JPS60162749A - Wear resistant cast iron containng much vanadium - Google Patents

Abstract

PURPOSE:To obtain the titled cast iron having high hardness and wear resistance without carrying out heat treatment by regulating a composition consisting of C, Si, Mn, Cr, Nb, V and Fe and the relation between components in the composition. CONSTITUTION:This wear resistant cast iron contg. much V consists of, by weight, 2.5-3.5% C, 0.5-1% Si, 0.5-1.5% Mn, 10-23.5% Cr, 0.5-2% Nb, 3- 8% V and the balance essentially Fe and satisfies V/C=1-2.3 and Cr/C=3.3- 6.7. Since much harder V carbide as well as hard carbide (FeCr)7C is precipitated in a dispersed state, the cast iron has remarkably improved wear resistance. The cast iron is provided with >= about 60 Rockwell hardness as cast, so when it is used used as the material of a mill for grinding ore, rock, coal or the like, the operation cost can be considerably reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high vanadium-containing wear-resistant cast iron for grinding mills for ore, coal, rock, etc., segments, parts for dredgers, parts for iron-making machinery.

Conventionally, the worn portion is coated with, for example, C2, 7 to 3.5%.
, Ni4. Q 5.0%, Or 2.0~5.
N1eOr white cast iron such as hard cast iron consisting of 0%, high Or white cast iron, etc. are used. Ni-0
R-based white cast iron has carbides (FeO
r), G (micro Vickers hardness H 970) is precipitated, whereas high Or white cast iron;, c [micro Vickers hardness HV) 1400]' It is precipitated in

Therefore, since high-Or white cast iron has higher hardness and better wear resistance than Ni-Or cast iron, high-Or cast iron is used in areas that are subject to severe wear.

The composition and hardness of high-Or type white cast iron are as shown in Table 1 according to M8TM Standard A5S2-67. However, when high Cr white cast iron is cast, austenite undergoes pearlite transformation during cooling, resulting in low hardness and poor wear resistance. Therefore, as shown in Table 1, after casting, after heating to 950 to 1,120°C,
It is used as a base site. For this reason, in large thick rolls and the like, there are cases where residual stress is generated during cooling. Furthermore, since the heat treatment is performed at a high temperature of 950 to 1,120°C, deformation and oxidation may occur. In addition, there is a residual austenite phase in the hardened wave caused by rapid cooling,
-so It is necessary to convert the austenite phase into martensite by low temperature treatment at 5=60°C to obtain the highest hardness.

In recent years, there has been a strong demand for improvements to plants with low operating costs that do not require maintenance and inspection over a long period of time when it comes to wear parts such as crushing barrels.

This maintenance and inspection mainly involves machining corrections and replacements due to wear of wear parts using hard cast iron and high-Or white cast iron. Under these circumstances, the wear resistance of conventionally used hard cast irons and high-Or white cast irons is not sufficient, and it is desired to develop high-Or cast irons that have even better wear resistance.

The present invention relates to high vanadium-containing wear-resistant cast iron with high hardness and wear resistance without heat treatment.

That is, the present invention is based on 1 weight, C2,5-3,5%
, 8i 0.5-1%, Mn 0.5-1.5%,
Orl 0 S25.5%, NbO, 5-2%,
V5-8% and 5 parts consisting essentially of Fe;
It is characterized by Vlo 1-2.5, 0r70 5.5-6.7. Concerning wear-resistant cast iron containing high vanadium content.

In addition to the carbides ((FeCr), O, HV 1400) found in conventional high-Or white cast iron, the cast iron of the present invention contains
From precipitating V carbide (Iff2800),
It has significantly improved wear resistance. That is, when vanadium is added to high Or white cast iron, (Fe c
r)yc When VC carbide, which is harder than carbide, precipitates, K and martensitic transformation temperature also change. Vanadium-free high-Or white cast iron contains a large amount of austenite when it is cast. Therefore, in order to reduce the amount of austenite and precipitate (FeOr), 0, and V carbides, it is necessary to strictly adjust the contents of vanadium, carbon, and carbon.

Therefore, the present invention adds vanadium that forms carbide VC to high-Or cast iron with a limited chemical component in a fixed ratio of the amount of chromium and the amount of base element in the limited component, and disperses and forms vanadium carbide. It is characterized by: The high-vanadium-containing wear-resistant cast iron of the present invention has a Rockwell hardness of 60 or more and has excellent wear resistance as cast. Due to these excellent properties, the high-vanadium-containing wear-resistant cast iron of the present invention can be applied to mills and segments for crushing ores, rocks, and coal, parts for dredgers, parts for iron-making machinery, and the like.

Next, the constituent components of the cast iron of the present invention and the amounts added thereof will be explained. Note that in the following explanation, the bar (/) indicates it spurt.

(11G 2.5-3.5% C is an element that has a significant effect on the hardness, wear resistance and toughness of the material of the present invention. If C is less than 2.5%, the hardness and wear resistance On the other hand, there is a problem that the amount of crystallized carbides that contribute to this decreases.

If C exceeds 3.5%, hardness does not change much and toughness decreases, which is not desirable.

(21810, 5-1% If the amount of Si added is less than 0.5%, deoxidation will be insufficient, the castability will be poor, and shrinkage cavities will occur. On the other hand, if it exceeds 1%, the toughness is significantly reduced. Therefore, 8
The amount of 1 added is preferably 0.5 to 1%.

