CN107312976A - A kind of bainite rail and production method - Google Patents

Abstract

The invention discloses a bainite steel rail and a production method thereof. The mass percentages of the chemical components of the raw material of the bainite steel rail are: C: 0.20-0.35%, Si: 0.8-1.2%, Mn: 1.8-2.2%, P≤ 0.035%, S≤0.035%, B: 0.001～0.003%, V: 0.06～0.08%, Ti: 0.02～0.05%, Cr: 0.1～0.3%, Cu≤0.02%, Mo＜0.005%, Als: 0.015～ 0.035%, Ca: 0.001-0.007%, and the balance is Fe and unavoidable impurity elements. The above ingredients go through a series of processes of molten iron desulfurization, converter smelting, argon station, LF refining, RH vacuum degassing, continuous casting, billet heating, rolling and post-rolling heat treatment to produce bainite with uniform structure and no segregation The steel rail has the advantages that: the surface of the bainitic steel rail produced by the method has no decarburized structure, low content of retained austenite, no martensite affecting performance, and less precious metal addition, which greatly reduces the production cost.

Description

A kind of bainite steel rail and its production method

technical field

The invention belongs to the production technical field of steel rails, in particular to a production method of bainitic steel rails.

Background technique

With the development of high-speed and heavy-duty railway trains, the service conditions of rails are becoming more and more harsh. Studies have shown that the main failure modes of rails are wear and contact fatigue. Rail rolling contact fatigue (RCF) is a common problem in the world's railway transportation, which not only affects the safety of railway transportation, but also shortens the service life of the rail and increases the maintenance cost of the line. In view of the fact that the traditional pearlitic rail steel cannot take into account the lack of anti-wear and anti-contact fatigue properties at the same time, the railway transportation departments of various countries have carried out a lot of research, mainly including research on damage mechanisms, research on new anti-contact fatigue rail materials and rail grinding. technology research. In terms of research on new rail materials, bainite steel is known as "the rail steel of the 21st century" for its excellent strength and toughness. After reasonable alloying and microstructure adjustment, the wear resistance and contact fatigue resistance of bainitic rail steel are better than the current pearlitic rail steel. In recent years, the damage of rails in my country has been significantly intensified after the railway speed is increased, and it appears in the form of new rolling contact fatigue damage such as tread oblique cracks and hidden damage. Therefore, it is necessary to carry out research on new rail materials while conducting research on rail grinding technology.

Patent CN201110040453.3 discloses a manufacturing method of non-quenched and tempered 1000MPa low-carbon bainitic high-strength steel plate. The process flow of the method is: KR molten iron pretreatment; converter smelting; sealed argon blowing alloy composition adjustment CAS treatment; Ladle furnace refining LF; vacuum degassing RH/VD; slab continuous casting; slab cutting and finishing; slab cold charging; slab reheating; double-stand controlled rolling; pre-straightening; ; Self-tempering in the insulation cover; air cooling to obtain finished steel plates. Its disadvantages are that the strength is too low to meet the requirements of the rail, and the process is complicated; the second is that precious metal Mo+Ni is added, and the cost is high.

Patent CN201110074144.8 discloses a low-carbon bainitic steel for engineering machinery, the chemical composition and weight percentage are: C: 0.05-0.10%, Si: 0.20-0.50%, Mn: 1.50-1.80%, S≤0.010 %, P≤0.018%, Nb≤0.10%, Mo≤0.10%, Ti: 0.010～0.040%, B: 0.0010～0.0030%, Cr: 0.20～0.50%, Al: 0.015～0.050%, the rest is Fe and trace Impurities. Using existing equipment, through molten iron pretreatment, double blowing converter smelting, LF refining, RH refining, slab continuous casting, through adjusting the content of some elements, microalloying treatment, TMCP process production, controlled rolling and water cooling, no heat treatment is required , to produce bainite construction machinery steel with high strength and good low temperature toughness. Its disadvantage is that the strength is too low to meet the requirements of the rail.

Contents of the invention

In order to overcome the defects of the prior art, the purpose of the present invention is to provide a production technology with simple process, low energy consumption and suitable for the existing industrial equipment level.

In order to achieve the above object, the present invention provides a kind of novel bainitic steel rail and production method thereof, as follows:

A bainite steel rail, the mass percent of the chemical composition of raw materials is: C: 0.20-0.35%, Si: 0.8-1.2%, Mn: 1.8-2.2%, P≤0.035%, S≤0.035%, B: 0.001～ 0.003%, V: 0.06～0.08%, Ti: 0.02～0.05%, Cr: 0.1～0.3%, Cu≤0.02%, Mo＜0.005%, Als: 0.015～0.035%, Ca: 0.001～0.007%, and the rest are Fe and unavoidable impurities.

