JPH04254540A - Nickel-base alloy having corrosion resistance and wear resistance - Google Patents

Abstract

PURPOSE:To obtain a nickel-base alloy having corrosion resistance and wear resistance for plastic molding machine and kneading machine by specifying a composition consisting of C, Si, Cr, B, Cu, Fe, and Ni. CONSTITUTION:The alloy is a nickel-base alloy consisting of 0.4-1.2% C, 3-6% Si, 6-16% Cr, 2.5-3.5% B, 1-3% Cu, <=5% Fe, and the balance essentially Ni, used as material for constituting the members for plastic molding machine and kneading machine, and excellent in corrosion resistance, wear resistance, etc., and the durability of the above members can be improved and stabilized by using this alloy. The above alloy has superior toughness, and the occurrence of cracks, etc., can be prevented at the time of manufacturing the members and during use. Moreover, the above alloy has superior flowability as molten metal and both spray pelletization and casting are made possible and further, the sintering characteristics of powder is improved.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a plastic molding machine.
This invention relates to a nickel (Ni)-based alloy with excellent corrosion resistance, wear resistance, etc., which is used as a component material for a kneader.

0002

2. Description of the Related Art Components of plastic molding machines and kneading machines for raw material pellets used for plastic molding, such as cylindrical cylinders, must have wear resistance and corrosion resistance. Conventionally, cylinders made of nitrided steel have been used exclusively as the cylinders.

Recently, in order to meet the demands for flame retardancy and high strength for plastic molded products, flame retardants such as halogen compounds and hard fibers such as ceramics as composite reinforcing fibers have been kneaded into resins. It is being done. As a result, the inner surfaces of cylinders are subject to corrosion due to flame retardants and wear due to hard fibers, and further surface damage is accelerated due to high pressure and high speed molding to improve production, and the conditions of use are becoming more severe. It's coming. Nitriding steel, which has been used conventionally, cannot be expected to adequately cope with such changes in usage conditions.

As a countermeasure to this problem, a so-called centrifugal coating method or a powder metallurgy method is applied using an alloy having corrosion resistance and wear resistance as a lining material, and the inner surface of the cylinder is coated and protected with a corrosion and wear resistance alloy. As the lining alloy, for example, a Co-Cr-Mo-Si based Co-based alloy, a C-containing Ni-Si-Cr-B based Ni-based alloy, etc. are used.

[0005]

[Problems to be Solved by the Invention] However, although the above-mentioned Co-based alloy has good corrosion resistance and toughness, it has low hardness and poor wear resistance, and furthermore, it contains a large amount of expensive metals such as Co and Mo. On the other hand, although the above Ni-based alloy has excellent hardness and toughness and is relatively inexpensive, it has poor corrosion resistance, and particularly has a problem with corrosion resistance to non-oxidizing acids.

The present invention has been made in view of the above, and is effective in improving and stabilizing the durability of cylinders, screws, nozzles, and other related components of plastic molding machines and kneading machines. The present invention provides an improved Ni-based alloy.

[0007]

[Means and effects for solving the problems] Ni of the present invention
The base alloy is C: 0.4-1.2%, Si: 3-6%, C
r: 6-16%, B: 2.5-3.5, Cu; 1-3%
, Fe: 5% or less, and the balance substantially consists of Ni.

The Ni-based alloy of the present invention has excellent wear resistance and toughness, and has hardness and corrosion resistance against various acids. In addition, the alloy of the present invention has good fluidity in the molten state, and can be sprayed into powder from molten metal or cast. When applied to components of plastic molding machines, etc., the powder can be used as a raw material. A sintering method using molten metal or a centrifugal coating method using molten metal can be freely selected depending on the shape of the member and other circumstances. The reasons for limiting the components of the alloy of the present invention are as follows.

C: 0.4-1.2% C forms carbides such as Cr and increases the hardness of the alloy. At least 0.4% is required to achieve this effect. However, adding a large amount impairs the toughness of the alloy, so 1.2
The upper limit is %.

Si: 3 to 6% Si increases the fluidity of the alloy in a molten state, improves its sprayability, powder forming properties, and castability, and is effective in improving the sinterability of the alloy powder. Furthermore, Si acts as a solid solution in the base to increase the hardness of the base. The lower limit of the addition amount is set at 3% in order to ensure good spraying/powdering properties and castability, and to obtain a solid solution hardening effect of the base. The effect can be increased by increasing the amount added, but since adding a large amount causes significant embrittlement of the alloy, the upper limit was set at 6%.

