JPS6017024B2 - Wear-resistant cast steel with improved internal hardenability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wear-resistant steel that has improved absolute hardness on the product surface as well as internal hardenability.

Generally, it is desirable to use wear-resistant mirror steel products, which have particularly high wear resistance, in addition to impact resistance and low cost, for parts of mining machines, civil engineering construction machines, and general industrial machines.

The specific value of the required mechanical properties is a tensile strength of 150k.
9/Iso or higher, hardness HB450 or higher, Charpy impact value 3
It is more than k9 one skin/c tiger. Additionally, the already known wear-resistant mirror steels have a basic composition of iron (Fe) and a large amount of compositions such as carbon (C), manganese (Mn), nickel (Ni), chromium (Cr), and molybdenum (Mo). However, these additive compositions are very expensive and have the drawback of significantly increasing the manufacturing cost of mirror steel products. The present invention aims to eliminate the above-mentioned drawbacks and provide a wear-resistant steel that can improve the surface and internal hardness of the product without impairing its impact resistance.

Hereinafter, the compositional elements of the twill steel of the present invention will be sequentially explained. Carbon (C) Carbon is an important element that affects hardness and impact value.

If it is less than 0.20%, the target hardness cannot be achieved. 0.35
% or more, the impact value is unsatisfactory.

Furthermore, the hardening effect of boron-added rust steel tends to decrease linearly as the carbon content increases, and in consideration of this, the carbon content was limited to 0.20% to 0.35%. Silicon (Si) Silicon is a deoxidizing element necessary for steel manufacturing, and is also an effective element for increasing the strength of the hard twill base and improving the resistance to temper softening.

If it is less than 1.00% or more than 1.30%, the hardness and impact value will decrease.

Manganese (MII) Like silicon, manganese is an effective element for deoxidation.

A content of 1.00% to 1.50% has the effect of improving hardenability and suppressing the impact deterioration effect of sulfur, but a content exceeding 1.50% results in a decrease in impact value.
Nickel (Ni) Nickel is an extremely effective element for increasing internal hardenability and improving impact value.

Addition of a large amount is not preferable because it increases cost. The content was set at 0.80% or more to obtain an internal hardening effect, and up to 1.50% to suppress manufacturing costs. Chromium (C
r) Chromium is an effective element for improving internal hardenability and resistance to temper softening.

However, like nickel, adding a large amount is not preferable because it increases cost. The content was set to 0.50% or more in order to obtain the effects of internal hardening property and temper softening resistance, and the content was set to 1.00% to suppress manufacturing costs. Titanium (Ti) Titanium has a denitrification effect to refine the microstructure and make the added boron effective. As shown in Table E below, when the Ti amount is 0.03% or less, the effectiveness of B is small; Moreover, when the Ti content is 0.10% or more, the ineffective B content increases and the effectiveness is lost.

Table E Boron (B) When boron is added in bulk, poron is added to the austenite and is adsorbed and concentrated at the grain boundaries at the quenching temperature above the AC3 point, stabilizing the austenite and improving the austenite property. It has an effect.

However, boron has a strong affinity with nitrogen, and therefore, if a certain amount of boron is added, ineffective precipitates (boron nitrides) will be formed, impairing the hardening effect, so the boron content should be reduced to 0. It was limited to 0.002% to 0.006%.

Regarding the hardness inside the product: C: 0.30%, Si: 1.0
5%, Mn: 1.31%, Ti: 0.05%, B: 0.
0033%, P: 0.015%, S: 0.013%, A
500 test pieces of Kagami steel (B-treated Senkei) with a composition of I: 0.10% and Fe: balance and Seneko (untreated Seneko) with no B added (composition and amount other than B are the same) (Both test pieces were tempered at 100oo) Results of a comparative test,
As shown in Figure 1, it was confirmed that boron is extremely effective in improving the hardenability inside the product.

Sulfur (S) and Phosphorus (P) Sulfur and phosphorus are unavoidable impurities and unnecessary elements contained in the steel bath during steel manufacturing.

Therefore, although it is desirable that there be no sulfur at all, based on current refining technology, sulfur is set at 0.015% or less, and phosphorus is set at 0.025% or less. Aluminum (N) Aluminum is a strong deoxidizing agent and has the effect of slightly improving the branability as shown in FIG.