A method for producing a bainite rail, the mass percentages of the chemical components of the raw materials used are: C: 0.20-0.35%, Si: 0.8-1.2%, Mn: 1.8-2.2%, P≤0.035%, S≤0.035% , B: 0.001～0.003%, V: 0.06～0.08%, Ti: 0.02～0.05%, Cr: 0.1～0.3%, Cu≤0.02%, Mo＜0.005%, Als: 0.015～0.035%, Ca: 0.001～ 0.007%, the rest is Fe and unavoidable impurities; in the continuous casting step of this production method, the tundish temperature is controlled at 15-25°C above the liquidus temperature, the casting speed is controlled at 0.3-0.5m/min, and the liquid core is used The reduction process forms the cast strand.

Specifically, the production method of the bainite rail also includes the steps of heating and rolling the billet. In the steps of heating the billet and rolling, the temperature of the slab heating zone II is 1050-1150°C, and the temperature of the cast slab heating zone I is 1200-1300°C. The hot section temperature is 1250-1300°C, the total heating time is 220-240min, the rolling start temperature is 1080-1180°C, and the final rolling temperature is 850-940°C.

Specifically, the production method of the bainitic steel rail also includes a post-rolling heat treatment step. In the post-rolling heat treatment step, the rolled piece passes through the track for 67 seconds with a wind pressure of 12-16 MPa, free air cooling after the upper cooling bed, and cooling in the lower cooling bed. Insulate in a heating furnace at 200-300°C for 1-1.5 hours, then air-cool to room temperature.

Specifically, the continuous casting is carried out with the liquid core pressing technology combined with electromagnetic stirring technology, the current intensity is 400-600A, the frequency is 5Hz, and the liquid core at the end is lightly pressed down by 8-10mm.

The invention utilizes Si to prevent the precipitation of carbides in the bainite phase transformation process, Mn to delay the high-temperature transformation of supercooled austenite, and a trace amount of boron to improve the hardenability of steel and promote the separation of pearlite and bainite transformation curves. Out of Mn-B bainite steel rail. Its beneficial effect is: 1) the structure of the bainitic steel rail produced by the method is uniform, without segregation, without decarburization structure on the surface, low content of retained austenite, and no martensite affecting performance; 2) low content of precious metals, The production cost is greatly reduced.

Description of drawings

Fig. 1 is the bainite microstructure diagram of the rail produced by this method

detailed description

The present invention will be further described below by way of examples, but the present invention is not limited. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the protection scope of the present invention.

Example 1:

1. A bainite steel rail, the mass percent of its raw material chemical composition is: C: 0.26%, Si: 0.8%, Mn: 1.93%, P: 0.013%, S: 0.008%, B: 0.0028%, V: 0.071%, Ti: 0.03%, Cr: 0.2%, Cu: 0.007%, Mo: 0.0007%, Als: 0.0286%, Ca: 0.004%, and the rest are Fe and impurity elements.

2. A production method of bainitic steel rail

Control the temperature of the upper continuous casting platform. During continuous casting, the temperature of the tundish is controlled at 23°C above the liquidus line, and the casting speed is controlled at 0.3m/min. The liquid core is pressed down and equipped with electromagnetic stirring technology to continuously cast a 280*380mm square Blank, the current intensity is 400A, the frequency is 5Hz; the liquid core at the end is lightly pressed down by 10mm.

Heating process parameters in billet heating and rolling steps: billet heating zone II temperature 1086°C, cast billet heating zone I temperature 1247°C, soaking section temperature: 1281°C, heating time 223min, overheating or overburning is not allowed, BD1 starts rolling Temperature: 1097°C, universal rolling finish temperature 863°C.

In the post-rolling heat treatment step, the rolled piece passes through a 100-meter-long fan pipeline at a speed of 1.5m/s, and the air pressure of the fan is 12MPa, and is freely air-cooled after being placed on a cooling bed. After lowering the cooling bed, keep it in a heating furnace at 300°C for 1 hour, and air-cool to room temperature.

Example 2:

1. A bainitic steel rail, the mass percent of the chemical composition of its raw materials is: C: 0.27%, Si: 1.17%, Mn: 1.82%, P: 0.018%, S: 0.011%, B: 0.0023%, V: 0.067%, Ti: 0.031%, Cr: 0.22%, Cu: 0.005%, Mo: 0.0005%, Als: 0.0223%, Ca: 0.006%, and the rest are Fe and impurity elements.

