JPH04254541A - Cobalt-base alloy having corrosion resistance and wear resistance - Google Patents

Abstract

PURPOSE:To produce a Co-base alloy excellent in corrosion resistance, wear resistance, etc., by incorporating specific percentages of Cr, Mo, Si, B, C, Fe, and Ni into Co. CONSTITUTION:A Co-base alloy having a composition consisting of, by weight, 11-20% Cr, 20-32% Mo, 0.5-2% Si, 0.5-2% B, <=0.2% C, <=2% Fe, <=2% Ni, and the balance essentially Co is prepared. By this method, the alloy excellent in wear resistance, corrosion resistance, toughness, etc., can be obtained. By coating the surface, in the region requiring corrosion resistance, wear resistance, etc., of the component members for plastic molding machine and kneading machine with this alloy as a lining material to about 1-10mm thickness, corrosion and wear can be reduced and relieved and the occurrence of cracks, breakage, etc., can practically be prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a plastic molding machine.
This invention relates to a cobalt (Co)-based alloy with excellent corrosion resistance, wear resistance, etc., which is used as a constituent material of 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 alloy for the lining, for example, Cr: 6-12%, Mo: 25-12%
30%, Si: 2-3.5%, balance consisting of Co and impurities, or Cr: 15-20%, Mo: 25-30
%, Si: 3 to 4.5%, the balance being Co and impurities.

[0005]

[Problems to be Solved by the Invention] However, the materials of conventional lining alloys have advantages and disadvantages, and looking at the material properties of the above two types of alloys, the former alloy has good corrosion resistance against various acids. The latter alloy, on the other hand, has high hardness and excellent wear resistance, but has improved corrosion resistance. Moreover, since it has poor toughness, it is prone to cracks and chips during the manufacturing process of parts, especially during machining.

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. To provide a Co-based alloy that has improved corrosion resistance, wear resistance, toughness, etc.

[0007]

[Means and effects for solving the problems] Co of the present invention
The base alloy is Cr: 11-20%, Mo: 20-32%,
Si: 0.5-2%, B: 0.5-2%, C: 0.2%
Hereinafter, it has a chemical composition consisting of Fe: 2% or less, Ni: 2% or less, and the remainder substantially Co.

The Co-based alloy of the present invention having the above-mentioned composition mainly consists of a quaternary alloy phase of Co, Cr, Mo, and Si;
It has a relatively fine multiphase mixed phase structure consisting of a quaternary alloy phase of Co, Cr, Mo, and B containing a trace amount of Si. The quaternary alloy phase of Co, Cr, Mo, and Si provides the alloy of the present invention with a high degree of corrosion resistance and wear resistance.
It is thought that good toughness is imparted by the quaternary alloy phase of r, Mo, and B. In addition, the alloy of the present invention having the above composition has good fluidity in the molten state, and can be used for both spraying and casting of molten metal, and when applied to components of plastic molding machines, etc. A sintering method using the powder as a raw material, a centrifugal coating method using molten metal, etc. 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.

Cr: 11-20% Cr forms the various alloy phases mentioned above together with Co, Mo, B, Si, etc., and has the effect of increasing hardness and corrosion resistance. The reason why the amount added is set to 11% or more is because if it is less than that, the effect of improving hardness cannot be sufficiently expressed. The effect increases by increasing the amount added, but on the other hand, the toughness of the alloy decreases, so the upper limit was set at 20%.

Mo: 20-32% Mo forms the alloy phase with Co, Cr, B, Si, etc.
In addition to strengthening corrosion resistance, especially against oxidizing acids, it also has the effect of increasing hardness. Lower limit of addition amount to 20%
This is because if less than this, the effect of improving corrosion resistance is insufficient, and the effect can be enhanced by increasing the amount, but since excessive addition causes embrittlement of the alloy, it was set at 32%.

Si: 0.5-2% Si lowers the melting point of the alloy and improves the fluidity of the molten metal, thereby improving its sprayability, powder forming properties, and castability. At least 0.5% is required to achieve this effect. However, excessive addition causes embrittlement of the alloy due to the formation and increase of Co-Mo-Cr-high Si phase, so the content should not exceed 2%.

B: 0.5-2% By adding B, a quaternary alloy phase with Co, Cr, and Mo is formed, imparting a high degree of toughness to the alloy. In order to make this effect sufficient, the lower limit of the amount added was set to 0.5%. The effect can be increased by increasing the amount added, but if the amount is too large, the corrosion resistance against oxidizing acids will be impaired, so the upper limit was set at 2%.

