothness of movement during operation. Currently, there are many different variations of friction wedges made of different materials. For example, friction wedges are made of grey cast iron class 35 [Technical specifications 3183-234-01124323-2007], class 25 [Bondarenko A. F., Gorenkov A. A., Fedin V. M., Borts A. I., Hardening of friction wedge made of grey cast iron by volume-surface hardening II Vestnik VNIIZhT, 2010, volume 3, pp. 40-42.] as well as of 20 L grade steel [Gabets A. V., Developing the composition and technology for producing special modified cast iron with increased operational durability for friction units of railway rolling stock: PhD thesis in Technical Sciences: 05.16.01.—Moscow, 2014.], 20GL, 20FL, 20GTL grade steel [Bondarenko A. F., Gorenkov A. A., Fedin V. M., Borts A. I., Steel friction wedge hardened by volume-surface hardening II Vestnik VNIIZhT. 2010, volume 3, pp. 43-45. However, a general disadvantage of friction wedges made of said materials is insufficient hardness and wear resistance of the wedges for trucks with a load of over 25 tf per axle.
Therefore, it is the object of the present invention to provide an alternative structural material suitable for manufacturing friction shock absorbers of friction force vibrations, the material having increased strength and durability while being relatively inexpensive.
In the present invention, the aforementioned problem is solved by providing a new composition of alloyed cast steel characterized by the following content of elements (wt. %):
wherein the complex alloying coefficient CE for said steel calculated as CE=C+(Mn+Si)/6+(Cr+Mo+V)/5+(Ni+Cu)/15 is no less than 0.68% wt.
Thus, as a result of extensive research, the present inventors discovered that steel with the above narrowed ranges of carbon and manganese content, specified ranges of chromium, aluminium and vanadium content, and stricter requirements for phosphorus, sulfur, copper and nickel content, and characterized by the specified value of the calculated coefficient (i.e., the complex alloying coefficient CE) introduced by the inventors differs from the 30GSL grade steel selected as the prior art for the present invention in significantly higher hardness and wear resistance even without the use of advanced hardening methods. In particular, higher hardness and wear resistance values were achieved using conventional bulk hardening followed by tempering, and accordingly, the manufacturing cost increase for such steel is insignificant compared to prior art materials; in particular, said cost increase is 3-7% compared to that for 20GL grade steel, for example.
Thus, the technical effect of the invention is in providing increased hardness and wear resistance of articles made of the steel according to the invention without a significant increase in their manufacturing costs. Another technical effect is in providing increased hardness and wear resistance of surfaces of a friction wedge of freight car trucks and increased inter-repair service life of a friction wedge/friction plate friction pair. A further technical effect of the invention is in avoiding expensive processing methods for the disclosed steel and replacing them with simple bulk hardening followed by tempering, while providing an increase in hardness and wear resistance values.
The present invention further provides an article made of the steel according to the invention. According to a particular embodiment, the article is a friction wedge for freight car trucks.
CE=C+(Mn+Si)/6+(Cr+Mo+V)/5+(Ni+Cu)/15.
Comparative tests were carried out in order to determine hardness values for samples made of the steel according to the present invention as compared to the prior art materials used for manufacturing friction wedges: grey cast iron class 25 and steel grade 20GL. The test results are shown in Table 1 below.
Brinell hardness measurements for the samples were carried out in accordance with the following procedure.
GOST 9012-59: Metals. Brinell method for measuring hardness.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201891069 | May 2018 | EA | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/054484 | 5/30/2019 | WO | 00 |