2. A production method of bainitic steel rail

Control the temperature of the upper continuous casting platform. During continuous casting, the temperature of the tundish is controlled at 21°C above the liquidus line, and the casting speed is controlled at 0.5m/min. The liquid core is pressed down and equipped with electromagnetic stirring technology to continuously cast a 280*380mm square Blank, current intensity 600A, frequency 5Hz; end liquid core lightly pressed down 8mm.

Heating process parameters in billet heating and rolling steps: billet heating zone II temperature 1105°C, cast billet heating zone I temperature 1278°C, soaking section temperature: 1291°C, heating time 233min, overheating or overburning is not allowed, BD1 starts rolling Temperature: 1174°C, universal rolling finish temperature 917°C.

In the post-rolling heat treatment step, the rolled piece passes through a 100-meter-long fan pipeline at a speed of 1.5m/s, and the air pressure of the fan is 14MPa, and is freely air-cooled after being placed on the cooling bed. After lowering the cooling bed, keep it in a heating furnace at 200°C for 1.5h, and air-cool to room temperature.

Example 3:

1. A bainitic steel rail, the mass percent of its raw material chemical composition is: C: 0.33%, Si: 1.1%, Mn: 2.08%, P: 0.015%, S: 0.012%, B: 0.0025%, V: 0.063%, Ti: 0.029%, Cr: 0.17%, Cu: 0.002%, Mo: 0.0002%, Als: 0.0272%, Ca: 0.007%, and the rest are Fe and impurity elements.

2. A production method of bainitic steel rail

Control the temperature of the upper continuous casting platform. During continuous casting, the temperature of the tundish is controlled at 18°C above the liquidus line, and the casting speed is controlled at 0.5m/min. The liquid core is pressed down and equipped with electromagnetic stirring technology to continuously cast a 280*380mm square Blank, the current intensity is 600A, the frequency is 5Hz; the liquid core at the end is lightly pressed down by 10mm.

Heating process parameters in billet heating and rolling steps: billet heating zone II temperature 1089°C, cast billet heating zone I temperature 1289°C, soaking section temperature: 1293°C, heating time 238min, overheating or overburning is not allowed, BD1 starts rolling Temperature: 1171°C, universal rolling finish temperature 938°C.

In the post-rolling heat treatment step, the rolled piece passes through a 100-meter-long fan pipeline at a speed of 1.5m/s, and the air pressure of the fan is 16MPa, and is freely air-cooled after being placed on the cooling bed. After lowering the cooling bed, keep it in a heating furnace at 270°C for 1.2h, and air-cool to room temperature.

Example 4:

1. A bainitic steel rail, the mass percent of its raw material chemical composition is: C: 0.20%, Si: 1.2%, Mn: 1.80%, P: 0.035%, S: 0.012%, B: 0.001%, V: 0.06%, Ti: 0.05%, Cr: 0.1%, Cu: 0.015%, Mo: 0.005%, Als: 0.015%, Ca: 0.003%, and the rest are Fe and impurity elements.

2. A production method of bainitic steel rail

Control the temperature of the upper continuous casting platform. During continuous casting, the temperature of the tundish is controlled at 15°C above the liquidus line, and the casting speed is controlled at 0.5m/min. The liquid core is pressed down and equipped with electromagnetic stirring technology to continuously cast a 280*380mm square Blank, the current intensity is 500A, the frequency is 5Hz; the liquid core at the end is lightly pressed down by 10mm.

Heating process parameters in the billet heating and rolling steps: billet heating zone II temperature 1050°C, cast billet heating zone I temperature 1200°C, soaking section temperature: 1250°C, heating time 240min, overheating or overburning is not allowed, BD1 starts rolling Temperature: 1080°C, universal rolling finish temperature 940°C.

In the post-rolling heat treatment step, the rolled piece passes through a 100-meter-long fan pipeline at a speed of 1.5m/s, and the air pressure of the fan is 13MPa, and is freely air-cooled after being placed on the cooling bed. After lowering the cooling bed, keep it in a heating furnace at 270°C for 1.5h, and air-cool to room temperature.

Example 5:

1. A bainite steel rail, the mass percent of its raw material chemical composition is: C: 0.35%, Si: 1.1%, Mn: 2.20%, P: 0.015%, S: 0.035%, B: 0.003%, V: 0.08%, Ti: 0.02%, Cr: 0.3%, Cu: 0.02%, Mo: 0.001%, Als: 0.035%, Ca: 0.001%, and the rest are Fe and impurity elements.