Co: Balance component Co, together with the above-mentioned elements, is a basic element for forming the alloy of the present invention, which has both high corrosion resistance and wear resistance, and has high toughness.

C: 0.2% or less, Fe: 2% or less, Ni
: 2% or less C, Fe, and Ni in the alloy of the present invention are not useful elements, and C combines with Cr, Mo, etc., resulting in a decrease in the effective amount of these elements and embrittlement of the alloy due to the formation of carbides. Fe
, Ni cause a decrease in corrosion resistance, so the smaller the amount of these mixed in, the better, but the purpose of the present invention will be lost if C is within 0.2% and Fe and Ni are within 2% each. do not have. Therefore, C is 0.2% or less, Fe and N
The mixture of i is allowed within the range of 2% or less.

It goes without saying that the entire wall thickness of cylinders, screws, nozzles, and other parts that are components of plastic molding machines and kneading machines formed using the alloy of the present invention is not necessarily 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 m.
It may be about m.

[0016]

[Example] Example 1 (I) Production of test material The molten alloy melted in a powder-making high-frequency melting furnace (Ar atmosphere) is pulverized by a centrifugal spray powder mill, and classified to produce sintering raw material powder. . 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 sample sintered alloy. N
o11-14 are invention examples, No.101-108 are comparative examples, and among the comparative examples, No. 101, No. 102 is an example of conventional material, No. 103~No. No. 108 has a composition similar to that of the invention example, but the content of any element (
In the table, the underlined) are examples that deviate 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, make an indentation with a diamond indenter of a Vickers hardness tester, and determine the presence or absence of cracks in the indented part 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 20
If a crack occurs in the indentation when a load of Kgf is applied, 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 displayed as 0 (Kgf), and the toughness index is displayed as 50 (Kgf).
Kgf) means that no cracks occur even if the indenter load is 50 Kgf.

(iii) 10% aqueous hydrochloric acid solution as a corrosion-resistant non-oxidizing acid; 1 as an oxidizing acid;
A prismatic test piece (9 x 9
×7, mm) was suspended and immersed in the test solution, and the corrosion loss (mg) after 24 hours was measured.

[0021]

[Table 1]

In Table 1, invention example No. 11 to 14 and the conventional material No. 101 and no. Comparing No. 102, No. No. 101 shows good corrosion resistance to oxidizing and non-oxidizing acid corrosive liquids, and has a high level of toughness, but has low hardness. Inventive Example No. 102 has high hardness but extremely low toughness and poor corrosion resistance to non-oxidizing acids. 11-14
has good corrosion resistance to oxidizing acids and non-oxidizing acids and high hardness, and despite its high hardness, it also has a high level of toughness, making it the No. 1 conventional material. 101 and no. 102
It combines the advantages of each. In addition, comparative example No.
．． Nos. 103 to 108 have compositions similar to those of the invention examples, but due to excess or deficiency in some of the constituent elements, they have problems with corrosion resistance, hardness, or toughness, and do not have these characteristics. It is not as good as the invention example. That is, No. 103
Although it has high hardness, it has poor toughness and poor corrosion resistance against oxidizing acids.
．． 104 (excessive amount of Cr, C) has sufficient hardness, but lacks toughness and corrosion resistance against non-oxidizing acids; N0.105 (excessive amount of Mo) has high hardness and corrosion resistance. There is no problem with this, but it lacks toughness. Furthermore, No. 10
No. 6 (insufficient amount of B) causes insufficient toughness. 107
(Insufficient amount of Cr) has low hardness, and No. 108 (insufficient amount of Mo) has poor resistance to oxidizing acids. 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 (I) 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 and no. 2
02 is a comparative example (No. 101 in Table 1 of Example 1)
and no. 102). 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.

[0025]

[Table 2]

As is clear from the test results in Table 2, in this example as well, invention example No. 21, No. Comparative Example No. 22 is a conventional material. 201, No. It can be seen that, unlike No. 202, it has good corrosion resistance against oxidizing and non-oxidizing acids, high hardness, and excellent toughness.

[0027]

Effects of the Invention The alloy of the present invention has improved corrosion resistance and wear resistance 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 harsh 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 likely to cause cracks and chips during machining in the manufacturing process of parts, improving manufacturing yield, 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] Cr: 11-20%, Mo: 20-3
2%, Si: 0.5-2%, B: 0.5-2%, C: 0
．． A corrosion-resistant and wear-resistant cobalt-based alloy for plastic molding machines and kneading machines, consisting of 2% or less, Fe: 2% or less, Ni: 2% or less, and the remainder substantially Co.