CN116397168A - Scratch-resistant high-strength and high-toughness steel rail and preparation method thereof - Google Patents

Abstract

A steel rail with scratch resistance and high strength and toughness comprises the following chemical components in parts by weight: and C:0.50-0.65%, si:0.45-0.95%, mn:0.35-0.85%, cr:0.30-0.80%, cu:0.20-0.55%, ni:0.10-0.30% and at least one of V, nb, ti, wherein V:0.02-0.15%, ti:0.001-0.030%, nb:0.01-0.08%, and the balance of Fe and unavoidable impurities. In addition, the invention also relates to a method for preparing the scratch-resistant and high-strength steel rail by utilizing the chemical components and the proportions. The invention solves the contradiction between the mechanical property and scratch resistance of the steel rail and realizes the good matching of the strength, toughness and scratch resistance of the steel rail.

Description

A scratch-resistant and high-strength steel rail and its preparation method

technical field

The invention relates to the technical field of rail manufacturing, in particular to a high-strength and tough rail with excellent scratch resistance and a preparation method thereof.

Background technique

Steel rail is one of the core components of rail transit wheel-rail system. With the construction of new rail transit projects and the ultimate pursuit of safety, comfort, efficiency and longevity in rail transit, the performance and quality of existing rails are facing new challenges. With the development of railway rails in the direction of longevity, the rails should not only have excellent wear resistance and fatigue resistance, but also have excellent abrasion resistance.

Rail abrasion is one of the main forms of rail damage in high-speed and heavy-duty railways at home and abroad, and it has been found in almost all major lines. Rail scratches seriously affect the smoothness of the track, and at the same time may cause the rail surface to peel off pieces, damage or fatigue cracks in the cross section. If not dealt with in time, it will increase the cost of rail repair and maintenance, and there is a risk of rail breakage. Rail scratches usually occur when the locomotive starts or brakes. Due to the abnormal sliding between the wheels and rails, a large amount of frictional heat is generated, and the surface of the rails usually forms a deep white layer. The abrasion process involves rapid heat exchange. The pearlite structure is first heated and transformed into austenite, followed by rapid cooling and then transformed into white martensite. The formation process of scratched white layer structure is essentially the process of quenching the base metal of rail to form martensite structure. Therefore, it can be generally judged from the martensite formation ability of rail steel and the ability to resist contact fatigue damage after the scratched white layer is formed on the surface of the rail. To evaluate the scratch resistance of rails. The greater the critical cooling rate of the rail steel, the better the scratch resistance of the rail; the higher the austenitization temperature of the rail steel, the less likely it is to form a scratch white layer during the friction process of the rail wheel and rail, and the thickness of the scratch white layer The thinner the rail, the better the scratch resistance of the rail; the same composition of the rail steel, the higher the hardness of the rail parent material, the smaller the hardness difference and gradient between the martensitic white layer and the parent material, and the higher the anti-stripping ability of the white layer. The stronger the fatigue fracture resistance of the rail is.

Patent document CN 112226697 A discloses a scratch-resistant steel rail and a production method thereof. This patent reduces the carbon content of the rail steel and uses long-term heating to make the depth of the decarburization layer of the rail greater than 0.5mm, further reducing the carbon content on the surface of the rail, thereby obtaining a high resistance to martensite formation. At the same time, High strength is maintained inside the rail. Although the method described in this patent improves the scratch resistance of the rail surface, the strength and hardness of the rail are reduced due to serious decarburization, and its anti-wear and contact fatigue performance will be greatly reduced, which will lead to surface peeling off block damage soon damage, reducing the service life of the rail. Simultaneously, this method only improves the anti-scratch ability of the very shallow surface layer of the rail, and after the surface layer is worn, the anti-scratch ability of the rail will decrease.

Therefore, in view of the above problems, it is desirable to provide a scratch-resistant and high-strength steel rail and a preparation method thereof.

