JP2000129397A - Pearlite type rail excellent in wear resistance and ductility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the wear resistance and ductility of a rail in such a manner that breaking does not occur by the change of atmospheric temp. and the temp. change when welding by preparing a rail contg. a specified compsn. of elements. SOLUTION: A pearlite type rail preferably contg., by weight, 0.75 to 0.84% C, 0.10 to 1% Si, 0.40 to 2.5% Mn, <=0.035% P, <=0.035% S and 0.05 to 0.5% V is prepd. In this way, a rail used in a severe environment such as a high axle load railload heavy in railload weight and having many sharp curve parts is obtd. Moreover, in the case one or >= two kinds of elements selected from 0.05 to 1.5% Cr, 0.1 to 1% Cu, 0.1 to 1% Ni and 0.1 to 2% Mo are incorporated in addition to the componential system, by solid solution strengthening, it can be hardened, and its wear resistance can moreover be improved. Furthermore, in the case 0.0005 to 0.15% Nb is incorporated, it is bonded with C in the steel after rolling to form fine carbides, so that its wear resistance can moreover be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heavy wagon,
Also, the present invention relates to a pearlite-type rail having excellent wear resistance and ductility used in a severe environment such as a high axle heavy railway having many sharp curves.

[0002]

2. Description of the Related Art Currently, pearlite-type heat-treated rails with a C content of about 0.7% by weight with an emphasis on wear resistance in order to extend the life of rails used in high axle heavy railways that mainly transport ore. Is used.

Recently, JP-A-8-109439 and JP-A-8-14
No. 4016 discloses that the amount of C is increased to a range of 0.85 to 1.2% by weight to increase the fraction of cementite, and
No. 6100 and JP-A-8-246101, the C content is 0.85 to
A method has been proposed in which the abrasion resistance is further improved by increasing the content to a range of 1.2% by weight and further heat-treating the rail head to increase the hardness.

[0004]

However, in the method disclosed in the above-mentioned patent gazette, since the C content is contained at 0.85% by weight or more, ductility is remarkably reduced, and the temperature difference occurs in summer and winter. Breakage of the rail is likely to occur due to thermal expansion and contraction, and large expansion and contraction at the time of welding that occurs when manufacturing a long rail (200 to 1500 m) whose usage has been increasing in recent years.

The present invention has been made to solve such a problem, and has excellent abrasion resistance. In addition, the present invention provides abrasion resistance and ductility that do not break due to a change in temperature or a temperature during welding. An object is to provide an excellent perlite type rail.

[0006]

Means for Solving the Problems The above problems are expressed in terms of% by weight,
C: 0.75 to 0.84%, Si: 0.10 to 1%, Mn: 0.40 to 2.5%, P:
The problem is solved by a pearlitic rail having excellent wear resistance and ductility containing 0.035% or less, S: 0.035% or less, and V: 0.05 to 0.5%.

The reasons for limiting the components will be described below.

C: An important element for the present invention together with V described later. In general, it is already known that the wear resistance is improved and the ductility is reduced with an increase in the amount of C. However, the ductility that does not break due to the comparison of the wear resistance with the current heat treated rail and the expansion and contraction during welding is already known. The relationship with is unknown.

Therefore, the content of components other than the C content is within the scope of the present invention, and a pearlite-type rail was manufactured using steel having a different C content, and the wear resistance and ductility were investigated.

[0010] Here, the wear resistance is measured from the rail head to the diameter.
A 30 mm Nishihara type abrasion test piece was sampled, and using a Nishihara type abrasion tester, a contact pressure of 1.4 GPa, a slip ratio of -10%, and a drying condition of 10% were used.
Evaluated by the amount of wear after 10,000 rotations, if the wear amount is reduced by 3% or more compared to the current pearlite type heat treated rail,
It was judged that there was an effect. The ductility of the ASTM round bar specimen
(Parallel part 9mmφ, gauge part 36mm) tensile test elongation
(El) was evaluated. AREA (American Railway Engi
neering Association, 1992) Chapter4.The standard described in Rail stipulates that this El is required to be 10% or more. Can be prevented.

FIG. 1 shows the relationship between the C amount, the wear amount, and El. If the C content is 0.75% by weight or more, the wear amount is reduced by 3% or more compared to the current pearlitic heat treatment rail, and if it is 0.84% by weight or less, El of 10% or more can be obtained. Understand. Therefore, the amount of C is limited to 0.75 to 0.84% by weight.

Si: Not only is it effective as a deoxidizing agent,
Solid solution increases strength and improves wear resistance.
If it is less than 10% by weight, no curing is observed. 1% by weight
If it exceeds, the effect is saturated and the weldability deteriorates. Therefore, the amount of Si is limited to 0.10 to 1% by weight.

Mn: Since the transformation temperature is lowered, the lamella spacing of the pearlite structure can be reduced, and the rail can be made stronger.
It is an element effective for increasing toughness. If it is less than 0.40% by weight, the effect is small, and if it exceeds 2.5% by weight, microsegregation is increased and a martensitic structure is easily generated, and ductility is remarkably reduced at the time of heat treatment or welding, and the material becomes brittle. Therefore, the amount of Mn is limited to 0.40 to 2.5% by weight.

P: If it exceeds 0.035% by weight, toughness deteriorates. Therefore, the P content is limited to 0.035% by weight or less.

S: If it exceeds 0.035% by weight, sulfide-based inclusions increase remarkably and become brittle. Therefore, the amount of S is limited to 0.035% by weight or less.

V: As described above, together with C, V is an important element for the present invention. After rolling, it forms fine carbides by combining with C in the steel, and hardens to the inside of the rail head by precipitation hardening, greatly improving wear resistance. Further, the pearlite colony is also finely divided by the finely dispersed carbide, which contributes to improvement of ductility.

