RU2040580C1 - Steel - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: steel has the following components, wt.-% carbon 0.15-0.35; manganese 0.8-1.2; silicon 0.03-0.50; chrome 0.05-0.28; nickel 0.5-0.8; molybdenum 0.04-0.25; copper 0.01-0.30; aluminium 0.005-0.08; rare-earth metals 0-0.02; vanadium 0-0.15; alkaline-earth metals 0.001-0.02, and iron the rest at the following conditions: for providing required level of mechanical properties in normalized state the ratio must be: K $\genfrac{}{}{0ex}{}{\text{1}}{\text{0}}$ + K $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ x carbon + K $\genfrac{}{}{0ex}{}{\text{1}}{\text{2}}$ x nickel + K $\genfrac{}{}{0ex}{}{\text{1}}{\text{3}}$ x manganese creep limit is above 400 MPa where: K $\genfrac{}{}{0ex}{}{\text{1}}{\text{i}}$ multiple regression coefficient; for providing required level of mechanical properties after hardening and tempering the following ratio must be: K $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ x carbon + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ x manganese + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{3}}$ x chrome + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{4}}$ x silicon + K $\genfrac{}{}{0ex}{}{\text{2}}{\text{5}}$ · x t $\genfrac{}{}{0ex}{}{\text{°}}{\text{t}}$ creep limit is above 600 MPa where K $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ multiple regression coefficient; t $\genfrac{}{}{0ex}{}{\text{°}}{\text{t}}$ tempering temperature, C. EFFECT: improved mechanical properties at welding providing. 7 tbl

Description

 The invention relates to materials, in particular to foundry steels for the manufacture of critical parts of a trolley and coupler of freight railway cars.

Currently, these parts are made of steel grades 20GL, 20GFL, 30GSL according to GOST 22703-77 and TU 24.05.486-82. The yield strengths (σ _0.2 ) of these steels are not less than 314 MPa in the normalized state and 490 MPa after quenching and high tempering. The chemical composition and mechanical properties of foundry steel grades used in car building are shown in Table 1.

The increase in the carrying capacity of railway cars and their speed requires an increase in the bearing capacity and service life of the parts of the trolley and automatic coupler and, therefore, an increase in the structural strength of the casting steels used. According to the requirements of the Main Directorate of Carriage Management of the MPS for developed steels of increased strength, the yield strength σ _0.2 should be at least 400 MPa in the normalized state and at least 600 MPa after quenching and tempering without a significant decrease in ductility and cold resistance.

Work on the creation of high-strength steel is carried out by a number of organizations. One of these developments adopted for the prototype steel, containing, by weight. Carbon 0.10-0.30 Silicon 0.30-1.0 Manganese 0.30-1.60 Nickel 0.05-0.50 Chrome 0.10-0.50 Vanadium 0.04-0.15 Titanium 0 , 05-0.30 Aluminum 0.03-0.09 Alkaline earth metals (SHZM) 0.0005-0.06 Boron 0.0005-0.003 Copper 0.01-0.5 Nitrogen 0.05-0.5
However, this steel grade does not provide a specified level of mechanical properties and has a lower weldability due to the relatively high content of manganese and silicon.

The aim of the invention is to increase the mechanical properties of steel to a predetermined level both in normalized and thermally improved conditions while ensuring weldability at the level of serial steels. To meet the specified MPS requirements, we propose steel containing carbon, manganese, silicon, nickel, chromium, vanadium, copper, SCHM, aluminum additionally alloyed with molybdenum, and rare-earth metals (REM), with the following ratio of components, wt. Carbon 0.15-0.35 Manganese 0.80-1.20 Silicon 0.03-0.50 Chromium 0.05-0.28 Nickel 0.50-0.80 Molybdenum 0.04-0.25 Copper 0 , 01-0.30 Aluminum 0.005-0.08 REM 0.001-0.02 Vanadium 0.04-0.15 SCZM 0.001-0.02 Iron Else
The goal is achieved by the fact that in the proposed steel the nickel content is increased, molybdenum and REM are additionally introduced, the content of manganese and silicon is reduced. As impurities, the steel may contain up to 0.040 wt. sulfur and up to 0.040 wt. phosphorus.

