KR102063134B1 - High Chrome Cast Iron With Excellent Abrasion Resistance and Corrosion Resistance - Google Patents

Abstract

The present invention relates to high chromium cast iron having excellent abrasion resistance and corrosion resistance, C: 1-3 wt%, Si: 2 wt% or less, Mn: 2 wt% or less, Cr: 25-27 wt%, Mo: 0.4-1 wt%, V: 1% or less, Ni: 4-6wt%, Ti: 1wt% or less, Nb: 1wt% or less, and the balance is characterized by including an alloy composition of Fe and other unavoidable impurities, thereby ensuring excellent castability and wear resistance In addition, it can secure excellent corrosion resistance and can be used for a long time even in the field where strong acid and base are discharged, which can extend the replacement cycle of parts and reduce the replacement cost.

Description

High Chrome Cast Iron With Excellent Abrasion Resistance and Corrosion Resistance}

The present invention relates to high chromium cast iron having excellent abrasion resistance and corrosion resistance, and in particular, to a high chromium cast iron having excellent wear resistance and corrosion resistance that does not cause damage or corrosion even after long-term contact with a strong acid or strong base.

In general, the mechanical components that make up the mechanism for transporting materials characterized by strong acids or bases should be made of materials that are highly wear and corrosion resistant.

In particular, the long-term exposure of the mechanical parts during the transfer of suspensions made of strong acids or bases may cause corrosion and damage, resulting in a breakdown resulting in a significant drop in product productivity.

Of course, stainless steel with excellent corrosion resistance may be adopted, but if it is in contact with a strong acid or strong base for a long time, it may cause corrosion and breakage. In particular, when applied to a rotating part or a friction part, it is checked by an increase in crack generation. There is a problem that the cycle is shortened and the productivity is greatly lowered.

1. Korean Registered Patent Publication No. 10-1020174 (2011.02.28) "Austenitic Spheroidal Graphite Cast Iron with Excellent Corrosion Resistance"

The present invention has been made to solve the above-mentioned problems of the prior art, an object of the present invention is a high chromium excellent in wear resistance and corrosion resistance that does not cause damage, such as corrosion or cracking even long-term contact with a material made of a strong acid or base To provide cast iron.

In order to achieve the above object, high chrome cast iron excellent in wear resistance and corrosion resistance according to the present invention,

C: 1.0-3.0 wt%, Si: 2.0 wt% or less, Mn: 2.0 wt% or less, Cr: 25.0-27.0 wt%, Mo: 0.4-1.0 wt%, V: 1.0% or less, Ni: 4.0-6.0 wt% %, Ti: 1.0 wt% or less, Nb: 1.0 wt% or less, and the balance is characterized by including an alloy composition of Fe and other unavoidable impurities.

In addition, high chromium cast iron excellent in wear resistance and corrosion resistance according to the invention is characterized in that the hardness HRC 50 ~ 60, tensile strength 500 ~ 700MPa.

According to the present invention having the configuration as described above, through the Ni content of 4.0 ~ 6.0wt% to ensure excellent castability, corrosion resistance and wear resistance, and further comprising a titanium, vanadium, and niobium component to maintain the wear resistance At the same time, it has excellent corrosion resistance and can be used for a long time even in the field where strong acid and base are discharged, thereby extending the replacement cycle of components and reducing the replacement cost.

1 is an enlarged photograph of a specimen cross section of high chromium cast iron according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. The following examples are only intended to illustrate the invention and do not limit the scope of the invention.

The high chromium cast iron according to the present invention uses high chromium steel with high chromium content to secure excellent wear resistance, and further includes molybdenum, nickel, vanadium, titanium, and niobium, which is characterized by securing excellent corrosion resistance with wear resistance.

Specifically, the basic composition of the high chromium cast iron having excellent wear resistance and corrosion resistance of the present invention is C: 1.0 to 3.0 wt%, Si: 2.0 wt% or less, Mn: 2.0 wt% or less, Cr: 25.0 to 27.0 wt%, and Mo: 0.4-1.0 wt%, V: 1.0% or less, Ni: 4.0-6.0 wt%, Ti: 1.0 wt% or less, Nb: 1.0 wt% or less, and the balance includes an alloy composition of Fe and other unavoidable impurities.

As shown in FIG. 1, when the cross section of the specimen according to the present invention is photographed at a magnification of 100 times, primary austenite (black dots) appears, and the austenite phase transformation into martensite contributes to improving wear resistance and remains Austenitic contributes to improved corrosion resistance.

In particular, by including the Ni: 4.0 ~ 6.0wt%, Ti: 1.0wt% or less, and Nb: 1.0wt% to increase the corrosion resistance and wear resistance of cast iron.

In addition, the HRC hardness of the high chrome cast iron according to the present invention is 50 ~ 60, the tensile strength is 500 ~ 700MPa.