Cr: 6-16% Cr forms hard carbides and borides and increases the hardness of the alloy. Furthermore, addition of Cr is effective in improving corrosion resistance. Addition of at least 6% is required to ensure these effects. Increasing the amount added increases the above effects, but on the other hand, it lowers the toughness of the alloy and impairs powder forming properties, so it is set at 16%.

B: 2.5 to 3.5% B has the effect of increasing the fluidity of the molten alloy, improving the spraying/powder forming properties and castability, and improving the sinterability of the powder. Further, B forms a boride of Cr as described above, and contributes to improving the hardness of the alloy. The lower limit of the addition amount was set at 2.5% because if it is less than that, the hardness improvement effect will be insufficient and the sinterability of the alloy powder will also deteriorate, and excessive addition may cause the alloy to become brittle. Therefore, the upper limit was set at 3.5%.

Cu: 1-3% Cu forms a solid solution in the matrix and is extremely effective in improving corrosion resistance, especially sulfuric acid corrosion resistance. In order to ensure this effect, the amount added was set to 1% or more. However, if added in a large amount, the hardness decreases, so the upper limit was set at 3%.

Fe: 5% or less Fe is an element that accompanies it as an impurity, and its presence in large amounts causes a decrease in corrosion resistance, but if it is within the range of 5%, there is no substantial effect. It was decided that mixtures would be allowed with an upper limit of %.

Ni: Balance component Ni is a basic component that forms the alloy of the present invention, which, together with the above-mentioned elements, has corrosion resistance, wear resistance, and toughness.

It goes without saying that the entire wall thickness of cylinders, screws, nozzles, and other components of plastic molding machines and kneading machines that are formed using the alloy of the present invention does not need to be made of the alloy of the present invention. The alloy of the present invention may be applied as a lining material to the surface of areas requiring corrosion resistance, wear resistance, etc., using a metal block made of structural steel or the like in a desired shape according to the intended member as the base material. The alloy of the present invention may be powdered by centrifugal spraying, for example, and the powder classified to an appropriate particle size may be used as a sintering raw material to form a sintered alloy layer covering the surface of the base material. If it is a single-axis cylinder, etc., apply the centrifugal coating method, rotating the cylindrical base material around the horizontal axis,
A molten metal of the alloy of the present invention may be injected into the hollow hole, and an alloy layer may be formed on the inner circumferential surface of the cylindrical base material under the action of centrifugal force. The thickness of the coating alloy layer is, for example, 1 to 10 mm.
It may be of a certain degree.

[0017]

[Example] Example 1 (I) Production of test materials Molten alloy melted in a powder-making high-frequency melting furnace (Ar atmosphere) is powdered using a centrifugal spray powder mill, and classified to produce sintering raw material powder. do. Particle size: 53-250 μm. A sintered steel can (inner dimensions: φ52 x 201, mm) and a lid are used as canning materials, the above powder is put in, the lid is placed in a vacuum, and the lid is sealed by welding, followed by hot isostatic pressure sintering. It was attached to. Processing temperature: solidus temperature, pressure: 1500Kgf/cm
2. Time: 2 hours. After the treatment was completed, the canning material was removed by machining, and a disk-shaped sintered alloy block was collected.

Table 1 shows the chemical composition of the sintered alloys tested. N
o. Nos. 11 to 14 are invention examples, No. 101 to 106 are comparative examples, and among the comparative examples, No. 101 is an example of conventional material,
No. 102~No. 106 has a composition similar to the invention example, but the content of any element (underlined in the table)
This is an example that deviates from the provisions of the present invention. The right column of the same table shows the results of the following tests obtained for each sample material.

(II) Material properties (i) Hardness: Rockwell C
Measured on a scale. The numerical value in the "Hardness" column in the table shows the average value at five locations.

