JPS6250442A - Stainless steel for dinnerware - Google Patents

Abstract

PURPOSE:To provide an austenitic stainless steel for dinnerware which contains respectively prescribed ratios of C, Si, Mn, P, S, Cu, Ni, Cr, N, Al and O, does not contain inclusions consisting of Al2O3 simple substance and excels in cold rolling and surface finishing. CONSTITUTION:The titled stainless steel contains, by weight, 0.02-0.06% C, 1.0-2.0% Si, 1.0-2.0% Mn, <=0.04% P, 0.002-0.010% S, 1.0-2.5% Cu, 8.0-10.0% Ni, 18.0-20.0% Cr, <=0.030% N, <=0.005% Al and <=0.0050% O, consists the balance substantially Fe and has the following characteristics: This steel does not contain the inclusions consisting of Al2O3 simple substance. The stainless steel is slightly hard in the annealed state but has less work hardenability and is provided with the characteristics as the stainless steel for dinnerware including the excellent resistance to scale and the characteristic to prevent the generation of polishing flaws.

Description

[Detailed Description of the Invention] [Industrial Applications] The present invention relates to stainless steel for Western tableware, and in particular to austenitic stainless steel with excellent cold heading properties and surface finish. Used in the field of pottery.

[Conventional technology]

Traditionally, austenitic stainless steels used as Western tableware materials include 5US304 steel, which is called 18-8 stainless steel, SU33051M, which is called 18-12 stainless steel, or commonly known as Double Eighteen. Examples include 18Cr-18Ni steel.

The manufacturing process for Western-style tableware involves cold-rolling a base plate that has been punched into the shape of the product using cantilever rolls.

If the material is hard or has a large amount of work hardening, it will take many rolling passes to reduce the thickness to the specified thickness.
The former causes a strong impact between the material and the rolls, and the latter between the rolls, producing a strong impact sound and damaging the rolling mill.

It is punched after rolling, and the greater the hardening, the shorter the life of the punching tool. In addition, the head of a spoon is pressed into a dish shape during the extrusion process, but generally process annealing is performed in IIR. In this case, vacuum annealing furnaces or atmosphere furnaces are rarely used, and therefore, oxide scale is generated during annealing, increasing the number of steps in the subsequent polishing process, or the scale is embedded in the base metal during polishing and unnecessary polishing is required. In need of.

To reduce the hardening and work hardening of austenitic stainless steel, the Stainless Steel Handbook (Nikkan Kogyo Shimbunsha 1988)
Although it is basically effective to increase the amount of Nl in the steel as shown in page 358, line 23 (Published in 2010), this method is not economical because it uses a large amount of expensive N1. On the other hand, according to JP-A No. 55-91961, Cu lowers the strength and increases the ductility of austenitic stainless steel, similar to Ni, and the same tendency can be seen from the Vickers hardness-temperature relationship diagram of JP-A No. 56-261. I can see it.

Also, according to Japanese Patent Publication No. 51-29854, the composition of steel is S.
i: 0.5-2.5%, Cr: 15-19%, Mn
: 10-5.0%, Cu: 10-4.0%, Ni: 6
．． A great technique has been developed to improve stretchability and deep drawability by reducing the total amount of solute carbon and nitrogen to less than 0.004%. Similarly, as an austenitic stainless steel that provides deep drawability, JP-A-57-1
6152, an austenitic stainless steel to which Cu is added, has been proposed.

However, austenitic stainless steel used as a material for Western tableware differs from these so-called austenitic stainless steels for deep drawing in the following points. In other words, it is somewhat hard in the annealed state, the work hardening is smaller than that for deep drawing applications, it has good scale resistance during process annealing, and it is possible to control the shielding of nonmetallic inclusions, which is not a problem for deep drawing applications. At the same time, there are many differences such as the fact that a good surface finish cannot be obtained unless the absolute amount is reduced, and these demands for stainless steel for Western tableware are not fully satisfied at present.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an austenitic stainless steel with excellent cold rollability and surface finish in view of the current state of the stainless steel for Western tableware.

