JPH046783B2 - - Google Patents
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- Publication number
- JPH046783B2 JPH046783B2 JP21216887A JP21216887A JPH046783B2 JP H046783 B2 JPH046783 B2 JP H046783B2 JP 21216887 A JP21216887 A JP 21216887A JP 21216887 A JP21216887 A JP 21216887A JP H046783 B2 JPH046783 B2 JP H046783B2
- Authority
- JP
- Japan
- Prior art keywords
- corrosion resistance
- weight
- sample
- corrosion
- machinability
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- 238000005260 corrosion Methods 0.000 claims description 62
- 230000007797 corrosion Effects 0.000 claims description 62
- 239000010935 stainless steel Substances 0.000 claims description 13
- 229910001220 stainless steel Inorganic materials 0.000 claims description 13
- 229910018487 Ni—Cr Inorganic materials 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 10
- 238000010586 diagram Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910052797 bismuth Inorganic materials 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910052750 molybdenum Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 150000007513 acids Chemical class 0.000 description 3
- 238000009835 boiling Methods 0.000 description 3
- 238000005553 drilling Methods 0.000 description 3
- 239000004310 lactic acid Substances 0.000 description 3
- 235000014655 lactic acid Nutrition 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 229910000997 High-speed steel Inorganic materials 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 229910000915 Free machining steel Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- -1 TiC Chemical class 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Description
＜産業上の利用分野＞
この発明は、Ni−Cr系SUS304ステンレス鋼を
ベースとしてその耐食性と被削性を改善し、特に
食品用機器の材料として好ましく利用することが
できるNi−Cr系ステンレス鋼に関するものであ
る。
＜従来の技術＞
JISに定められたSUS304の化学成分は表１の
とおりである
<Industrial Application Field> The present invention is based on Ni-Cr stainless steel SUS304, which improves its corrosion resistance and machinability, and which can be particularly preferably used as a material for food equipment. It is related to. <Conventional technology> The chemical composition of SUS304 specified by JIS is as shown in Table 1.
【表】
SUS304は耐食性材料として広く用いられてい
るが、被削加工性が非常に悪い。快削性が要求さ
れる場合には、従来、耐食性を大幅に犠牲にして
意図的に硫化物系介在物（MnS）を生成させる
方法が一般的に採られている。MnSが被削性を
改善する例を第１図に示す。同図は高速度鋼
（SKH−51（φ4））によりドリル穴あけ加工をした
場合の工具寿命とＳ及びMn量との関係を示して
おり、実験に用いた試料の成分は表１の通りであ
る。これによると工具寿命はＳ量が増すと長くな
るが、Mn量にはほとんど影響されないことが分
かる。すなわち被削性はMnS量が多くなるにつ
れて向上するのである。しかしMnS量を多くす
ることは耐食性を大幅に悪くするため、耐食性を
特に重視する食品用機器の中で強腐食環境（例え
ば、塩化物環境や酸性飲料環境等）にも対応させ
るようにするには、さらにMnSの主成分である
鋼中のＳ及びMnの組成比Mn／Ｓ比を小さくし、
MnS中の固溶Cr量を多くすることが有効とされ
ている（「鉄と鋼」、70（1984）、P.741）。
Mn／Ｓ比を小さくすると耐食性が改善される
例を第２図で説明する。同図は３％の食塩水（30
℃）中でのMn／Ｓ比と孔食発生電位V′c100の関
係を示しており、実験に用いた試料の成分は表１
の通りである。これによるとMn／Ｓ比が小さい
試料ほどV′c100は貴となり、耐孔食性が優れて
いることがわかる。
このように従来は、Ni−Cr系ステンレス鋼に
おいて耐食性と被削性とを改善するには、MnS
を生成しMn／Ｓ比を低下させる方法が採られて
いた。
＜発明が解決しようとする問題点＞
しかしながら上記したMnSの生成およびMn／
Ｓ比を小さくすることをバランスよく調整するこ
とによつて、耐食性を損わず被削性を改善するこ
とはある程度可能であるが、未だ充分満足できる
ものではなかつた。
そこでこの発明は、SUS304をベースとして、
Cu、Mo、Biを一定量添加することで耐食性と被
削性の両方がさらに優れたNi−Cr系ステンレス
鋼を提供することを目的としてなされたものであ
る。
＜問題点を解決するための手段＞
この発明による耐食性および被削性を改善した
Ni−Cr系ステンレス鋼は、SUS304ステンレス鋼
を基本成分としてこれを一部変更した次のような
化学組成を有するものである：C0.08重量％以下、
Si1.0重量％以下、Mn0.7重量％以下、P0.04重量
％以下、S0.005重量％以下、Ni8.0〜12.0重量％、
Cr17.0〜20.0重量％、Mo0.40〜0.80重量％、
Cu0.10〜0.30重量％、Bi0.03〜0.12重量％、およ
び残部Fe。
＜作用＞
Biは被削性を改善する元素であつて、0.03重量
％以下では被削性改善効果が少なく、一方0.12重
量％以上では鍛造性を害し、さらには孔食を発生
し易くなり耐食性に悪影響を及ぼす。そのためこ
の発明においては0.03〜0.12重量％の範囲でBiを
使用するが、この範囲が工業的には最適である。
