JPS6077962A - High-manganese austenitic steel - Google Patents

Abstract

PURPOSE:To prevent deterioration in the toughness of a high-Mn austenitic steel due to reduction in the cooling rate in a water toughening stage even in case of a large-sized or thick-walled member by adding a specified amount of Cr to the steel. CONSTITUTION:When a large-sized or thick-walled member requiring high yield strength and wear resistance is made of a high-Mn austenitic steel, a high-Mn steel contg. Cr and having a composition contg. 0.2-2.0% C, <0.8% Si, 5-30% Mn, 0.1-1.3% Cr, <0.07% P and <0.04% S is used. The member is subjected to heat treatment called water toughening by water cooling from 1,000-1,100 deg.C. At this time, the added Cr prevents deterioration in the toughness of the member due to reduction in the cooling rate caused by the large size or thick wall. Accordingly, a large-sized or thick-walled member with high toughness and wear resistance is easily obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a high manganese austenitic steel containing a large amount of manganese and having an austenitic structure at room temperature.

[Prior art]

Special steels made by adding special elements such as Cr + Mrly S 1 to carbon saws are rapidly cooled to exhibit an austenitic structure at room temperature, and such special steels are called austenitic steels. Among them, steels with a particularly high Mn content are called high manganese austenitic steels.

This type of high manganese austenitic steel has high yield strength and high abrasion resistance, so it is used in liners for rotary tables of crushers, rollers that crush materials between the liner, etc. due to its high yield strength and high wear resistance. It is widely used as a polishing material for parts that require high quality.

In order to increase its tenacity, this C-manganese austenitic steel is often subjected to a heat treatment called Mizukiri, in which it is cooled in water from a high temperature of 1000° to 1100°C. This produces a special steel that is hard only and has internal toughness. In addition, since conventional small items were drained at a cooling rate of IO8 to 104°C/min, they did not become brittle even without Cr.

However, in the case of large items that exceed 1 ton to be water-toughened, or in cases where the wall thickness is 150+ am or more even in parts, the cooling rate of water-toughening becomes slow, and the equilibrium state diagram shows that Since the steel cannot be cooled at a sufficiently fast cooling rate from the austenite single-phase temperature range, the toughness is significantly reduced and embrittlement occurs compared to a material of the same composition that has been cooled at a sufficiently fast cooling rate.

However, since high manganese austenitic steel has excellent properties such as toughness and wear resistance, there are many products that cannot be replaced with other steels. Attempts have been made to add elements such as MO.

However, Ni and MO are extremely expensive elements, and it is not effective unless the amount exceeds 3 to 5% by weight when adding Ni and 1 to 2N when adding Mo. There was a problem in that the cost of materials increased significantly.

[Summary of the invention]

In view of the above points, the present invention was made as a result of research on the embrittlement phenomenon during the cooling process by adding various elements to high manganese austenitic steels of various compositions. By adding a small amount of the element Cr, it is possible to prevent embrittlement during the cooling process, thereby providing a high manganese austenitic steel that is inexpensive and has excellent toughness and high wear resistance. Examples of the present invention will be described in detail below.

〔Example〕

The high manganese austenitic steel according to the present invention has a composition as shown in Table 1.

Table 1 First, the tensile strength of high manganese austenitic steel.

Elongation and wear ratio will be explained. Figures 1 to 3 show the test results of high manganese austenitic steel, with the horizontal axis representing the weight percent of C and the vertical axis representing the weight percent of Mll, respectively. Figure 1 shows the tensile strength, The second figure is elongated, the third figure is
The figures show the respective wear ratios. Furthermore, in each C<+, the dotted line (ill) indicates the range where the austenitic structure is formed, and the hatched range is the range where the tensile strength is 100 kg/lRJ or more in Fig.
In the figure, the elongation is in the range of 50% or more, and in Figure 3, the wear ratio is -
The range is 60% or less. .

As is clear from the figure, the best results are obtained when the weight percentage of C is 0.8 to 1.4 and the mold piece percentage of Mn is 10 to 16. However, the weight percent of C and Mn in the high manganese austenitic steel according to the present invention is determined by considering the range in which the austenitic structure shown in FIGS. In consideration of the fact that a high manganese steel called Super High Man has been developed, the content was limited to C062-2.0% and Mn 5-30%.

Next, C1,03,SiO,54,M,, 12.8
4. P O, 04, So, 007, with the same weight n1% other than Cr, and conventional products that do not contain Cr and C
Conventional one with r of 1.9 S view% (JIS SCMnH
ll) and C1• are 0.3% and 0.3%, respectively.
Table 2 shows the tensile strength and elongation test results comparing 5% eLO9'5 with the present invention.

Table 2: For each sample, the material was melted in a high-frequency melting furnace to a thickness of about 500 f, and the ingot was forged to 9 Mf, and after heat treatment, it was water-cooled to form an ausbunite single phase. After this, add the ingredients 5.
A test piece obtained by processing 5 simple φ x 451 + + + It was cooled from 1100°C at the cooling rate shown in the table in accordance with the actual cooling rate of thick material. It was processed into a No. Tl514A tensile test piece and tested.

As is clear from the table, the samples of the present invention are better in both tensile strength and elongation, and the difference in elongation is particularly remarkable. The effect of the present invention is obvious because the toughness of steel increases as the tensile strength and elongation increase. In particular, when the cooling rate is slow, that is, when the water-toughened article is large and thick-walled, the article of the present invention has less decrease in tensile strength and elongation than the article from 5e, and embrittlement is less likely to occur. Sai. Therefore, the thing of the present invention is t or thick j? It can be said to be a suitable material for meat products.

When Cr exceeds 1.5%, brittleness increases;
If Cr is less than 0.1% a/k, it becomes brittle and ineffective like conventional steels, so in the present invention, Cr is set at 0.1 to 1.3% in consideration of the actual scissor results.

In addition, other components and amounts such as St are determined according to JIS SCMnHl
I adopted it after meeting l. Furthermore, according to the experimental results, even if the amount of Cr was changed, the grain size was the same as that of the conventional one, and the wear resistance and narrow surface hardness were also the same as that of the conventional one. .

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, by adding a small amount of Cr, which is a low-cost source, to high manganese austenite resistance 1, the monthly profit in the cooling process of water toughness treatment is increased. embrittlement can be reduced,
A high-manganese austenitic steel with extremely good toughness and wear resistance can be obtained at low cost, and it has a remarkable effect in terms of resource conservation, and even if the cooling rate changes due to wall thickness or shape, the toughness does not decrease. The structural mechanical properties can be significantly improved.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing the test results of high manganese austenitic steel, with the horizontal axis representing the weight percent of C and the vertical axis representing the weight percent of KMn. Figure 1 shows the tensile strength. ,
Figure 2 shows good ranges for elongation and the third factor shows good ranges for wear ratio. Figure 1 Figure 3 C'/. Figure 2 C%

Claims (1)

[Claims] Each element is expressed as % by weight, CO12~2. ．． 0%, Jo, 8%
Below, Mn5-30 f's CrO, 1-1.3%
A high manganese austenitic steel characterized by having a content of , P O, 07% or less, S 2 O, 04% or less, and the remainder being Fe and unavoidable impurities.