[Means and effects for solving the problems] The above objects of the present invention are achieved by the following two inventions. The gist of the first invention is as follows. That is, in terms of weight ratio, C:' 0.02-0.06%, Si: 10-2.0%
Mn: 10-2.0%, P: 0.04% or less S: 0.002-0.010%, Cu: 10-2
．． 5% Ni: 8. 0-10.0%, Cr: 1
8.0-20.0% N: 0.030% or less, Al: 0.
This stainless steel for Western tableware is characterized by containing 0:005% or less and 0:00050% or less, containing no inclusions consisting of simple Al2O3, and having the remainder substantially composed of Fe, and having excellent cold heading properties and surface finish.

The gist of the second invention is that the C1Si of the first invention,
In addition to the same basic components as Mn, P, S, Cu, Ni, Cr, N, Aj', 0, it further contains Mo: 0.20 to 15%, and the remainder does not contain inclusions consisting of Al2O alone. is a stainless steel for Western tableware that is essentially composed of Fe and is characterized by excellent cold rollability and surface finish.

The present inventors investigated finished spoons as products and discovered that, depending on the type of non-metallic inclusions in the steel, microscopic pit-like defects can be observed with the naked eye during polishing to a high finish, and these defects are the most important. After obtaining the knowledge that inclusions mainly composed of alumina are likely to occur, the present invention was completed as a result of further research.

The reason for limiting the component composition in the present invention is as follows.

C: C has the effect of influencing the hardness in the annealing state and working state, but if it is less than 0.020%, it tends to be softer, and if it is less than 0.020%, it tends to be softer.
If it exceeds 0.060%, the hardening of the processed state becomes particularly large, so it is limited to a range of 0.020 to 0.060%.

S1: Since Sl hardens the material in the annealed state, it is not desirable to contain it in large amounts as a material for Western tableware, but it does reduce the scale adhesion during process annealing (at the same time as scraping, it significantly lowers the amount of oxygen in the steel). (The amount necessary for rubbing was limited to a range of 1°0 to 260%.

Mn: Like Si, Mn is used as a deoxidizing agent and at the same time helps stabilize the austenite phase, so it must be present at least 10%
Although it is necessary, if it exceeds 2.0%, it impairs the scale resistance during process annealing and increases the hardness of the annealed steel more than necessary, so the lower limit was set to 10% and the upper limit was set to 20%.

P: If P exceeds 0.004%, it tends to damage the punched fracture surface, so the upper limit was set at 0.04%.

S: Since S impairs corrosion resistance, a lower value is preferable, but 0.
If it is less than 002%, the punching burr will be large, and 0006
If it exceeds 0002~00%, pitting corrosion is likely to occur.
It was limited to a range of 0.06%.

Cu: Like Ni, Cu suppresses work hardening and improves rollability, but if it is less than 10%, the effect is relatively small;
%, the effect is saturated and at the same time hot workability is impaired, so the content was limited to a range of 10 to 25%.

Ni: N1 reduces the hardness and work hardening in the annealed state, but 8
．． If it is less than 0%, the effect of reducing work hardening will be small even if the content of other components is controlled, and if it exceeds 10.0%, the austenite will be excessively stabilized and the bending strength of the handle will be reduced too much, and at the same time it will be expensive. Therefore, it was set in the range of 80 to 10.0%.

C": C" is added to ensure corrosion resistance, but if it is less than 180%, the corrosion resistance as an austenitic stainless steel cannot be maintained, and if it exceeds 200%, the loss of δ-ferrite in the cast structure is difficult to occur and 180~ to impair machinability.
It was limited to a range of 20.0%.

N: N helps stabilize the austenite phase, but at the same time it has the effect of increasing hardness and work hardening in the annealed state, so the content is 0.030%, which shows appropriate work hardening due to the synergistic effect with C. The range was as follows.

AI = Al is usually used as a deoxidizing agent, but Al2O3 as a deoxidizing product is hard and floats up without being polished during the Western tableware polishing process, which is the main cause of surface flaws. Since the inclusions are mixed into the raw material of the alloying element as impurities, the amount of inclusions generated from Al2O3 alone was limited to 0005% or less, which is the negligible limit.