The composition of the B-treated steel shown in Figure 2 is C: 0.30%;
Si: 1.05%, Mn: 1.31%, Ti: 0.05
%, B: 0.0033%, P: 0.015%, S: 0.
013%, N: 0.10%, Fe: balance, and the composition of untreated steel when only the AI content is 0.01, 0.04, 0.10, 0.20. So C:0.
30%, Si: 1.05%, Mn: 1.31%, Ti:
0.05%, P: 0.015%, S; 0.013%, A
I: 0.10%, Fe: the balance, only the rainbow content is 0
．． 01, 0.02, 0.04, 0.10, and 0.20.

Ordinary steel (aluminum content 0.03-0.04%)
Compared to
The content was set high at 8 to 0.12%, but if it exceeds 0.12%, the impact value decreases. Based on the above studies, the content range of each element was determined as follows based on the interaction with other elements.

C: 0.20-0.35
%Si: 1.00-1.3
0% Mm: 1.00~
1.50%Ni: 0.
80-1.50% Cr:
0.50-1.00% Ti:
0.03~0. Ship%B:
0.002-0.006%P:
0.025% or less S:
0.015% or less A:
○-08~0.12%Fe:
Table A below shows the composition of the steels used. Table A Then, the key steel products of the present invention having the above composition ratio are 850
After being held at a scorching temperature of ~900 qo, it was rapidly cooled and hardened, and then tempered at 100 ~ 300 qo and then subjected to material testing.

As is clear from Table B, Table B below shows the steel samples 1, 2,
The mechanical properties of case 3 are shown below.

As for the mechanical properties of the mirror steel of the present invention, the mechanical properties of the mirror steel of the present invention include tensile strength of 168 to 185K9, hardness of HB453 to 485, Charpy impact value of 3.0 to 4.0X9, and the target value of tensile strength of 150K9/ A hardness of pine or higher, a hardness of HB450 or higher, and a Charpy impact value of 3k9 per touch or higher were fully achieved.

In addition, Fig. 3 shows a wear-resistant single-branch steel that has been put into practical use in the past (refer to Tables C and D below for typical compositions and mechanical properties of single-brake wear-resistant steel) and a mirror of the present invention. The graph shows the difference in mechanical properties from steel (for composition and mechanical properties, see Tables A and B), and the figure shows that the steel of the present invention has the same strength and strength as general wear-resistant and rust-resistant steel. It is obvious that the impact resistance in terms of hardness is excellent. Table C Table D Figure 4 shows the degree of hardening from the tip to the base of tooth materials for power shovels made of the Zeni steel of the present invention and the Ichifune wear-resistant and rust-resistant steel, and it is clear from the figure. As can be seen, the cast steel of the present invention has significantly superior hardness both on the surface and inside.

Further, Fig. 5 and Table 1 below show the test results of comparing the degree of excavation wear when the excavation teeth made of the steel of the present invention and the cast steel of the present invention were attached to a power shovel bucket at the same time.

As shown in the figure and the table, the ratio of the amount of wear of the drill teeth made of the present invention to the amount of wear of the conventional teeth made of the steel is approximately 9.
It became 0%.

This practical test also confirmed the excellent wear resistance of the steel of the present invention. Table 1 further shows that the steel of the present invention is made of expensive chromium.
Since the compositions of nickel, manganese, and molybdenum are reduced or not required at all, the production cost can be significantly reduced compared to conventional steels in which large amounts of these components are added.

In addition, for conventional rust steel, the soaking temperature (Ac
Austenitization temperature of 3 or more points) from 950 to 1080
In contrast, in the case of the mirror steel of the present invention, it is as high as 85
Hardenability reaches its maximum value at a soaking temperature of 0 to 90,000.

Therefore, it has become possible to save energy by lowering the soaking temperature.

[Brief explanation of drawings]

Figure 1 is a graph showing the hardness distribution of B-treated key steel products and untreated rust steel products, and Figure 2 is a graph showing the relationship between aluminum content and hardening depth of B-treated steel and untreated steel. , 3rd
The figure shows the tensile strength of general wear-resistant rust-resistant steel and steel of the present invention.
A graph showing the relationship between hardness and impact value. Figure 4 is a graph comparing the internal hardening properties of general wear-resistant steel and steel of the present invention. Figure 5 is a graph showing conventional steel excavation in a power shovel field test. 1 is a graph showing the wear length of teeth and drilled teeth made of mirror steel according to the present invention. Figure 2 Figure 1 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 Carbon...0.20-0.35% Silicon...1.00~1.30% Manganese...1.00~1.50% Nickel...0.80~1.50% Chromium...0.50-1.00% Titanium...0.03~0.08% Boron...0.002~0.006% Phosphorus...0.025% or less Sulfur...0.015% or less Aluminum...0.08~0.12% Iron...the rest A wear-resistant cast steel with improved internal hardenability consisting of the above composition.