(31Mn O, 5-1,5% Mn is an element that exerts deoxidation and sulfur fixation effects. For this effect, a minimum addition of 0.5% is required. On the other hand, Mn If it exceeds 1.5%, the crystal grains become coarse and the impact value decreases significantly.
The amount of addition is preferably 0.5 to 1.5%.

(410r 10-23.5% Or is an element that exhibits a great effect on improving hardness, wear resistance, and toughness. If its addition amount is less than 10%, it will become a 50 II compound with low hardness. (F19Or) 705, which increases the amount of
Since the amount of carbides decreases, sufficient wear resistance cannot be obtained. On the other hand, when it exceeds 23.5%, (yscr), c,
In addition, it reduces wear resistance (F 6 cr)2
5c6 carbide crystallizes, reducing wear resistance. Therefore, the amount of Or added is preferably 10 to 25.5%.

(51Wb O, 5-2% Nb is an element that precipitates Nb carbide with high hardness (Mike 4 Vickers hardness HV) 205ω and improves wear resistance. In order to exhibit this effect, k must be at least 0.5%
is necessary. Also, regarding the upper limit of the amount of added vanadium, as the amount of Nb increases, the amount of vanadium added is limited.
2%.

(6) v 5-8% V has a very strong tendency to form carbides and produces VC carbide (HV2800) showing very high hardness, so it is an extremely effective element for improving wear resistance. As for the amount of addition, K, which precipitates carbide VC, reduces the amount of retained austenite, and improves hardness and wear resistance, needs to be added in an amount of 6% or more, whereas when V exceeds 8%, , carbide vO
The amount of V added is 3.
It is preferable to set it to 8%.

The excellent properties of the material of the present invention cannot be obtained by using only any alloy within the above-mentioned chemical composition range. Among the chemical components, vanadium precipitates carbide VC and becomes hard as cast.
Although it is the most important element for obtaining 6o or more, its amount needs to be determined by the amounts of C and Or. That is, when the added vanadium precipitates carbides VQ and L', the carbon concentration in the base decreases, which affects the precipitation of (Fear) 70 and the martensitic transformation point of the base. If the amount of vanadium added exceeds the appropriate amount for the amount of carbon, even if carbide VC is precipitated, the amount of carbon dioxide is reduced and the hardness of the base is also lowered.

Therefore, the overall hardness and wear resistance will be reduced. There is a correlation between the wear resistance and hardness of these high Or cast irons, and it can be considered that the higher the hardness, the better the wear resistance. Further, at this time, the hardness is influenced by the hardness of both the precipitates and the base structure of the high-Or white cast iron, and the higher the hardness of both, the better the wear resistance.

Therefore, Tables 2 and 3 and Table 1 show the results of tests in which the ratios of the main elements vanadium, chromium, and carbon, which dominate the precipitate and matrix structure, were varied within the above-mentioned chemical composition range.
As shown in the figure.

As shown in Table 3, alloys that can obtain a Rockell hardness (HRo) of 60 or higher have a vanadium (%)/carbon (%) addition weight ratio of 1 to 2.3 within the above chemical composition range, Furthermore, the weight ratio of weight (%)/carbon (%) added is 5
．． It can be seen that conditions 5 to 6.7 must be satisfied.

The present invention materials A1-410 alloys shown in Tables 2 and 3 satisfy the above ratio, and the A11 alloys shown as comparative materials
~l6L16 alloy is an alloy with the above ratio outside the present invention, and has a significantly low HRO hardness of 38 to 57. Also, 417
and AI8 alloy are conventionally used hard cast iron and high-Or white cast iron. It has an excellent hardness of HRo) 60 compared to
It can be seen that it has good strength and toughness and is fully suitable as a wear part.

Furthermore, the wear test results for the A3 alloy of the present invention material, the comparative material 412 alloy, the conventional material two-node cast iron (417), and high Or cast iron (418) K in Tables 2 and 3 are shown in the fourth table. Shown in the table. In this abrasion test, silica stones having a particle size of 2 to 5 cm were rotary crushed for 10 hours, and their abrasion resistance was compared based on the abrasion loss.

Table 4 Rotary crushing in silica for 10 hours From Table 4, the hardness of the present invention material I63 alloy, in which hard carbide VC was precipitated, was higher than the comparison material (A12),
It can be seen that the wear resistance is superior to conventional materials (A17 and A18) K.

As described above, the high vanadium-containing wear-resistant cast iron of the present invention is
2. It has significantly better wear resistance than conventional hard materials, and
As cast, it has approximately the same hardness as high-Or cast iron that has been subjected to conventional t050C hardening heat treatment, and has excellent wear resistance.

Therefore, if the material of the present invention is used for grinding mills for various ores, coal, rocks, etc., parts for iron-making machinery, and parts for dredgers, it will have better wear resistance than conventional products, so it will need to be replaced more frequently due to wear than conventional products. can be significantly reduced. As a result, maintenance and inspection of the plant can be omitted for a long period of time, resulting in a significant reduction in operating costs.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the addition amount ratio of lithium/R element, the addition amount ratio of vanadium/carbon, and hardness.

Claims (1)

[Claims] Based on one base, C2.5-5.5%, 810.5-1%
. MnO, 5-1,5%, Or 10-2 L5%,
NbO, 5-2%, Y3-8% and the balance essentially composed of Fa, Vlo 1-2.5.0r703
．． 5-6.7. High vanadium content wear-resistant cast iron.