JPS5814871B2 - Boron-containing high-silicon heat-resistant steel - Google Patents

Description

[Detailed Description of the Invention] This invention is an improvement of heat-resistant steel that can be forged and forged.
This is related to this.

The inventor has already developed a high-silicon self-fluxing alloy for surface hardening that has been endowed with abundant toughness and great wear resistance, and has patented patent No. 750.
A patent was obtained as No. 750 (Japanese Patent Publication No. 49-11131).

That is, the high-silicon self-fluxing alloy for surface hardening according to the above patent has C0.06% or less, Si 4-8%, M, n 1
~3%, Ni6~14%, Cr12~24, Mo, W
and B in 1 to 3 parts each, V, Nb, Cu, and Co in 2% or less each, A1 and T1 in 1 part or more each,
The balance is made of Fe, and is characterized in that the sum of the Ni and Mo contents is twice the Si content, and the Cr content is three times the Si content.

However, although this type of alloy has excellent wear resistance and corrosion resistance, it has the disadvantage that it cannot be used as cast and forged steel material (hereinafter simply referred to as steel material).

The reason for this is that the patented invention alloy has a low melting point and extremely high hardness.

This indicates that this kind of metal cannot be forged and cannot be used as a steel material.

In addition, in order to be used as a steel material, it is necessary to have a certain degree of toughness, and the alloy with the lowest elongation value among heat-resistant cast steel products is JIS G5122SCH15, which has an elongation of 4%.

Therefore, the present inventors conducted various studies in order to obtain an industrial material that is suitable for use at high temperatures and that can be forged and cast. By determining the correlation between the limit that allows this and the limit that ensures elongation as a cast material, boron compounds in the steel can be generated and dispersed to provide the desired strength. 2. I discovered that it is possible to obtain industrial materials.

Furthermore, Si is an element that significantly increases hardness, and Ni
is the element that has the greatest effect on its reduction, so in order to obtain steel suitable for use as the above-mentioned industrial material, it is necessary to adjust the content of Si and Ni to reduce hardness and impart toughness. It turned out that it was necessary to do so.

Therefore, an object of the present invention is to provide a boron-containing high-silicon steel that has excellent heat resistance, wear resistance, and corrosion resistance and can be forged and cast.

In order to achieve the above object, in the present invention, C0.0
6% or less, Si 3-5%, Mn 2% or less, Ni 16-2
4%, Cr12-24%, MO, W1-3%, B0.3
~1%, V, Nb and Co2% or less, A1 and Til%
Hereinafter, the remaining portion is characterized by consisting of Fc.

Next, examples of the boron-containing high-silicon heat steel according to the present invention will be explained.

Table 1 shows the chemical components of two typical examples of the present invention, and as a comparison example, Patent No. 750750 (Japanese Patent Publication No.
The chemical composition of the high-silicon self-fluxing alloy for surface hardening according to Publication No. 131 is shown below.

Furthermore, Table 2 compares the mechanical properties of the invention steels (5) and (B) and a control example.

From the above results, it was confirmed that the steel A of the present invention can be forged at 1050°C, and the steel B of the present invention is difficult to forge.

Therefore, it was confirmed that when used as a forging material, the boron content significantly affects its workability.

Furthermore, although steel B of the present invention cannot be forged, it can be fully utilized as a casting material because of its large elongation value in a tensile test.

However, the hardening alloy for surface hardening of the control example has such high hardness and low toughness that a tensile test cannot be performed.

This is a natural result for a self-fluxing alloy.

From the above, in the present invention, the boron content is
The lower limit was set within the range where forging would be acceptable, and the upper limit was set within the range where it could not be produced industrially as a forged product, but could be used as a cast product, and the elongation of the cast product was guaranteed.

In addition, in the present invention, since Si is an element that significantly increases hardness and Ni is effective in reducing hardness, it imparts hardness and toughness suitable for use as a steel material. In order to obtain
The content was defined as 16 to 24 inches.

Furthermore, in the present invention C, since the present invention is a high-silicon steel and Cr is effective in oxidation resistance like Si, a content of 12 to 24% is sufficient, and Patent No. 7507
Same as No. 50.

Mo, W, V, Nb, AA and Ti are all A3
It is known as an element that increases the transformation point.

The present invention is a high-silicon steel characterized by boron content, and boron is present in the steel and tends to generate chromium boride, which has the effect of reducing the amount of chromium and lowering the A3 transformation point.

This is effective, for example, for lowering the A3 transformation point of alloys as described in Japanese Patent Publication No. 46-9536, but as in the high-silicon steel of the present invention, the action of silicon is affected by nickel, manganese, etc. If the A3 transformation point is adjusted, it is necessary to adjust the decrease in the A3 transformation point due to the addition of boron by using an element that increases the A3 transformation point.

In this sense, Mo, W, V, Nb, A, g, and Ti are effective because they raise the A3 transformation point, resulting in offsetting the effect of boron.

Therefore, in the present invention, Mo and W are added as essential elements for adjusting the A3 transformation point.

This is because Mo and W are known to be effective elements for improving high-temperature strength, but adding more than a certain amount will raise the A3 transformation point to 750°C or higher, so the upper limit has been set to 3.
%.

V, Nb, At, and Ti are components that allow the alloy of the present invention to be widely used in corrosion-resistant, wear-resistant, and heat-resistant applications;
b improves wear resistance, while AA and TI improve heat resistance, so appropriate amounts of these elements are added depending on the purpose of use.

However, adding more than a certain amount will similarly raise the A3 transformation point to 750°C or more, so
For this reason, the upper limit was set at 2%, and for kl and Ti, the upper limit was set at 1%.

Co is known as an element that improves the high-temperature strength of steel without impairing its toughness, but its effect is relatively slow.

In the present invention, since cobalt is an expensive element, the upper limit is set at 2% with the aim of increasing the high temperature strength by about 10 times.

The alloy according to the present invention has strength comparable to conventional 16-25-6 alloy and N-155LC alloy in various tests at 800°C.

The high-temperature strength of conventional 16-25-6 alloys is largely due to the reinforcement of carbides, but the present invention is mainly characterized by dispersing boron compounds.

Therefore, the alloy according to the present invention is obtained by the N-155 strengthening method using carbide dispersion, which is adopted in general heat-resistant steel.
It has high-temperature strength comparable to LC alloy, JIS G5122SCH15 alloy, etc.

The preferred embodiments of the present invention have been described above, and the alloy according to the present invention has excellent heat resistance, wear resistance, and corrosion resistance.
It can be suitably used as a cast and forged steel material, and since it is a high-silicon steel, it is effective in carburizing and nitriding resistance, and can be widely applied as a heat-resistant cast and forged steel product for industrial furnaces.

Claims (1)

[Claims] IC 0.06% or less, Si 3-5%, Mn 2% or less, Ni 16-24%, Cr12-24fO, Mo and W1-3, B03-1%, V, Nb and Co2
% or less, A1 and Ti 1% or less, and the balance is Fe.