Therefore, the content of components other than the V content is within the scope of the present invention, and a pearlite-type rail is manufactured using steel of which the V content is changed, and El is measured by the above-described method to determine the optimum V content. The range was investigated.

FIG. 2 shows the relationship between the amount of V and El. V amount to 0.0
It is understood that when the content is 5% by weight or more, El of 10% or more can be obtained. However, if the content exceeds 0.5% by weight, the weldability deteriorates.
Therefore, the amount of V is limited to 0.05 to 0.5% by weight.

Further, as is apparent from FIG.
If V exceeds V, the effect of improving ductility saturates. Therefore, it is preferable to set the V content to 0.05 to 0.2% by weight from an economic viewpoint.

A slab of the above-mentioned component system is prepared and, for example, 12
If heated to 00 ° C or higher, hot-rolled to a rail at 900 ° C or higher, and cooled at a cooling rate of 3 ° C / sec or less to form a pearlite structure, the pearlite of the present invention having excellent wear resistance and ductility is obtained. Mold rails can be manufactured.

In addition to the above components, Cr: 0.05 to
If one or more elements selected from 1.5%, Cu: 0.1-1%, Ni: 0.1-1%, Mo: 0.1-2% are included, it can be hardened by solid solution strengthening. And abrasion resistance can be further improved.

The upper limit of each element is based on the following reasons. Cr content
If it exceeds 1.5% by weight, the weldability will deteriorate. Cu content is 1% by weight
If it exceeds, Cu cracks occur. If the amount of Ni exceeds 1% by weight, the effect of Ni is saturated, leading to an increase in cost. In addition,
Ni is effective not only for solid solution strengthening but also for improving toughness and preventing Cu cracking. If the amount of Mo exceeds 2% by weight, the effect of Mo is saturated, leading to an increase in cost. In addition, if the content of Nb: 0.005 to 0.15% by weight in addition to the above component system is included, after rolling, it is combined with C in the steel to form a fine carbide and is hardened to the inside of the rail head by precipitation hardening. Therefore, the wear resistance can be further improved. If the amount of Nb exceeds 0.15% by weight, the effect of Nb is saturated, leading to an increase in cost.

[0023]

EXAMPLES (Example 1) A steel having the composition shown in Table 1 was melted and made into a bloom, heated to 1250 ° C, and rolled at 920 ° C.
By cooling at a cooling rate of 33 ° C./sec, samples 1 to 26 of pearlite type rails were produced.

Then, the abrasion resistance was measured by the Nishihara-type abrasion test and the El was measured by the tensile test, and the abrasion resistance and ductility were evaluated as described above. In addition, Vickers hardness (load 10 kgf) was measured at a depth of 5 mm from the rail head. According to the above-mentioned AREA standard, Vickers hardness is 340 to 399.
Must be within the range.

The results are shown in Table 1. Samples 4, 5, 6, 7, 12, 15, 16, 17, and 20 having the components of the present invention show a reduction in wear of 3% or more compared to the current pearlite-type heat-treated rail, and more than 10% El is obtained, and it can be said that it is a pearlite type rail excellent in both abrasion resistance and ductility. Also,
In these samples, the Vickers hardness is also within the range of the AREA standard.

On the other hand, Sample 1 having a C content lower than the range of the present invention,
2, 3, 21, 22, 23, 24, and the amount of Si, the amount of Mn, and the amounts of Si and Mn of Samples 11, 13, and 14 lower than the range of the present invention, the amount of wear was 3% compared to the current pearlite-type heat-treated rail. The above reduction is not observed, and excellent wear resistance cannot be obtained. In samples 8, 9, 10, 18, 19, and 25 in which the C content was higher than the range of the present invention, excellent wear resistance was obtained.However, since eutectoid cementite was formed, El of 10% or more was obtained. I can't.

[0027]

【table 1】

(Example 2) Steel having the components shown in Table 2 with mainly different amounts of V was melted and made into a bloom, and heated to 1280 ° C to produce
After finishing the rolling at 0 ° C., the sample was cooled at a cooling rate of 0.5 to 3 ° C./sec to prepare samples 26 to 36 of pearlite-type rails, and
The same test was performed.

The results are shown in Table 2. For all samples, the wear amount was 3% compared to the current pearlitic heat treated rail.
The above reduction is recognized, and excellent wear resistance is obtained,
In Samples 26 and 27 in which the V content is lower than the range of the present invention, El of 10% or more
Can not be obtained.

[0030]

[Table 2]

[0031]

Since the present invention is constructed as described above, it has excellent abrasion resistance, and also has excellent abrasion resistance and ductility which do not cause breakage due to changes in air temperature or temperature during welding. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a C amount, a wear amount, and El.

FIG. 2 is a diagram showing a relationship between a V amount and El.

Claims (4)

[Claims] 1. C .: 0.75 to 0.84% by weight, Si: 0.10 to 1% by weight
%, Mn: 0.40 to 2.5%, P: 0.035% or less, S: 0.035% or less,
V: A pearlitic rail containing 0.05 to 0.5% and having excellent wear resistance and ductility. 2. The pearlite-type rail according to claim 1, wherein the content of V is 0.05 to 0.2%. 3. The weight percentage of Cr: 0.05-1.5%, Cu: 0.1-1.
%, Ni: 0.1 to 1%, Mo: 0.1 to 2%, containing one or more elements selected from the group consisting of excellent wear resistance and ductility according to claim 1 or claim 2. Perlite type rail. 4. The pearlitic rail according to claim 1, which contains 0.005 to 0.15% by weight of Nb in terms of% by weight.