JPS62167834A - Wear and corrosion resistant ni base alloy for centrifugal covering - Google Patents

Abstract

PURPOSE:To obtain the titled alloy superior in solidifying characteristic and corrosion resistance, by restricting contents of Si and Mn, in the title alloy contg. prescribed ratios of B, Si, C, Cr, Mn and Mo in addition to Ni. CONSTITUTION:The Ni base alloy for centrifugal covering is composed of, by weight 2.0-4.5% B, 0.3-1.5% C, 5.0-20.0% Cr, 7.0-20.0% Mo, <=0.4% Si, <=0.4% Mn and the balance Ni. If melting and casting are carried out without adding Si, Mn in such a way, ingot having remarkably improved corrosion resistance in addition to soundness without being badly affected in hardness and temp. during solidification is obtd. The Ni base alloy has equal or better wear resistance compared with conventional Ni and Ni-Co base alloy, and the solidifying characteristic and corrosion resistance remarkably that of exceed the conventional alloy.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a wear-resistant and corrosion-resistant alloy that is used by being coated by a centrifugal coating method on the inner surface of a cylindrical cylinder of a plastic molding machine, etc., which is easily subject to abrasion and corrosion. It is something.

[Conventional technology]

The inner surface layer of a cylinder for a plastic molding machine requires an alloy material that has both corrosion resistance and wear resistance in order to prevent corrosion and wear caused by the resin during molding or additives added to the resin.

Although conventionally known wear-resistant alloys, such as iron-based alloys, are inexpensive, they cannot be used for molding plastics, which require wear resistance and corrosion resistance, which have increased significantly in recent years.

In order to solve this difficulty, various alloys have been developed as adherend alloys for centrifugal coating.

However, among these alloys, Co-based alloys and Co-Ni-based alloys have excellent wear resistance, but in recent years, users have become more demanding in terms of corrosion resistance, and these alloys are becoming insufficient.

In addition, Ni-based alloys, which are known as wear-resistant and corrosion-resistant alloys, have superior corrosion resistance compared to Co-based and Go-Ni-based alloys. Unsuitable for use due to either or both of its properties and coagulation properties. Here, the solidification characteristic means the solidification zone temperature, that is, the difference between the solidification start temperature and the solidification end temperature obtained by subjecting the alloy to differential thermal analysis. If it is too wide, there will be many unhealthy parts on the inner surface of the cylinder during centrifugal casting, and cutting will have to be carried out deeply, which will reduce the material yield and impair economic efficiency, so a narrower one is preferable.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a Ni-based alloy for centrifugal coating that has better solidification properties and corrosion resistance.

In order to achieve this objective, the inventors have conducted repeated research and
, we have found that it is effective to add and contain Si, C, Cr, Mn, and Mo, and have already proposed it (Japanese Patent Application No. 60-2
No. 28885). Furthermore, subsequent research revealed that among the above elements, St and Mn, which were thought to be effective in increasing hardness and deoxidizing, surprisingly did not work sufficiently and also decreased corrosion resistance. I obtained this knowledge. That is,
The ingot obtained by melting and casting without adding Si+Mn was not only sound, but also had no adverse effects on its hardness or solidification zone temperature, and its corrosion resistance was significantly improved.

[Means for solving the problem] As a result, the alloy of the present invention has a B2. 0-4.
5%, C0.3-1.5%, Cr5.0-20.0%,
Mo 7.0-20.0%, Si 0.4% or less, Mn0
．． The composition was made up of 4% or less, the balance being Ni and unavoidable impurities.

[For production]

The reason for limiting the composition of the alloy of the present invention will be described below.

Hereinafter, % represents weight %.

B reacts with Cr to increase the hardness and at the same time lower the solidification initiation temperature. However, if it is less than 2.0%, it will not contribute much to increasing hardness, and if it exceeds 4.5%, it will make the material brittle. C is Cr
It has the effect of increasing hardness by reacting with This effect is 0.3
If it is less than 1.5%, no effect is observed, and if it exceeds 1.5%, R becomes dangerous. Cr reacts with C and B to form carbides and borides, contributing to an increase in hardness. If it is less than 5.0%, no effect will be observed, and if it is added in excess of 20.0%, the effect will be weakened and at the same time the fluidity of the molten metal will be reduced. Mo has the effect of improving corrosion resistance, and if it is less than 7.0%, it has no effect, and if it is contained in more than 20.0%, the coagulation properties deteriorate. It is preferable that St and Mn not be contained;
Even if it is contained, it needs to be 0.4% or less. If at least one of them exceeds 0.4%, the spread of the solidification zone temperature and the decrease in corrosion resistance cannot be ignored.

〔Example〕

Next, the alloy of the present invention will be explained based on examples.

10 kg of each of the present invention alloy, comparative alloy, and conventional alloy were melted in a high-frequency atmospheric melting furnace to form rod-shaped castings.

The ingredients and composition (%) of these alloys are shown in Table 1.

Next, a test piece with a diameter of 411 m and a length of 51 m was taken from a portion of each alloy and subjected to differential thermal analysis. The test conditions were to place the sample in an alumina crucible and heat it at 900°C in an argon cloud.
The temperature is increased at a rate of 10℃ per minute from 900℃ to 1.200℃.
℃ at a rate of 2° C. per minute, and the solidification completion temperature was determined.

Next, the temperature was lowered from 1.200°C to 900°C at a rate of 2°C per minute to determine the solidification start temperature, and the solidification zone temperature was determined from this difference.

In addition, after cutting the rod-shaped casting, embedding it in resin, and finishing the surface by alumina buffing, the Vickers hardness (load 10
kg) was measured. The results of Vickers hardness and solidification zone temperature of each sample are shown in Table 2.

Table 2 Furthermore, cylindrical corrosion test pieces with a diameter of 20 mm and a thickness of 5 mm were prepared from each casting. The corrosion test was carried out using butic acid (concentration 46%).
) in a boiling liquid containing 10% hydrochloric acid (concentration 36%) for 24 hours, and the weight loss per unit area was determined from the weight change before and after the test.

The results obtained are shown in Table 2.

The conventional alloy is the current Ni--Co based alloy, but the alloy of the present invention has the same or higher hardness and has high wear resistance. The narrower the solidification zone temperature, the better, for example 30℃
The alloy of the present invention has a narrower solidification zone temperature than conventional alloys.

Furthermore, the corrosion resistance of the alloy of the present invention is significantly improved compared to conventional alloys.

〔Effect of the invention〕

As detailed above, the alloy of the present invention is similar to conventional C.

It has wear resistance equivalent to or better than Ni--Co based alloys, and its solidification properties and corrosion resistance greatly exceed those of the conventional alloys. Therefore, the number of minute cranks generated on the inner surface during centrifugal casting is significantly reduced, which improves the material yield, and also sufficiently suppresses wear and tear caused by corrosion, which is extremely likely to occur in plastic molding cylinders and the like.

Claims (1)

[Claims] (1) In weight%, B2.0-4.5%, C0.3-1.
5%, Cr5.0-20.0%, Mo7.0-20.0
%, Si 0.4% or less, Mn 0.4% or less, balance Ni and unavoidable impurities.
i-base alloy.