JPS59107066A - High-toughness and wear-resistant steel - Google Patents

Abstract

PURPOSE:To provide a titled steel which is inexpensive and has high resistance to softening by tempering at a high temp. by composing the same of C, Si, Mn, Cr, Mo, V, Ni and Fe, etc. and of a specific compsn. CONSTITUTION:A titled wear-resistant steel consists of 0.4-0.6mass% C, 1.6- 2.2% Si, <=0.5% Mn, 1-1.5% Cr, 0.8-1.2% Mo, 0.2-0.5% V, 1-2% Ni, and further 0.0005-0.001% B according to need and the balance Fe with ordinary impurities. Said steel is inexpensive, has excellent toughness and high resistance to softening by tempering and is suitable for a cutting edge, etc. of a motor grader. C and Si among the above-mentioned compsn. components is necessary to maintain wear resistance, toughness, etc., and Cr is necessary to maintain high hardness. Mo is effective in improving hardenability, toughness and resistance to softening by tempering, and V is effective in improving the resistance to softening by tempering and toughness as well as wear resistance. Ni improves thoughness and wear resistance. B contributes to an improvement in the resistance to softening by tempering, toughness and wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-toughness wear-resistant steel with high resistance to temper softening, which can be applied to cut-in edges of motor craters and the like.

Motor crater technology requires not only wear resistance, but also high toughness to withstand the various impacts received while the motor crater is in operation (generally, a glossy impact value of 8 kgmΔ or higher) is required. (2) A material with both abrasion resistance and high toughness is required.In addition, the cutting edge is tempered by the heat generated by friction with earth and sand during use, reducing its hardness. It has become clear that the abrasion resistance significantly decreases.In particular, Cuttic Enone, which is used for snow removal work from asphalt roads in snowy areas, generates a lot of heat due to friction with ice and asphalt, and the tip of Cuttic Edge is 500. ~60
Since it is exposed to high temperatures exceeding 0°C, there is a strong tendency for wear resistance to decrease, and there is a need for improved durability.

The material conventionally used for Motor Gray Ku Cutting Esso Shrine is JIS standard 5Or445.
Alternatively, there is the high 81 series W4 (Japanese Patent Publication No. 47-9901, etc.) which improves the tempering resistance of steel by increasing the Si content, and these are used for land leveling work where the temperature rise is relatively small or for small models. However, when used in conditions where the tip temperature exceeds 600℃, such as during snow removal work or with large models, it has the disadvantage of extremely low abrasion resistance. There is. In addition, there are some tool steels that have excellent wear resistance at high temperatures, but they not only have inferior toughness and workability, but also contain large amounts of expensive alloying elements, making them less resistant to wear compared to higher prices. It has the disadvantage that the rate of improvement in properties is small, making it unsuitable for use as a cut-in wedge, which should be inexpensive.

350-450 to obtain high hardness.
Even if the conventional Kutchin edge mill, which is tempered at ℃ and used, has a high initial hardness, it becomes soft after being operated once, and its wear resistance is significantly reduced.

The present invention was made in view of the above-mentioned facts and the drawbacks of conventional steels, and aims to provide a high-toughness, wear-resistant steel that is inexpensive and has excellent resistance to temper softening at high temperatures.

According to research conducted by the present inventors, steel in which fine carbides such as Or, Mo, V, and W are dispersed and precipitated has better temper softening resistance than steel in which coarse cementite is dispersed, even if the hardness at room temperature is low. It was found that the abrasion resistance was markedly improved. Therefore, the present invention has the following two points in order to utilize this knowledge.

(]) C0.4 to 0.6 in mass%. Si 1.6~2
．． 2. Mn 0.5 or less.

CrI~1.5. 84oO, 8-1.2. VO, 2~0
．． 5. A high-toughness wear-resistant steel with excellent resistance to temper softening at high temperatures, consisting of Nil~2, balance Fe, and normal impurities.

(2) CO in mass %, 4 to 0.6. Si 1.6~2
．． 2. MnO, 5 or less.

Or 1-1.5, ~Io O, 8-1.2, ~' 0
．． 2-0.5. NiI~2.

A high-toughness wear-resistant steel with excellent resistance to temper softening at high temperatures, consisting of 80.0005-0001 and the balance Fe and normal impurities.

Two reasons for limiting the numerical values of the present invention will be explained below.

C is a guideline for hardness and toughness to maintain wear resistance.To maintain hardness of 45 or higher, C is 04%.
It is necessary to contain the following.

However, if it exceeds 0.6%, Mo, which is a characteristic of the steel of the present invention,
This is also related to the interaction of V, but the carbides in the structure become coarser, increasing the hardness but decreasing the toughness value. At the same time, the shedding of lumpy carbides accelerates wear, which actually reduces the wear resistance. decrease. Therefore, C is 04-06%
limited to.

By coexisting with Ni, Si not only increases the hardness of the matrix, but also finely precipitates carbides during tempering, which is effective in improving toughness and wear resistance. If it is less than 16%, the effect is insufficient, while if it exceeds 22%, hardenability is inhibited.
It becomes necessary to increase the other 0r-Nifi, and at the same time, the toughness decreases and the susceptibility to quench cracking increases. Therefore, Si is limited to 1.6 to 22%.

Mn is an essential element used in normal steel manufacturing, but in the steel of the present invention, the amount is high, so if the Mn content is high, significant embrittlement will occur and toughness will decrease, so it is preferable to have as little as possible. Therefore, #n is limited to 0.05% or less as a range that does not cause any problems in normal steel manufacturing.

Or has the effect of improving hardenability, increasing hardness after hardening, and maintaining high hardness even after high-temperature tempering. In order to obtain such an effect, 1% or more of C is required due to the high 5ifil of the steel of the present invention, and even if it exceeds 15%, the hardenability is saturated.