O: 0 is preferably as small as possible in order to reduce inclusions and avoid surface flaws caused by inclusions on the finished surface of Western tableware, but even if fine Mn and Sii acid compound compounds are formed, surface flaws will not occur. The amount was limited to 0.0050% or less, which is an amount that hardly causes any problems.

The above C1Si, Mn, %P, S, Cu, Ni, Cr.

Although the basic composition of the present invention includes limited amounts of N, AI, and O, stainless steel for Western tableware that further contains MO in the following limited amounts has specific effects.

The reason for this limitation is as follows.

MO= Mo is an element effective in improving the pitting corrosion resistance of stainless steel. Western tableware may rust depending on the washing conditions.
Mo has the effect of preventing sanitary deterioration, but 02%
If the amount is less than 15%, there is no effect, and if the amount is more than 15%, the effect is saturated and it is uneconomical, so the amount is limited to 0.2 to 15%.

In the present invention, the amount of each component is limited as described above, the content of alloy components is comprehensively considered, the hardness in the annealed state is controlled within a certain hardness range, and furthermore, 60% cold heading is performed. By controlling the hardness after coating to a low range, the ease of processing Western tableware is improved, and at the same time, 81, Mn and A
Care was taken to specify the I content to avoid polishing pressure caused by nonmetallic inclusions.

〔Example〕

Various austenitic stainless steels whose components are shown in Table 1 are cast into 30 kg ingots by small-scale melting.
A 3I+In+ steel plate was obtained by known hot rolling, cold rolling and annealing. The grain size after these heat treatments is f degree number 7.
It was between 1 and 81.

The comparative steels are ordinary 5US304 steel and a known austenite-based stainless steel to which Cu is added.

The hardness, scale resistance, generation of polishing pressure, etc. of 3 mm steel plates in an annealed state and a 60% cold rolled state were investigated, and the results are shown in Table 2.

Table 2 Hardness Jf is Vickers hardness at a load of 10 kg on the plate surface.

The scale resistance was evaluated by the degree of scale adhesion when heated to 900°C with butane combustion as follows.

○ mark: Good (dark blue) Δ mark: Acceptable (red bean color) Perform bar polishing and check whether polishing pressure is generated. L: Not generated, X mark:
Indicated by occurrence.

As is clear from Table 2, the steel of the present invention has a moderate Hv of 30 to 1.
Since it has an initial hardness of 60 and a low processing hardness of 50 to 390 after 60% rolling, the handle, which is rarely cold-formed, will bend during use, and the head will bend when processing Western tableware. Able to smoothly handle part rolling, potting, part patterning, stamp marking, etc. Furthermore, the steel of the present invention is improved by adding Sl and Mn.
It can be seen that a relatively high degree of deoxidation is possible without using 1, and generation of polishing pressure can be prevented.

〔Effect of the invention〕

As is clear from the above examples, the present invention limits the components of the stainless steel for Western tableware, in particular limits A/ to 0005% or less, and comprehensively considers the alloy components.
It was possible to obtain a stainless steel that is somewhat hard in the annealed state, has low work hardening properties, has excellent scale resistance, and has the characteristics of a stainless steel for western tableware, which prevents the generation of polishing pressure.

Claims (2)

[Claims] (1) C: 0.02-0.06%, Si: 10-2.0% Mn in weight ratio
: 1.0-2.0%, P: 0.04% or less S: 0.00
2-0.010%, Cu: 1.0-2.5% Ni: 8.
0 to 10.0%, Cr: 18.0 to 20.0%, N: 0.
030% or less, Al: 0.005% or less O: 00050
% or less, does not contain inclusions consisting of single Al_2O_3, and the remainder consists essentially of Fe, and has excellent cold heading properties and surface finish. (2) C: 0.02-0.06%, Si: 1.0-2.0%M in weight ratio
n: 1.0-2.0%, P: 0.04% or less S: 0.0
02-0.010%, Cu: 1.0-2.5% Ni: 8
．． 0-10.0%, Cr:18.0-20.0%N:0
．． 030% or less, Al: 0.005% or less O: 0.00
50% or less, Mo: 0.2-1.5%, Al_2
Does not contain inclusions consisting of simple O_3, and the remainder is essentially Fe.
A stainless steel for Western tableware that is characterized by excellent cold heading properties and surface finish.