Hereinafter, the critical meaning of the composition of the high chromium cast iron according to the present invention will be described.

(1) C: 1.0-3.0wt%

Carbon contributes to stabilizing austenite and to the shape of strength.

In addition, carbon combines with chromium and molybdenum to form carbonides, thereby improving the strength and hardness and inhibiting the formation of delta ferrite, which causes brittleness.

As the carbon content increases, the hardness value increases, but when the content exceeds 3.0wt%, brittleness increases, and when the content is less than 1.0wt%, the wear resistance decreases, and the parts may be easily worn by strong acid.

(2) Si: 2.0 wt% or less

Silicon is contained as a deoxidizer to remove oxygen in steel and improves quenchability and fatigue strength.

However, when silicon exceeds 2.0wt%, the toughness is lowered and the surface defect may occur during heat treatment, so it is limited to 2.0wt% or less.

(3) Mn: 2.0 wt% or less

Manganese gains strength through strengthening employment and improving hardenability.

However, when the content of manganese exceeds 2.0wt%, segregation may increase sharply, brittleness may increase, and hardening cracks or deformation may be caused.

(4) Cr: 25.0 ~ 27.0wt%

In this embodiment, chromium is included to improve wear resistance and hardness.

Chromium combines with carbon to form carbides to prevent carbon diffusion, improving wear resistance and corrosion resistance, and preventing coarsening of crystal grains to improve hardness.

If chromium is contained in an amount exceeding 27.0 wt%, the tissue grows in a needle shape due to excessive reaction with carbon, resulting in a decrease in impact resistance. If the content is less than 25.0 wt%, the impact resistance is good but the wear resistance is weakened. In the manufacture of parts, there is a fear of being easily worn by strong acidic or basic materials.

Next, the critical significance of the composition of the material added to ensure corrosion resistance is explained.

(5) Mo: 0.4 ~ 1.0wt%

Molybdenum is a substitutional element that enhances the strength of steel by solid solution strengthening effect.

In the present invention, molybdenum is added to improve the hardenability of the steel and to improve corrosion resistance and toughness.

Molybdenum is an excellent corrosion resistance element, and when used in combination with chromium rather than using molybdenum alone, it is more effective in improving hardenability.

Molybdenum also serves to prevent tempering brittleness in subsequent heat treatments.

If the molybdenum is less than 0.4 wt%, the corrosion resistance and toughness may be lowered. If the molybdenum is more than 1.0 wt%, the toughness may be degraded.

(6) V: 1.0 wt% or less

 Vanadium is hard and highly corrosion resistant and does not react with normal acids or alkalis.

Since vanadium has a problem that impact toughness is lowered when it exceeds 1.0 wt%, the content of vanadium is 1.0 wt% or less.

(7) Ni: 4.0 ~ 6.0wt%

Nickel serves to improve the hardenability and corrosion resistance of the steel by making the structure fine and tough, and when coexisted with chromium or molybdenum, it shows excellent hardenability and facilitates heat treatment.

In particular, nickel serves to stabilize the particles to improve impact resistance, and when the nickel content is more than 6.0wt%, the toughness and mechanical properties are deteriorated.If the nickel content is less than 4.0wt%, castability is decreased, and after solidification There is a risk of increased cracking.

(8) Ti: 1.0 wt% or less

Titanium has high strength, rigidity, toughness, and corrosion resistance, but when it exceeds 1.0 wt%, impact toughness is lowered.

(9) Nb: 1.0wt% or less

Niobium does not corrode well with strong acids or bases and has high corrosion resistance, but when it exceeds 1.0 wt%, impact toughness is lowered.

Test Example

Hereinafter, the result (test example) of the comparative test of the corrosion resistance and abrasion resistance of Example 1 of this invention and the comparative example mentioned later is demonstrated.

First, an example of the composition (Example 1) of the cast iron for rotating parts obtained by the Example of this invention is as Table 1 below.

TABLE 1

Table 2 below shows hardness values of the alloy according to Example 1 of the present invention.

This test was conducted by KTR (Korea Institute of Chemical Convergence Testing) and the test method was ASTM E18.

TABLE 2

Table 3 below shows the measured tensile strength of the alloy according to Example 1 of the present invention.

This test was conducted by KTR (Korea Institute of Chemical Fusion Testing), and the test method was ASTM E8 / E8M-16a.

TABLE 3

As a result of the above test, Example 1 of the high chromium cast iron according to the present invention is HRC hardness 50 ~ 60, the tensile strength was satisfied the range of 500 ~ 700MPa.

Table 4 below shows two representative cast iron compositions currently used for general rotating parts as comparative examples.

TABLE 4

In particular, Comparative Example 1 has a relatively low Ni content compared with Example 1, and Comparative Example 2 has a relatively high Ni content compared with Example 1.