 For steel intended for the manufacture of molded parts of a freight car, one of the most important characteristics is good weldability. Due to this circumstance, an increase in strength due to an increase in the content of carbon and manganese in steel is unacceptable, since these elements deteriorate weldability quite strongly. Without a noticeable deterioration in weldability, strength can be improved by alloying steel with nickel, molybdenum and vanadium. The minimum content of these elements is determined by their influence on the lower level of strength characteristics, and their maximum content by economic feasibility (high cost and scarcity). ShchZM and REM are introduced to increase the ductility, cold resistance of steel. The content of the remaining elements is determined by the steelmaking technology.

A feature of the proposed steel is a balanced and economical alloying with its main chemical elements. This is reflected in the mathematical modules obtained by analyzing the results of experiments on the composition of the property. According to these models, the ratios of the main alloying elements can only be selected according to certain rules. The positive effect of these models also lies in the fact that depending on the composition and type of heat treatment, the values of the mechanical characteristics of steel can be calculated (tensile strength and yield strength, elongation and contraction, impact strength). So, for example, one of the most important characteristics of the yield strength can be calculated by the following formulas:
in normalized condition
107 xC + 183 x Ni + 157 x Mn + + 195 σ _0.2
after quenching and tempering
XC + 325 209 112 hMn hCr 48 x xSi 0,378 xt + _TNA ^about 649 σ _0,2
where the numerical coefficients are multiple regression coefficients;
C, Ni, Mn, Cr, Si, respectively, the content of carbon, nickel, manganese, chromium, silicon in wt.

t ^o _ot tempering temperature, ^о С;
σ _0.2 yield strength, MPa.

 Separate results of calculations using these formulas are presented in Tables 3 and 7.

 Table 2.3 shows the chemical composition and properties of the known and proposed steel. It can be seen that the strength characteristics of 20GNO6L steel are much higher.

 In conditions when maximum plastic characteristics are not required from steel, alloying of steel with expensive and scarce rare-earth elements becomes impractical. Table 4.5 shows the chemical composition and properties of the known and proposed steel for this case. And in this case, the proposed steel 20GN06L has higher mechanical characteristics.

 It is possible to increase the plastic characteristics of steel due to a slight decrease in strength without giving vanadium to the steel.

 Table 6.7 shows the chemical composition and properties of 20GNO6L steel without vanadium. Steel 20GN06L has a significant advantage in properties in a normalized state.

 The use of 20GNO6L steel allows pouring out parts that pass both tempering and tempering from a single heat (one ladle), and parts that are subject to normalization only due to design features. This greatly simplifies and reduces the cost of the manufacturing process of parts, since instead of two grades of steel, only one can be used.

 In laboratory conditions, steel was smelted in induction furnaces, heat treated, and the mechanical properties of the proposed and known steel were studied. Metal casting was carried out in ingots weighing 15 kg, which were then subjected to heat treatment. Two industrial swimming trunks were carried out at the Lublin Foundry and Mechanical Plant.

 The optimal combination of chemical elements allows to obtain high strength properties with good ductility of the metal.

 An increase in the service life of cast parts by 1.3-1.5 times will allow saving on the operation of railway cars.

Claims (1)

 STEEL containing carbon, manganese, silicon, chromium, nickel, copper, aluminum, alkaline earth metals, vanadium, iron, characterized in that it additionally contains molybdenum and rare earth metals in the following ratio of components, wt. Carbon 0.15 0.35
Manganese 0.8 1.2
Silicon 0.03 0.5
Chrome 0.05 0.28
Nickel 0.5 0.8
Copper 0.01 0.3
Aluminum 0.005 0.08
Alkaline earth metals 0.001 0.02
Vanadium 0 0.15
Molybdenum 0.04 0.25
Rare earth metals 0 0.02
Iron Else
under the conditions:
to ensure a given level of mechanical properties in a normalized state, the relation

where k $\genfrac{}{}{0ex}{}{\text{1}}{\text{i}}$ multiple regression coefficient;
to ensure a given level of mechanical properties after quenching and tempering, the relation

where k $\genfrac{}{}{0ex}{}{\text{2}}{\text{i}}$ multiple regression coefficient
t _{o t p} tempering temperature, ^o C.

Images