Cuは添加量が多すぎると耐有機酸腐食性を低
下させることがある。またCuの添加は非酸化性
酸に対する耐食性を増すが、この作用はMoとの
共存で顕著になる。したがつてその添加範囲を
0.10〜0.30重量％に定めれば、耐有機酸腐食性を
維持できるとともに、Mo添加の相乗効果にて、
種々の環境下での耐食性の向上に寄与できる。
Moの添加は一般に不働態域を拡げ耐食性を増
す。具体的には、酸、海水、中性塩化物溶液など
に対して耐食性の向上に寄与するが、0.40重量％
以下では耐食性に無効となる場合があり、また
0.80重量％以上では耐食性改善への効果が添加量
の割には少なくなり、さらにコスト高となるた
め、この発明における0.40〜0.80重量％が最適で
ある。
ＳおよびMnについては、前述したようにこれ
らの量を低減すると耐食性が改善されるが、反面
において被削加工性を低下させる。この発明にお
いてはＳを0.005重量％以下、Mnを0.7重量％以
下として耐食性を改善する一方、被削性の低下は
被削性を改善する元素であるBiを添加すること
によつて補うことができる。
Niはオーステナイト（γ）系ステンレス鋼の
基本元素で、γ相を安定にする。強度面では靭性
の改善に寄与する。耐食性に関してはFe、Crに
比較して電気化学的に貴であるため、活性態域で
の腐食を抑制する。また、中性塩化物溶液や非酸
化性酸による腐食に対して、顕著な抵抗性を与
え、かつ不働態を強化する。したがつてこの発明
では、Niを8.0〜12.0重量％添加している。
Crはステンレス鋼の基本成分で、酸化性環境
下においてステンレス鋼の不働態化に寄与する。
すなわち、ステンレス鋼の耐食性はこの不働態皮
膜によつて維持されるものであり、Crはステン
レス鋼にとつて必須の元素である。したがつてこ
の発明では、Crを17.0〜20.0重量％添加してい
る。
Ｃの値に関しては、JISにも規定されているよ
うに、材料の金属組織的安定性、機械的性質、耐
食性、製造コスト等の面から重要な意味がある。
すなわち、Ｃは強力なオーステナイト生成元素で
あり、侵入型に固溶して強度を増大させるために
固溶限界範囲内で多く添加する必要がある。しか
し、Ｃ量を過度に多くすると熱処理、溶接等の熱
的影響を受けた場合、Cr23C6、Cr7C3、NbC、
TiC等の炭化物を形成し、耐食性の低下につなが
る。特にCr炭化物が形成されるとマトリツクス
中のCr量を低減させ、耐食性を極端に低下させ
ることから、ある一定量以下に抑える必要があ
る。さらに、最も多く生産されているSUS304に
合わせてＣ量を決めた方が安価に製造できる点も
考慮して、Ｃ量は0.08重量％以下とする。
Siの値も、製造性、機械的性質、製造コスト等
の面で重要な意味がある。Si添加により引張強
さ、弾性限が増大し、また耐食性に関しても
SiO2皮膜を形成し、耐食性が向上する。一方、
Siは協力なフエライト生成元素であり、オーステ
ナイトを不安定にさせる。圧延工程においてもSi
が多いと割れを生じる等の問題がでてくる。こう
したことを考慮すると、Si量はJISで規定されて
いる1.0重量％以下に抑えることが？？種々の材
料特性、製造コストの両面から最良となる。
Ｐは有害な作用の多い元素である。Ｐが増加す
ると孔食感受性が増大し、さらにオーステナイト
の結晶粒界に偏析して粒界腐食の原因となる。ま
た応力腐食割れ性を害することかに極力少ない方
が良い。しかし、製鋼過程において極低Ｐ化する
ことは技術的にも難しい問題であり、コストも非
常に高くつく。こうした点を考慮すると、Ｐ量は
JISで規定されている0.04重量％以下とするのが
性能、コスト両面から最良となる。
＜実施例＞
表２の試料１〜４はそれぞれ４通りの鋼種につ
いての各化学組成を示しており、試料４は本発明
の実施例の組成である。そして[Table] SUS304 is widely used as a corrosion-resistant material, but its machinability is very poor. When free machinability is required, conventional methods have generally been adopted in which sulfide-based inclusions (MnS) are intentionally generated at the expense of significant corrosion resistance. Figure 1 shows an example of how MnS improves machinability. The figure shows the relationship between tool life and S and Mn content when drilling with high-speed steel (SKH-51 (φ4)). The composition of the sample used in the experiment is as shown in Table 1. be. This shows that the tool life increases as the S content increases, but it is hardly affected by the Mn content. In other words, machinability improves as the amount of MnS increases. However, increasing the amount of MnS significantly deteriorates corrosion resistance, so food equipment that places particular emphasis on corrosion resistance should be made to be compatible with highly corrosive environments (e.g., chloride environments, acidic beverage environments, etc.). Furthermore, the composition ratio Mn/S of S and Mn in the steel, which is the main component of MnS, is reduced,
It is said that increasing the amount of solid solution Cr in MnS is effective ("Tetsu to Hagane", 70 (1984), p. 741). An example in which corrosion resistance is improved by decreasing the Mn/S ratio will be explained with reference to FIG. The figure shows a 3% saline solution (30
Table 1 shows the relationship between the Mn/S ratio and the pitting corrosion potential V'c100 in
It is as follows. According to this, it can be seen that the smaller the Mn/S ratio of the sample, the more noble the V'c100, and the better the pitting corrosion resistance. Conventionally, in order to improve the corrosion resistance and machinability of Ni-Cr stainless steel, MnS