Contents of the invention

Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is that the existing rail component design and production process cannot improve the strength and anti-scratch performance at the same time. Therefore, the present invention provides a scratch-resistant and high-strength steel rail and a preparation method thereof.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

According to one aspect of the present invention, a scratch-resistant and high-strength steel rail is provided, wherein the chemical composition and proportion of the steel rail are as follows: by mass percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn : 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, where V: 0.02-0.15%, Ti: 0.001- 0.030%, Nb: 0.01-0.08%, and the rest are Fe and unavoidable impurities.

In one embodiment of the present invention, in terms of mass percentage, the proportion of Si and Cr satisfies: 1.20%≤Si+Cr≤1.65%.

In one embodiment of the present invention, the ratio of Mn is 0.40-0.70% by mass percentage.

In one embodiment of the present invention, in terms of mass percentage, the ratio of Cu and Ni satisfies: 0.30%≤Cu+Ni≤0.50%.

According to another aspect of the present invention, there is also provided a method for preparing a scratch-resistant and high-strength steel rail, comprising the following steps:

1) Control the chemical composition and ratio of molten steel as follows: by weight percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20- 0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, of which V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities;

2) Place molten steel in a tundish for continuous casting, and use multi-stage electromagnetic stirring, low superheat and high casting speed to obtain low-segregation steel billets;

3) Place the steel billet in a walking heating furnace for heating, and then universally roll it into a steel rail;

4) Accelerated cooling with compressed air from the austenitic zone of the rail at an accelerated cooling rate of 5.0-6.5°C/s, cooling to 540-570°C and then cooling naturally.

In one embodiment of the present invention, in step 2), the low segregation billet is prepared from blast furnace molten iron through converter smelting, LF refining, electric heating and continuous casting; The segregation degree is 0.96-1.04, the Mn segregation degree is 0.97-1.03 and the Cr segregation degree is 0.97-1.03.

In one embodiment of the present invention, the continuous casting process of the low segregation steel slab adopts the multi-stage compound electromagnetic stirring of the mold electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring, the casting superheat is 12-20 ℃, and the cast slab casting speed is 0.82-0.95m/min.

In one embodiment of the present invention, in step 3), the heating process of billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950 ℃, and the heating time is 50-70min; The furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 70-100min; in the third stage, the furnace temperature of the heating furnace is 1200-1230°C, and the heating time is 50-90min; The time is not less than 90 minutes.

In one embodiment of the present invention, in step 3), universal rolling includes universal rough rolling, intermediate rolling and finish rolling.

In one embodiment of the present invention, in step 4), the accelerated cooling rate is 4.5-6.0°C/s, and the cooling is performed naturally after cooling to 430-470°C.

By adopting the above technical scheme, the present invention has the following advantages compared to the prior art:

The invention improves the austenitization temperature of the pearlite structure during the heating process through the specific composition design, improves the threshold for scratches, and reduces the thickness of the scratched white layer; Multi-stage compound electromagnetic stirring, low superheat casting and high casting speed process to obtain low segregation slabs, broaden the heat treatment window of rails, so that online heat treatment with high cooling speed can be implemented, and the synergy between alloying elements and heat treatment processes can be fully utilized to improve the performance of rails , obtain strong mechanical properties, and improve the anti-scratch performance, solve the contradiction between mechanical properties and anti-scratch properties, and achieve a good match between the strength, toughness and anti-scratch properties of the rail.

Detailed ways

It should be understood that the embodiments of the invention shown in the exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in the present invention, those skilled in the art will readily appreciate that many modifications are possible without materially departing from the teachings of the subject matter of the invention. Accordingly, all such modifications are intended to be included within the scope of this invention. Other substitutions, modifications, changes and deletions can be made to the designs, operating conditions and parameters of the following exemplary embodiments without departing from the gist of the present invention.