2. A production method of bainitic steel rail

Control the temperature of the upper continuous casting platform. During continuous casting, the temperature of the tundish is controlled at 25°C above the liquidus line, and the casting speed is controlled at 0.4m/min. The liquid core is pressed down and equipped with electromagnetic stirring technology to continuously cast a 280*380mm square Blank, current intensity 600A, frequency 5Hz; end liquid core lightly pressed down 9mm.

Heating process parameters in billet heating and rolling steps: billet heating zone II temperature 1150°C, cast billet heating zone I temperature 1300°C, soaking section temperature: 1300°C, heating time 220min, overheating or overburning is not allowed, BD1 starts rolling Temperature: 1180°C, universal rolling finish temperature 850°C.

In the post-rolling heat treatment step, the rolled piece passes through a 100-meter-long fan pipeline at a speed of 1.5m/s, and the air pressure of the fan is 15MPa, and is freely air-cooled after being placed on a cooling bed. After lowering the cooling bed, keep it in a heating furnace at 250°C for 1.2h, and air-cool to room temperature.

The bainite rails produced in Examples 1-5 were compared with two kinds of bainite rail products produced by a certain domestic factory, and the mass percentages of the chemical composition of the raw materials of comparative steel 1 were: C: 0.21%, Si: 1.41%, Mn : 2.10%, P: 0.009%, S: 0.01%, Cr: 0.57%, Mo: 0.35%, V: 0.005%; the mass percentages of the chemical components of the comparative steel 2 raw materials are: C: 0.23%, Si: 1.01%, Mn: 2.20%, P: 0.008%, S: 0.009%, Cr: 0.55%, Mo: 0.37%, V: 0.003%. The properties of the above five steels with different components were tested, and the results are shown in Table 1.

The performance comparison of the rail produced by each embodiment and comparative example of table 1

The schematic diagram of the microstructure of the accompanying drawing 1 shows an obvious bainite structure.

It can be seen from the table that the strength of the bainitic steel rail produced by the present invention is about 100Mpa higher than that of the steel grade of the comparative example, and it is better than the steel grade of the comparative example in terms of elongation and fracture toughness K _IC at -20°C , In addition, the content of participating austenite is also lower than that of the comparative steel.

Claims (5)

1. a kind of bainite rail, the mass percent of material chemical component is：C：0.20~0.35%, Si：0.8~1.2%, Mn：1.8~2.2%, P≤0.035%, S≤0.035%, B：0.001~0.003%, V：0.06~0.08%, Ti：0.02~ 0.05%th, Cr：0.1~0.3%, Cu≤0.02%, Mo ＜ 0.005%, Als：0.015~0.035%, Ca：0.001~ 0.007%, remaining is Fe and inevitable impurity.

2. a kind of production method of bainite rail, the mass percent of the material chemical component used for：C：0.20~ 0.35%th, Si：0.8~1.2%, Mn：1.8~2.2%, P≤0.035%, S≤0.035%, B：0.001~0.003%, V： 0.06~0.08%, Ti：0.02~0.05%, Cr：0.1~0.3%, Cu≤0.02%, Mo ＜ 0.005%, Als：0.015~ 0.035%th, Ca：0.001~0.007%, remaining is Fe and inevitable impurity；In the continuous casting step of the production method, in Bag temperature control is 15~25 DEG C more than liquidus temperature, and casting speed control is in 0.3~0.5m/min, using Liquid Core Reduction shape Into strand.

3. the production method of bainite rail according to claim 2, it is characterised in that：Also include heating steel billet and rolling In step, the heating steel billet and milling step, 1050~1150 DEG C of II area's temperature of heating strand, the area's temperature of heating strand I 1200~1300 DEG C, 1250~1300 DEG C of soaking zone temperature, total 220~240min of heat time, start rolling temperature 1080~1180 DEG C, 850~940 DEG C of finishing temperature.

4. the production method of bainite rail according to claim 2, it is characterised in that：Also include being heat-treated step after rolling Suddenly, it is described to roll in rear heat treatment step, rear rolled piece 67s is rolled by track, and blast is free air cooling after 12~16MPa, upper cold bed, 1~1.5h is incubated after lower cold bed in 200~300 DEG C of heating furnace, room temperature is air-cooled to.

5. the production method of bainite rail according to claim 2, it is characterised in that：The Liquid Core Reduction of use is matched somebody with somebody Continuous casting, 400~600A of current strength, frequency 5Hz, end 8~10mm of wick-containing slighter compress are carried out with electromagnetic agitating technology.