Table 5 below is a test result comparing the corrosion resistance of Example 1 of the present invention and the two comparative examples.

This test was carried out by SGS Korea, the test method was carried out by ASTM A262-15 Practice B, the result is a value of the weight loss amount of the test piece before and after the test, the initial specimen weight is 10g The comparative example made the same shape.

The detailed test method is described as follows.

First, as shown in Figure 2a, the initial weight of the specimen is measured.

Next, quantify the test solution in the flask to complete the composition of the test solution.

The composition of the test solution was 236 ml of sulfuric acid (95%), 400 ml of water, and 25 g of ferrous sulfate heptahydrate.

And heating and stirring are simultaneously performed until ferric sulfate powder melt | dissolves completely.

As shown in Fig. 2b, after dissolution, the turbid yellow solution shows clear yellow color.

The acidity of the test liquid may change due to the loss of steam during the heating process, so it is blocked by the cooler.

Corrosion test specimens of defined dimensions are removed by a grinding machine to remove traces from the surface, and then placed separately in a glass container.

Check and record the weight of the specimen before placing it in the glass container.

The test is carried out when the composition of the test solution and pretreatment of the specimen (such as polishing) are completed (see FIG. 2C).

The test is run for 30 minutes, and when the test is complete, remove the glass container from the corrosion solution and clean the specimen.

Specimen cleaning is accomplished by ultrasonic cleaning in water.

2d shows the flask with the test completed.

Dry the specimen well and weigh it.

Comparing the test specimen weight before and after the test completes the evaluation of the corrosion resistance.

TABLE 5

As a result, the average weight loss of Example 1 is 0.4611g, the average weight loss of Comparative Example 1 is 0.7117g, and the average weight loss of Comparative Example 2 is 4.8959g with respect to the same shape having an initial specimen weight of 10g.

Therefore, it can be seen that the alloy of Example 1 having a Ni content of 4.0 to 6.0 wt% has better corrosion resistance than the alloys of Comparative Examples 1 and 2 deviating from Example 1 in Ni content.

Table 6 below is a test result comparing the wear resistance of Example 1 of the present invention and the two comparative examples.

This test was conducted by the Korea Institute of Polymer Testing, and the test method was conducted according to KS D8314, and the result value (mass reduction rate) = (weight before test-weight after test) / weight before test x 100.

The rubbing tester was used to compare the weight before and after the abrasion test. Specific test conditions are as follows.

(1) Tester: Rubbing Tester (NR-BR1)

(2) Load: 500g

(3) wear material: sandpaper # 220

(4) Test speed: 60rpm

(5) Stroke: 50 ± 2mm

(6) Cycle: 7,200 times

(7) Specimen size: 12.48 ± 0.03mm × 25.35 ± 0.03 × 4.00 ± 0.02

(8) Test temperature: (24 ± 2) ℃

(9) Test Humidity (RH): (45 ± 5)%

TABLE 6

As a result of the test, the average mass reduction rate of Example 1 is 0.052%, the average mass reduction rate of Comparative Example 1 is 0.084%, and the average mass reduction rate of Comparative Example 2 is 0.066%.

Therefore, the alloy according to Example 1 having a Ni content of 4.0 to 6.0 wt% shows better wear resistance than the alloys according to Comparative Example 1 and Comparative Example 2, which deviates from Example 1 in Ni content.

For reference, FIGS. 3A to 3F show test reports showing test conditions and test results of the abrasion resistance test performed at the Korea Polymer Testing Institute for Example 1 and Comparative Example 1. FIG.

Thus, according to the present invention, through the Ni content of 4.0 ~ 6.0wt% to ensure excellent castability, corrosion resistance and abrasion resistance, and further comprises titanium, niobium and vanadium components to maintain abrasion resistance and at the same time excellent corrosion resistance It can be used for a long time even in the field where strong acid and base are discharged, thereby extending the replacement cycle of parts and reducing the replacement cost.

Therefore, the high chromium cast iron excellent in the abrasion resistance and corrosion resistance which concerns on this invention can be applied effectively to the mechanical components of the machinery for conveying the substance which has strong acid or a base characteristic.

Embodiments of the present invention are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible within the scope of the following claims.

Claims (2)

C: 1.0-3.0 wt%, Si: 2.0 wt% or less, Mn: 2.0 wt% or less, Cr: 25.0-27.0 wt%, Mo: 0.4-1.0 wt%, V: 1.0% or less, Ni: 4.0-6.0 wt% %, Ti: 1.0 wt% or less, Nb: 1.0 wt% or less, and the balance includes an alloy composition of Fe and other unavoidable impurities,
A high chromium cast iron having excellent abrasion resistance and corrosion resistance, characterized by having a metallic structure consisting of primary austenite and martensite phase-transformed from austenite and residual austenite. delete

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