The invention provides a scratch-resistant and high-strength steel rail, wherein the chemical composition and proportion of the steel rail are as follows: by mass percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85% , Cr: 0.30-0.80%, Cu: 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, wherein V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities.

The invention improves the austenitization temperature of the pearlite structure in the heating process of the rail abrasion process through specific composition design, increases the threshold of abrasion occurrence, and reduces the thickness of the abrasion white layer.

In the above steel rails, in terms of mass percentage, the ratio of Si and Cr satisfies: 1.20%≤Si+Cr≤1.65%; the ratio of Mn is 0.40-0.70%; the ratio of Cu and Ni satisfies: 0.30%≤Cu +Ni≤0.50%.

In addition, the present invention also provides a method for preparing a scratch-resistant and high-strength steel rail, comprising the following steps:

1) Control the chemical composition and ratio of molten steel as follows: by weight percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20- 0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, of which V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities;

2) Place molten steel in a tundish for continuous casting, and use multi-stage electromagnetic stirring, low superheat and high casting speed to obtain low-segregation steel billets;

3) Place the steel billet in a walking heating furnace for heating, and then universally roll it into a steel rail;

4) Accelerated cooling with compressed air from the austenitic zone of the rail at an accelerated cooling rate of 5.0-6.5°C/s, cooling to 540-570°C and then cooling naturally.

The method of the present invention improves the austenitization temperature of the pearlite structure in the heating process in the rail scratch process through specific composition design, improves the threshold for scratching, and reduces the thickness of the scratched white layer; in the method of the present invention Cooperating with multi-stage composite electromagnetic stirring, low superheat casting and high casting speed to obtain low segregation billet, the window of rail heat treatment process is widened, so that high cooling speed online heat treatment can be implemented, and the synergy between alloy elements and heat treatment process can be fully utilized to improve the performance of rail It can obtain strong mechanical properties and improve scratch resistance, solve the contradiction between mechanical properties and scratch resistance, and achieve a good match between rail strength, toughness and scratch resistance.

In the above preparation method, in step 2), the low segregation steel slab is prepared from blast furnace molten iron through converter smelting, LF refining, electric heating and continuous casting; the C segregation degree in the narrow 50-150mm area of the low segregation billet is 0.96-1.04, Mn segregation degree is 0.97-1.03 and Cr segregation degree is 0.97-1.03.

In the above preparation method, the continuous casting process of the low segregation steel slab adopts the multi-stage composite electromagnetic stirring of the mold electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring, the casting superheat is 12-20 ℃, and the billet casting speed is 0.82-0.95 m/min.

In the above-mentioned preparation method, in step 3), the heating process of the billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, and the heating time is 50-70min; The temperature is 1100-1280°C, and the heating time is 70-100min; in the third stage, the furnace temperature of the heating furnace is 1200-1230°C, and the heating time is 50-90min; and the furnace temperature is more than 1200°C during the billet heating process. In 90min.

In the above preparation method, in step 3), universal rolling includes universal rough rolling, intermediate rolling and finish rolling.

In the above-mentioned preparation method, in step 4), preferably, the accelerated cooling rate is 4.5-6.0°C/s, cooled to 430-470°C and then cooled naturally.

The above technical solution of the present invention will be described in detail below through specific embodiments.

The main methods to improve the strength of rail steel include alloying, heat treatment, alloying + heat treatment, among which alloying + heat treatment is the most commonly used and effective method. For most of the alloying elements, the cooling C curve of the rail steel shifts to the right after its addition, and the critical cooling rate of martensite transformation will decrease, thereby improving the ability to form scratch white layer and reducing the scratch resistance. Under the existing composition system and production process, further improving the strength of the rail will inevitably reduce the anti-scuffing performance of the rail.