(ii) Using the board surface of the tough sintered alloy block as the test surface, indentation is made with a diamond indenter of a Vickers hardness tester, and the presence or absence of cracks in the indentation portion is determined by microscopic observation (magnification: 200). . The indenter load (Kgf) is 1, 5, 10, 20,
There were six levels: 30 and 50. The numerical value in the "Toughness Index" column in the table represents the maximum load (Kgf) that does not cause cracks. For example, there is no crack in the indentation when the indenter load is 1Kgf, 5Kgf, and 10Kgf, and there is no crack at 20Kgf.
If a crack occurs in the indentation under a load of gf, the toughness index is indicated as 10 (Kgf). Similarly, when a crack occurs in an indentation with an indenter load of 1 Kgf, the toughness index is shown as 0 (Kgf), and the same index is 50 (Kgf).
) means that no cracks occur even if the indenter load is 50 kgf.

(iii) Corrosion resistance A 10% aqueous solution of hydrochloric acid and a 10% aqueous sulfuric acid solution as a non-oxidizing acid, and a 10% aqueous solution of nitric acid as an oxidizing acid (both at a temperature of 50° C.) were used as test solutions to test the sintered alloy. A prismatic test piece (9 x 9 x 7, mm) cut out from the block was suspended and immersed in the test solution, and the corrosion loss (mg) after 24 hours was measured.

[0022]

[Table 1]

In Table 1, invention example No. 11 to 14 and the conventional material No. Comparing No. 101, No. 10
Although Invention Example No. 1 has good hardness and toughness, it has poor corrosion resistance, especially corrosion resistance to non-oxidizing acids. Nos. 11 to 14 have a high degree of corrosion resistance against oxidizing acids and non-oxidizing acids, and also have excellent hardness and toughness. Note that Comparative Example No. Nos. 102 to 106 have compositions similar to those of the invention examples, but because some of the constituent elements are in excess or deficiency, they have problems in corrosion resistance, hardness, or toughness, and they do not have these characteristics. It is not as good as the invention example. That is, No. No. 102 (insufficient amounts of C, Si, and B) has a significant lack of hardness. 103 (excessive amounts of C and B) and No. No. 104 (excessive amount of Si) has high hardness but poor toughness. 105(C
r, insufficient amount of Cu, excessive amount of Fe) has poor corrosion resistance and insufficient hardness. 106 (excessive amount of Cr) has excellent hardness and corrosion resistance, but has insufficient toughness. From these facts, it can be seen that in order to obtain a sufficient improvement effect on all of the various properties of corrosion resistance, hardness, and toughness, the composition of ingredients prescribed by the present invention must be satisfied.

Example 2 (1) Production of test material Molten alloy melted in a high frequency melting furnace (Ar atmosphere) was
It was cast into a steel mold (inner dimensions: 50 x 50 mm, rectangular type) in an atmosphere of r, and after solidification was completed, it was taken out from the mold and machined to obtain a rectangular disc-shaped block (wall thickness 15 mm). .

Table 2 shows the chemical composition of the test materials. No. 2
1.No. 22 is an invention example, No. 201 is a comparative example (same material as No. 101 in Table 1 of Example 1). Hardness measurements, toughness evaluations, and corrosion tests similar to those in Example 1 were performed on each sample material, and the results shown in the right column of the table were obtained.

[0026]

[Table 2]

As is clear from the test results in Table 2, in this example as well, invention example No. 21, No. 22 is a conventional material No. It can be seen that, unlike No. 201, it has good corrosion resistance against oxidizing and non-oxidizing acids, high hardness, and excellent toughness.

[0028]

[Effects of the Invention] The alloy of the present invention has high corrosion resistance, wear resistance and toughness required for plastic molding machines and kneading machines. By applying the present invention alloy to these parts, corrosion and wear of the parts can be reduced and alleviated due to severe usage conditions such as kneading of flame retardants and reinforcing fibers into resin, and high-pressure and high-speed molding. In addition, since it has high hardness and excellent toughness, it is less prone to cracks and chips during machining in the manufacturing process of parts, improving manufacturing yields, and is also highly resistant to cracks and chips during actual use. It has high resistance and can be used stably, providing effects such as improved durability, reduced maintenance, and increased productivity in plastic molding and kneading processes.

Claims (1)

[Claims] [Claim 1] C: 0.4-1.2%, Si: 3-6
%, Cr: 6-16%, B: 2.5-3.5, Cu: 1
Corrosion-resistant and wear-resistant nickel-based alloy for plastic molding machines and kneading machines, consisting of ~3%, Fe: 5% or less, and the balance substantially Ni.