A method has been adopted in which the Mn/S ratio is lowered by generating Mn. <Problems to be solved by the invention> However, the above-mentioned generation of MnS and Mn/
Although it is possible to some extent to improve machinability without impairing corrosion resistance by adjusting the reduction of the S ratio in a well-balanced manner, this is not yet fully satisfactory. Therefore, this invention is based on SUS304,
This was done with the aim of providing a Ni-Cr stainless steel that has even better corrosion resistance and machinability by adding certain amounts of Cu, Mo, and Bi. <Means for solving the problems> This invention improves corrosion resistance and machinability.
Ni-Cr stainless steel is a basic component of SUS304 stainless steel with some modifications, and has the following chemical composition: C0.08% by weight or less,
Si 1.0% by weight or less, Mn 0.7% by weight or less, P 0.04% by weight or less, S 0.005% by weight or less, Ni 8.0 to 12.0% by weight,
Cr17.0~20.0wt%, Mo0.40~0.80wt%,
Cu 0.10-0.30 wt%, Bi 0.03-0.12 wt%, and balance Fe. <Function> Bi is an element that improves machinability, and if it is less than 0.03% by weight, it has little effect on improving machinability, while if it is more than 0.12% by weight, it impairs forgeability, and it also tends to cause pitting corrosion, resulting in poor corrosion resistance. have a negative impact on Therefore, in this invention, Bi is used in a range of 0.03 to 0.12% by weight, and this range is industrially optimum. If the amount of Cu added is too large, the organic acid corrosion resistance may be reduced. Additionally, the addition of Cu increases the corrosion resistance against non-oxidizing acids, but this effect becomes more pronounced when it coexists with Mo. Therefore, the range of addition
If it is set at 0.10 to 0.30% by weight, organic acid corrosion resistance can be maintained, and the synergistic effect of Mo addition
It can contribute to improving corrosion resistance under various environments. Addition of Mo generally expands the passive region and increases corrosion resistance. Specifically, it contributes to improved corrosion resistance against acids, seawater, neutral chloride solutions, etc., but 0.40% by weight
Corrosion resistance may be ineffective if
If the content is 0.80% by weight or more, the effect on improving corrosion resistance will be small relative to the amount added, and the cost will increase, so 0.40 to 0.80% by weight is optimal in this invention. Regarding S and Mn, as described above, reducing these amounts improves corrosion resistance, but on the other hand, machinability is reduced. In this invention, corrosion resistance is improved by setting S to 0.005% by weight or less and Mn to 0.7% by weight, while reducing machinability can be compensated for by adding Bi, an element that improves machinability. can. Ni is the basic element of austenitic (γ) stainless steel and stabilizes the γ phase. In terms of strength, it contributes to improving toughness. Regarding corrosion resistance, it is electrochemically more noble than Fe and Cr, so it suppresses corrosion in the active state region. It also provides significant resistance to corrosion by neutral chloride solutions and non-oxidizing acids, and enhances passivity. Therefore, in this invention, 8.0 to 12.0% by weight of Ni is added. Cr is a basic component of stainless steel and contributes to passivation of stainless steel in oxidizing environments.