Therefore, in the present invention, through specific composition design, combined with the smelting and heating process, the segregation of the billet and the rail is reduced, the critical cooling rate of martensite transformation is greatly increased, and the process window of the heat treatment of the rail is widened, so that large cooling can be implemented. Fast online heat treatment, giving full play to the synergistic effect of alloy elements and heat treatment process to improve the performance of the rail; in addition, through the specific alloy composition design, the temperature of A1 and A3 of the rail is increased, and the anti-scratch performance of the rail is further improved. The invention improves the performance of the steel rail when the overall alloy content level is equal, or reduces the overall alloy content level under the condition of maintaining the existing performance, and improves the scratch resistance performance of the steel rail.

The invention provides a scratch-resistant and high-strength steel rail. The chemical composition of the rail matrix is composed of the following elements by weight percentage: C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, wherein, V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities.

Preferably, in the above-mentioned steel rail, the mass percentage content of Si and Cr satisfies the relationship: 1.20%≤Si+Cr≤1.65%, the mass percentage content of Mn: 0.40-0.70%, and the mass percentage content of Cu and Ni satisfies: 0.30%≤Cu+Ni ≤0.50% relationship.

The invention provides a scratch-resistant and high-strength steel rail, whose eutectoid transformation temperature A1: above 780°C, A3: above 810°C, the critical cooling rate of martensitic transformation > 6.0°C/s, and the wheel-rail scratch test Finally, the hardness ratio of scratched white layer/rail base metal is less than 1.80.

The present invention also provides a method for preparing a scratch-resistant and high-strength steel rail, the method comprising the following steps:

(1) Preparation of molten steel

Using blast furnace molten iron to smelt in converter, LF refining, and vacuum degassing to obtain molten steel with the following components: C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu : 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, where V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, and the rest are Fe and unavoidable impurities.

(2) Preparation of low segregation billet or billet

The molten steel with the above composition is placed in the tundish for continuous casting. The continuous casting process adopts multi-stage composite electromagnetic stirring of mold electromagnetic stirring, secondary cooling electromagnetic stirring and solidification end electromagnetic stirring. 0.82-0.95m/min. The low segregation degree cast slab is obtained through continuous casting, and the C segregation degree is 0.96-1.04, the Mn segregation degree is 0.97-1.03 and the Cr segregation degree is 0.97-1.03 in the area of 50-150mm narrow surface.

(3) Billet heating

The slab containing the above ingredients is placed in a walking heating furnace for heating. The heating process of the slab is divided into three stages: the first stage, the furnace temperature is 750-950°C, and the heating time is 50-70min; the second stage In the first stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 70-100min; in the third stage, the furnace temperature of the heating furnace is 1200-1230°C, and the heating time is 50-90min; The time at 1200°C is not less than 90min. Long-term high-temperature heating is to fully diffuse the segregated elements of the slab, improve the uniformity of the composition of the slab, and prevent the formation of point-shaped martensite structure due to the high cooling rate during the heat treatment process of subsequent accelerated cooling.

In order to prevent serious decarburization of the surface of the slab caused by long-term high-temperature heating, the surface of the slab is sprayed with high-temperature protective paint before loading into the furnace.

(4) Rail rolling

After the slab is heated, it is rolled into rails by billet rolling and universal rolling. The starting rolling temperature is 1150°C-1220°C, and the final rolling temperature is 880°C-930°C.

(5) On-line heat treatment after rolling

After the rail is rolled, the residual heat of rolling is used for reprocessing, and the temperature of the top surface of the rail is from 790°C to 820°C, and is cooled at a rate of 4.5-6.0°C/s to 430-470°C and then naturally cooled.

In the present invention, the steel slabs in the following examples and comparative examples are produced from molten iron in a blast furnace through converter smelting, LF refining, electric heating, and continuous casting by methods known to those skilled in the art.

Example 1

The chemical composition of the rail matrix in this example consists of the following elements by weight: C: 0.53%, Si: 0.63%, Mn: 0.68%, Cr: 0.76%, Cu: 0.30%, Ni: 0.17%, V: 0.09 %, the balance is Fe and other unavoidable impurities.