Toughness decreases. Therefore, C[ is limited to 1 to 15%.

Mo enhances hardenability in relation to Or and N1, suppresses temper brittleness, and enhances toughness by dispersing cementite. Furthermore, in coexistence with ■, it stabilizes cementite and suppresses carbide aggregation during high temperature tempering.
(2) Since it promotes secondary hardening by carbides, it is an effective element for improving temper softening resistance, which is a feature of the present invention. Such an effect can be obtained with -F of 08% or more, but it is not synergized even if it exceeds 712%, and the effect is saturated and the toughness decreases. Therefore, Mo is limited to 0.8 to 12%.O2 produces fine carbides by tempering at high temperatures.
Secondary hardening of carbides results in increased resistance to temper softening, refinement of crystal grains, and increased toughness. (In order to prevent softening and maintain abrasion resistance, the
j.

The necessary power to coexist with Mo and bring out remarkable effects ≦ exists.

In order to obtain such an effect, 0.2% u,
- (2) is necessary, but by adding a large amount of V exceeding 0.6%, excessive precipitation of (2) carbides will coarsen the carbides and reduce wear resistance.

Therefore, ■ is limited to 02 to 05%.

Although N1 does not contribute to hardness improvement, it acts to prevent precipitates from leaving the base by increasing the toughness of the base, and as a result, improves the wear resistance of the steel.
Combined with the temper softening resistance of -F, it gives the steel excellent wear resistance.

This effect can be obtained with a content of 1% or more, but if it exceeds 2%, it will soften due to the precipitation of retained austenite.

Furthermore, since embrittlement occurs, it is necessary to increase the amount of expensive Mo in order to prevent embrittlement. Therefore, Ni is limited to 1 to 2%.

B contained in the second invention steel significantly increases the quenching hardness when added in a small amount. Furthermore, the tempering softening resistance at temperatures above 600° C. is high, and since the tempering temperature can be further increased, it is possible to improve the toughness and the wear resistance under the even more severe webbing 1. However, if the amount of addition is less than 0.10005%, the effective amount of holon will decrease due to oxidation and nitridation in the molten metal, so that sufficient effects cannot be obtained. Further, addition of a large amount exceeding 0,001% causes a boron compound to precipitate at one grain boundary, resulting in a decrease in toughness. Therefore, B is limited to 0.0005 to 0001%.

The present invention will be explained below with reference to Examples.

After melting, refining and ingot-forming steel with the alloy composition shown in Table 1, 150
It was hot rolled into a cross-sectional shape of mm width x 15 mm thickness. The heat treatment was diffusion annealing at 1025°C, standard temperature at 875°C, oil quenching at 925°C, and tempering at various temperatures. Furthermore, the conventional steel was subjected to a ratio test (normal temperature) and an abrasion test at a predetermined temperature for comparison.

The results are shown in Table 2.

In the abrasion test, a 15 mm x 150 mm test piece was tested using civil engineering concrete (compressive strength a 50 kg/c).
nl, coarse aggregate max. 20mm + slump i80mm)
7 Traveling speed, 8
．． The amount of wear after traveling 84 km at 4 km/hr was determined and compared. In addition, despite the high temperature of the test piece tip in this test, the hardness was high and the toughness was high.

It can be seen that both the wear resistance and the wear resistance are excellent.

Figure 2 compares the characteristics of the steel of the present invention with conventional steel using tempering performance curves.2 The temper softening resistance of the steel of the present invention is significantly large at temperatures of 400°C or higher, and the steel has sufficient hardness even when tempered at high temperatures. As a result, even if the tip of a cutting tip such as Quenon is exposed to a temperature close to 640°C, there is no decrease in hardness (it maintains its inherited wear resistance).

Figure 3 shows the high-temperature hardness curves of the steel of the present invention and the conventional steel.1 The steel of the present invention has a high tempering temperature.

Although the hardness at room temperature and O/low temperature range is lower than that of conventional steel.

There are few parishioners who become hard in the temperature range exceeding 400'C (.

It has less softening when exposed to high temperatures and is suitable for high γ products.
'? High hardness (and excellent wear resistance).

As stated above, the high-toughness wear-resistant steel of the present invention is inexpensive and has excellent toughness, and furthermore, it has high resistance to temper softening at high temperatures and has excellent wear resistance, so it can be used in general wear-resistant parts that require high toughness. It can be applied to various types of construction machinery, including cutting blades of full dosers, etc., and is especially suitable for cutting edges of motor craters.

Table 1 *B is the amount added, and all other than +1 are included! # (Analysis value) No.
2 Table 1 Bunch Button (Clothing and ℃ and As 771)

[Brief explanation of the drawing]

Figure 1 is a graph showing the maximum temperature quantification 15"I at the tip of cut ink during snow removal work in a motor crater, Figure 2 is a graph showing the tempering 1. It is a graph showing the hardness curves of steel and steel of the present invention. No. 17 Regular line speed (Km/Hr) Section 2 No. 3 (2)

Claims (1)

[Claims] (]) i amount% 00.4-0.6, S i 1
．． 6-2.2, Mn 0.5 or less. Cr I~1.5. Mo 0.8-1.2. V.O.
, 2-0, 5, a high-toughness wear-resistant steel with excellent resistance to temper softening at high temperatures, consisting of Ni I-2 and the remainder Fe and normal impurities. (2) Mass%: 00.4 to 0.6. Si 1.6~2
．． 2. h4n O, 5 or less. Or 1-1.5, Mo 0.8-1.2. V
0.2-0.5. Ni+-2, HO, 0005~0
．． High toughness and wear resistance tg4 with excellent resistance to temper softening at high temperatures, consisting of 001 and impurities of Fe and 0'1JfJii.
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