JPS5910990B2 - Ferritic stainless steel with excellent rust resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferritic stainless steel with excellent rust resistance, and is intended to provide a steel plate for use in kitchen appliances, bathtubs, and the like.

The environment used for kitchen appliances such as sinks and microwave ovens is C.
There are many opportunities to come into contact with moisture and water, and there are many cases where people are placed in harsh conditions such as bathtubs where they repeatedly dry and wet. The main form of corrosion in such an environment is the formation of red rust due to manganese sulfide, etc. In particular, when the Ct content is high, the passive film unique to stainless steel is easily destroyed, and as a result, manganese sulfide comes into direct contact with moisture This often becomes the starting point for rust. Currently, as a preventive measure against the occurrence of rust, the current situation is to change the sulfide form to (Mn, Cr)S, etc., and consider the balance of the components so that they are insoluble in water. When the amount of Mn is varied, the precipitated (Mn, Cr)S tends to change to MnS with a low Cr content, and there are many opportunities for rust to occur.

Furthermore, even at present, sufficient rust resistance is not necessarily achieved. The present invention is a ferritic stainless steel that has been improved so that it always has excellent rust resistance even when the Mn content changes greatly, and has better rust resistance than the current SUS4300 level, and is suitable for use in the above-mentioned corrosive environment. Regarding steel that has excellent rust resistance, as well as the necessary mechanical properties and economic efficiency depending on the application, C: 0.00
1~0310%, Si■ 0.05~1.0%, Mn■
0.1~2.0%, Cr■ 15.0~20.0%,
S ■ 0.001-0.02 article, Ce: 0.01-1
The first invention is a stainless steel plate containing 80% of the stainless steel and the remainder consisting of iron and unavoidable impurities and substances. Furthermore, the above-mentioned stainless steel of the present invention may contain Ti, NbtMol, etc. as necessary.
One or more of B may be added, and in this case, the stainless steel has a content of 0001 to 100% for one or more of Ti and Nb, and 0.01 to 100% for Mo.
5.0%, including 0001 to 0005% for B,
The remainder consists of iron and unavoidable impurities.
Invented steel.

Conventionally, there have been inventions and reports by the present inventors of adding Ce to mild steel plates for automobiles and materials for cans, as examples of improving rust resistance in environments containing moisture by adding elements in steel.
There is no example in which Ce is applied to high chromium ferritic stainless steel for steel plates as in the present invention.

In principle, as in the case of ordinary steel, αMnS, which is soluble in water, is
By adding e, water-insoluble Ce-containing sulfide or C
It is distinctive in that it has been changed to an e-containing oxysulfide. In particular, the present invention suppresses the formation of MnS even if the Mn content is higher than the standard for normal SUS43O, and even when Ti is added, instead of Ti2S3 [Ce-containing sulfide, Ce-containing oxysulfide] The fact that these substances are preferentially generated is the main reason for improving rust resistance. It is also a fact that cannot be overlooked that the addition of Ce promotes the desulfurization effect and lowers the amount of S in the steel. That is, the major feature is that the sulfide produced is also insoluble in water at the same time as the amount of S is reduced. The details will be described below, as well as the reasons why the component ranges of the present invention were determined as described above. C
is generally an essentially important component in the production of steel, and depending on the amount of this component, the structure of steel changes to martensite, ferrite, or austenite. In the present invention, in order to achieve corrosion resistance and rust resistance as well as a ferrite structure, the content is limited to <0.10% or less. Also, the reason for limiting it to 0.00i% or more is 0.
．． This is because if the content is less than 00i%, economical smelting cannot be achieved. The reason why the amount of Si is limited to 0.05% to 1.0% is the same as the reason why the amount of Mn is limited to 0.1 to 2.0%. This is to improve the properties of things.

The amount of Cr is limited for the purpose of obtaining a ferrite structure as well as the above-mentioned ferrite structure in combination with the amount of carbon from the viewpoint of corrosion resistance. That is, when the Cr content is 13% or less, the steel becomes martensitic. In the present invention, from this point of view and from the point of safety, the lower limit of Cr is set at 15%. On the other hand 2
If the coefficient exceeds 0, the steel tends to harden and there is a risk that workability may deteriorate. The limitation on the amount of S is related to the amount of Ce, and depending on the amount of Ce added, it will be desulfurized to various levels in the molten steel stage, and in the best case it will be desulfurized to around 0.001%.
When the feed amount of e is low, -hi rises to around 0.02 coefficient, so it is limited as described above.

Limiting the amount of Ce is the basis of the present invention; if it is less than 0.01%, all the S cannot be fixed as water-insoluble Ce-containing sulfide or Ce-containing oxysulfide, and if it exceeds 1.0%, it is not economical. undesirable from a financial point of view. Therefore, it was limited as described above. In addition, when adding Ce, the Ce content is 90
It is preferable to use a cerium alloy of % or more. Next, one or more of Ti, Nb, MO, and B of the second invention steel is added to produce a stainless steel plate with excellent workability by preventing beam tsging, and a stainless steel plate with the purpose of further improving corrosion resistance. This is an application of the principle of the first invention steel.

When one or more types of KB of Ti and Nb are added at the same time, welding is prevented, rust resistance is improved, and M
When O is added, corrosion resistance is further improved, and at the same time, rust resistance is also improved.

Therefore, the upper and lower limits of the amount of TltNbtMOIB added are selected from the most preferable ranges from the viewpoint of prevention of bulging and corrosion resistance.

Examples of the present invention will be described below.

The method for manufacturing the sample is as follows.

The reason why the sample was made into a hot-rolled sheet was to clarify the rusting state of inclusions. The samples were prepared using the usual melting method for stainless steel, and various SUS24 type stainless steel ingots or slabs containing cerium as the main ingredient and other ingredients were produced, and heated at a heating temperature of 1170°C.
After hr retention, hot rolling, annealing at 850°C for 3 hr, cooling, grinding both sides and sides, polishing at 4500~+1000, degreasing, washing, and drying, and then carrying out JIS Z237L salt water spray test. The area ratio of rust occurrence was measured.

The results are shown in Table 1. As is clear from the above results, the rust resistance of the present invention is extremely excellent and the practical effects are great.

Claims (1)

[Claims] 1 C: 0.001-0.10%, Si: 0.05-1
．． 0%, Mn: 0.1-2.0%, Cr: 15.0-2
0.0%, S: 0.001-0.02%, Ce: 0.0
A ferritic stainless steel with excellent rust resistance, characterized in that it contains 1 to 1.0%, with the remainder consisting of iron and unavoidable impurities. 2C: 0.001-0.10%, Si: 0.05-1
．． 0%, Mn: 0.1-2.0%, Cr: 15.0-2
0.0%, S: 0.001-0.2%, Ce::0.0
1 to 1.0%, and further contains one or more of Ti, Nb, Mo, and B, and 0.01 to 1.0% for Ti and Nb.
Excellent rust resistance characterized by containing 1.0% of Mo, 0.01 to 5.0% of Mo, 0.001 to 0.05% of B, and the remainder consisting of iron and inevitable impurities. Ferritic stainless steel.