In this embodiment, the chemical composition of the billet and the rail matrix is consistent.

The molten steel containing the above components after blast furnace smelting, LF refining, and vacuum treatment is placed in the continuous casting tundish for continuous casting, and the multi-stage composite electromagnetic stirring of the crystallizer electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring is adopted. The casting superheat is 13-17°C, and the average casting speed of the slab is 0.86m/min. After cooling and cleaning, the billet is sprayed with anti-decarburization and then loaded into the walking heating furnace. In the first stage, the average temperature of the furnace chamber of the heating furnace is 836°C, and the heating time is 67 minutes; in the second stage, the average temperature of the furnace chamber of the heating furnace is 1250°C, the heating time is 86min; in the third stage, the furnace temperature is 1214°C, and the heating time is 81min. The cast slabs are turned into rails through billet rolling, universal initial rolling, universal intermediate rolling, and universal finish rolling. The temperature of the rails after rolling is 904°C. The center temperature of the top surface of the rail is 826°C and enters the rail on-line heat treatment unit for accelerated cooling at an average speed of 5.7°C/s to 447°C and then returns to the cooling bed to cool naturally to room temperature.

Example 2

The chemical composition of the rail matrix in this embodiment consists of the following elements by weight: C: 0.59%, Si: 0.78%, Mn: 0.57%, Cr: 0.52%, Cu: 0.24%, Ni: 0.15%, V: 0.07 %, the balance is Fe and other unavoidable impurities.

In this embodiment, the chemical composition of the billet and the rail matrix is consistent.

The molten steel containing the above components after blast furnace smelting, LF refining, and vacuum treatment is placed in the continuous casting tundish for continuous casting, and the multi-stage composite electromagnetic stirring of the crystallizer electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring is adopted. The casting superheat is 14-17°C, and the average casting speed of the slab is 0.85m/min. After cooling and cleaning, the billet is sprayed with anti-decarburization and then loaded into the walking heating furnace. In the first stage, the average temperature of the furnace hearth is 847°C, and the heating time is 71 minutes; in the second stage, the average temperature of the furnace hearth is 1243°C, the heating time is 91 minutes; in the third stage, the furnace temperature is 1207°C, and the heating time is 66 minutes. The cast slabs are turned into rails through billet rolling, universal preliminary rolling, universal intermediate rolling, and universal finishing rolling. The temperature of the rails after rolling is 893°C. The center temperature of the top surface of the rail is 821°C and enters the rail on-line heat treatment unit for accelerated cooling at an average speed of 5.3°C/s to 442°C and then returns to the cooling bed to cool naturally to room temperature.

Example 3

The chemical composition of the rail matrix in this example is composed of the following elements by weight: C: 0.63%, Si: 0.76%, Mn: 0.41%, Cr: 0.61%, Cu: 0.22%, Ni: 0.16%, V: 0.05 %, the balance is Fe and other unavoidable impurities.

In this embodiment, the chemical composition of the billet and the rail matrix is consistent.

The molten steel containing the above components after blast furnace smelting, LF refining, and vacuum treatment is placed in the continuous casting tundish for continuous casting, and the multi-stage composite electromagnetic stirring of the crystallizer electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring is adopted. The casting superheat is 15-18°C, and the average casting speed of the slab is 0.84m/min. After cooling and cleaning, the billet is sprayed with anti-decarburization and then loaded into the walking heating furnace. In the first stage, the average temperature of the furnace chamber of the heating furnace is 876°C, and the heating time is 61 minutes; in the second stage, the average temperature of the furnace chamber of the heating furnace is 1262°C, the heating time is 85min; in the third stage, the furnace temperature is 1224°C, and the heating time is 92min. The cast slabs are turned into rails through billet rolling, universal initial rolling, universal intermediate rolling, and universal finish rolling. The temperature of the rails after rolling is 907°C. The center temperature of the top surface of the rail is 817°C and enters the rail on-line heat treatment unit for accelerated cooling at an average speed of 5.0°C/s to 453°C and then returns to the cooling bed for natural cooling to room temperature.

Example 4

The chemical composition of the rail matrix in this embodiment is composed of the following elements by weight: C: 0.58%, Si: 0.95%, Mn: 0.58%, Cr: 0.43%, Cu: 0.21%, Ni: 0.16%, V: 0.08 %, the balance is Fe and other unavoidable impurities.

In this embodiment, the chemical composition of the billet and the rail matrix is consistent.

The molten steel containing the above components after blast furnace smelting, LF refining, and vacuum treatment is placed in the continuous casting tundish for continuous casting, and the multi-stage composite electromagnetic stirring of the crystallizer electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring is adopted. The casting superheat is 12-15°C, and the average casting speed of the slab is 0.86m/min. After cooling and cleaning, the billet is sprayed with anti-decarburization and then loaded into the walking heating furnace. In the first stage, the average temperature of the furnace hearth is 836°C, and the heating time is 65 minutes; in the second stage, the average temperature of the furnace hearth is 1256°C, the heating time is 89 minutes; in the third stage, the furnace temperature is 1215°C, and the heating time is 85 minutes. The cast slabs are turned into rails through billet rolling, universal initial rolling, universal intermediate rolling, and universal finish rolling. The temperature of the rails after rolling is 886°C. The center temperature of the top surface of the rail is 820°C and enters the rail on-line heat treatment unit for accelerated cooling at a rate of 5.5°C/s to 543°C and then returns to the cooling bed to cool naturally to room temperature.

Comparative example 1

The chemical composition of the rail matrix in Comparative Example 1 consists of the following elements by weight: C: 0.73%, Si: 0.35%, Mn: 1.13%, Cr: 0.12%, and the balance is Fe and other unavoidable impurities. Comparative Example 1 was prepared by an existing method. The superheat degree of continuous casting is 26-35℃, and the casting speed is 0.71m/min. Universal rolling method rolling, universal final rolling temperature 931 ℃. After rolling, use the residual heat of rolling to conduct online heat treatment, accelerate cooling to 548 °C at a rate of 2.1 °C/s, and then naturally cool to room temperature in air.

Comparative example 2

The chemical composition of the rail matrix in Comparative Example 2 consists of the following elements by weight: C: 0.77%, Si: 0.61%, Mn: 0.87%, Cr: 0.02%, V: 0.05%, the balance being Fe and other unavoidable of impurities. Comparative Example 1 was prepared by an existing method. The casting superheat degree of continuous casting is 28～36℃, and the casting speed is 0.71m/min. Universal rolling method rolling, universal final rolling temperature 927 ℃. After rolling, the waste heat of rolling was used for on-line heat treatment, accelerated cooling to 523 °C at a rate of 2.6 °C/s, and then naturally cooled to room temperature in air.

Comparative example 3

The chemical composition of the rail matrix in Comparative Example 3 consists of the following elements by weight: C: 0.59%, Si: 0.78%, Mn: 0.64%, Cr: 0.53%, Cu: 0.24%, Ni: 0.15%, V: 0.06 %, the balance is Fe and other unavoidable impurities. Comparative Example 3 was prepared by an existing method. The superheat degree of continuous casting is 27-35℃, and the casting speed is 0.71m/min. Universal rolling method rolling, universal final rolling temperature 926 ℃. After rolling, use the residual heat of rolling to conduct online heat treatment, accelerate cooling to 527 °C at a rate of 2.6 °C/s, and then naturally cool to room temperature in air.

Comparative example 4

The chemical composition of the rail matrix in Comparative Example 4 consists of the following elements by weight: C: 0.71%, Si: 0.36%, Mn: 1.04%, Cr: 0.09%, and the balance is Fe and other unavoidable impurities.

In this comparative example, the chemical composition of the billet and the rail matrix is consistent.

The molten steel containing the above components after blast furnace smelting, LF refining, and vacuum treatment is placed in the continuous casting tundish for continuous casting, and the multi-stage composite electromagnetic stirring of the crystallizer electromagnetic stirring, the secondary cooling electromagnetic stirring and the solidification end electromagnetic stirring is adopted. The casting superheat is 14-19°C, and the average casting speed of the slab is 0.84m/min. After cooling and cleaning, the billet is sprayed with anti-decarburization and then loaded into the walking heating furnace. In the first stage, the average temperature of the furnace hearth is 877°C, and the heating time is 65 minutes; in the second stage, the average temperature of the furnace hearth is 1250°C, the heating time is 76min; in the third stage, the furnace temperature is 1219°C, and the heating time is 88min. The cast slabs are turned into rails through billet rolling, universal preliminary rolling, universal intermediate rolling, and universal finishing rolling. The temperature of the rails after rolling is 902°C. The center temperature of the top surface of the rail is 811°C and enters the rail on-line heat treatment unit for accelerated cooling at a rate of 3.2°C/s to 463°C and then returns to the cooling bed to cool naturally to room temperature.

The steel rails prepared in Examples 1-4 and Comparative Examples 1-4 above were tested for yield strength, tensile strength and elongation according to GB/T 228.1 standard, and tested for Brinell hardness according to GB/T 231.1 standard. The contact fatigue life test is carried out on the TIME 8123 rolling contact fatigue testing machine, the test contact stress is 1200MPa, and the slip is 1.0%. The data of microstructure and conventional mechanical properties related to specific tests are shown in Table 1-2 below.

The microstructure and routine mechanical properties of table 1 embodiment and comparative example

It can be seen from the above Table 1 that the steel rail prepared by adopting the composition and process of the present invention has high strength and hardness, and at the same time maintains a high elongation after fracture. The critical cooling rate of tenite transformation reaches above 6.0°C/s. Comparative Example 1 is a U71Mn heat-treated steel rail produced by the current conventional process, and its strength, hardness and elongation after fracture are all lower than those prepared by the present invention. Speed 3.0°C/s. Comparative example 2 is the U75V heat-treated steel rail produced by the current conventional technology. Although its strength and hardness are slightly higher than the steel rail prepared by the present invention, its elongation after fracture is significantly lower than that of the steel rail prepared by the present invention. The A1 temperature is 726 ° C, and the A3 temperature 743°C, the critical cooling rate of martensitic transformation is 3.5°C/s. Comparative example 3 is a steel rail with the composition of the present invention but produced by a conventional process. Although the strength and hardness have been improved, the elongation after fracture is low, and the strength and toughness matching cannot be achieved. Comparative Example 4 is a steel rail produced by the process of the present invention with improved composition on the basis of U71Mn. The strength and plasticity are slightly improved compared with the U71Mn steel rail produced by the conventional process. The rapid cooling rate is 3.0°C/s. Therefore, the steel rail produced by this process has good strength and toughness, and the cooling rate of A1, A3 and martensitic critical transformation is greatly improved compared with conventional components and processes.

Table 2 Microstructure and conventional mechanical properties of Examples and Comparative Examples.

As can be seen from the above table 2, the steel rail prepared by the composition and process of the present invention has a high hardness of the rail parent material, but the hardness of the white layer formed by the abrasion is relatively low, so it has a low white layer/base metal hardness Ratio (below 1.80), that is, the hardness difference between the white layer and the base material, that is, the gradient is small, and at the same time, the scratched white layer is also thin, so it has a high rolling contact fatigue cycle. However, in Comparative Examples 1-4, whether it is the rail produced by the existing conventional composition and process or the steel rail produced by the optimized composition and conventional process or the steel rail with the existing composition and improved process, it cannot improve the toughness and abrasion resistance. Both damage and performance are taken into account at the same time.

It can be seen from the examples 1-4 and comparative examples 1-4 that the steel rail prepared by the present invention has good scratch resistance and good strength and toughness matching.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the implementation scope of the present invention; if it does not depart from the spirit and scope of the present invention, any modification or equivalent replacement of the present invention shall be covered by the claims of the present invention. within the scope of protection.

Claims (10)

1. A scratch-resistant and high-strength steel rail, characterized in that the chemical composition and proportion of the steel rail are as follows: by mass percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35 -0.85%, Cr: 0.30-0.80%, Cu: 0.20-0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, where V: 0.02-0.15%, Ti: 0.001-0.030% , Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities. 2. The scratch-resistant and high-strength steel rail according to claim 1, characterized in that, in terms of mass percentage, the proportion of Si and Cr satisfies: 1.20%≤Si+Cr≤1.65%. 3. The scratch-resistant and high-strength steel rail according to claim 1, characterized in that, in terms of mass percentage, the proportion of Mn is 0.40-0.70%. 4. The scratch-resistant and high-strength steel rail according to claim 1, characterized in that, in terms of mass percentage, the ratio of Cu and Ni satisfies: 0.30%≤Cu+Ni≤0.50%. 5. A method for preparing a scratch-resistant and high-strength steel rail, characterized in that it comprises the following steps: 1) Control the chemical composition and ratio of molten steel as follows: by weight percentage, C: 0.50-0.65%, Si: 0.45-0.95%, Mn: 0.35-0.85%, Cr: 0.30-0.80%, Cu: 0.20- 0.55%, Ni: 0.10-0.30%, and at least one of V, Nb, Ti, among which V: 0.02-0.15%, Ti: 0.001-0.030%, Nb: 0.01-0.08%, the rest is Fe and unavoidable impurities; 2) placing the molten steel in a tundish for continuous casting, and adopting a multi-stage electromagnetic stirring, low superheat and high casting speed process to obtain a steel billet with low segregation; 3) placing the steel billet in a walking heating furnace for heating, and rolling it into a steel rail through universal rolling; 4) Accelerated cooling with compressed air from the austenitic zone of the rail at an accelerated cooling rate of 5.0-6.5°C/s, cooling to 540-570°C and then cooling naturally. 6. The preparation method according to claim 5, characterized in that, in said step 2), said low-segregation billet is prepared from blast furnace molten iron through converter smelting, LF refining, electric heating and continuous casting; In the region of 50-150 mm narrow face of the low segregation slab, the C segregation degree is 0.96-1.04, the Mn segregation degree is 0.97-1.03 and the Cr segregation degree is 0.97-1.03. 7. preparation method according to claim 6, is characterized in that, the continuous casting process of described low segregation degree steel billet adopts the multistage composite electromagnetic stirring of crystallizer electromagnetic stirring, secondary cooling electromagnetic stirring and solidification terminal electromagnetic stirring, casting superheat degree 12-20°C, billet casting speed 0.82-0.95m/min. 8. The preparation method according to claim 5, characterized in that, in the step 3), the heating process of the billet is divided into three stages: in the first stage, the furnace temperature of the heating furnace is 750-950°C, The heating time is 50-70 minutes; in the second stage, the furnace temperature of the heating furnace is 1100-1280°C, and the heating time is 70-100min; in the third stage, the furnace temperature of the heating furnace is 1200-1230°C, and the heating time is 50-90min; and Controlling the time during which the furnace temperature is greater than 1200° C. during the billet heating process is not less than 90 minutes. 9. The preparation method according to claim 8, characterized in that, in the step 3), the universal rolling comprises universal rough rolling, intermediate rolling and finish rolling. 10. The preparation method according to claim 5, characterized in that, in the step 4), the accelerated cooling rate is 4.5-6.0°C/s, cooled to 430-470°C and then cooled naturally.