That is, the corrosion resistance of stainless steel is maintained by this passive film, and Cr is an essential element for stainless steel. Therefore, in this invention, 17.0 to 20.0% by weight of Cr is added. Regarding the value of C, as specified in JIS, it has an important meaning from the viewpoints of metallographic stability, mechanical properties, corrosion resistance, manufacturing cost, etc. of the material.
That is, C is a strong austenite-forming element, and in order to increase the strength by interstitial solid solution, it is necessary to add a large amount within the solid solubility limit range. However, if the amount of C is excessively increased, and when subjected to thermal effects such as heat treatment or welding, Cr 23 C 6 , Cr 7 C 3 , NbC,
Forms carbides such as TiC, leading to decreased corrosion resistance. In particular, when Cr carbide is formed, the amount of Cr in the matrix is reduced and the corrosion resistance is extremely deteriorated, so it is necessary to keep the amount below a certain level. Furthermore, considering the fact that it can be manufactured at a lower cost if the C content is determined according to SUS304, which is the most commonly produced material, the C content is set to 0.08% by weight or less. The value of Si also has important meaning in terms of manufacturability, mechanical properties, manufacturing cost, etc. The addition of Si increases tensile strength and elastic limit, and also improves corrosion resistance.
Forms a SiO 2 film, improving corrosion resistance. on the other hand,
Si is a cooperative ferrite-forming element and destabilizes austenite. Si is also used in the rolling process.
If there is too much, problems such as cracking will occur. Taking these things into consideration, is it possible to keep the Si content below 1.0% by weight as stipulated by JIS? ? It is the best in terms of both material properties and manufacturing costs. P is an element that has many harmful effects. As P increases, susceptibility to pitting corrosion increases, and P also segregates at grain boundaries of austenite, causing intergranular corrosion. Also, it is better to minimize the amount of stress as it may impair stress corrosion cracking properties. However, achieving extremely low P in the steel manufacturing process is technically difficult and extremely costly. Considering these points, the amount of P is
It is best from both performance and cost standpoints to keep the amount below 0.04% by weight as stipulated by JIS. <Example> Samples 1 to 4 in Table 2 show respective chemical compositions for four types of steel, and sample 4 has a composition of an example of the present invention. and
【表】
試料１〜試料３は試料４と耐食性及び被削性に
ついて比較するために調整した鋼種で、試料１は
SUS303系でBiを含有しておらず、試料２は
SUS304系でMo、Cu、Biを含有しておらず、ま
た試料３はMo、Cu、Bi含有のSUS304系である
が、本発明の組成範囲外にある。
(1) 耐全面腐食性の改善
第３図は試料１〜４の希硫酸（５％、沸騰）
中での腐食速度を示しており、本発明にかかわ
る試料４は他の３つの試料と比べて腐食速度が
小さく、耐食性が著しく向上している。特に
Mo、Cu、Biを含有した試料３は試料４と比べ
てすこぶる大きな腐食速度を示しており、この
ことは単にMo、Cu、Biを添加するだけではな
く、各化学成分を本発明のごとく調整すること
の重要性を示している。
第４図は試料１〜４の希硫酸（５％硫酸、30
℃）中でのアノード分極曲線である。図中〜
にて示す試料１から試料４までの各不働態化
限界電流密度（icrit）の大きさは＜＜＜
にて示す関係にあり、試料４の場合が最も小
さい。したがつて本発明にかかわる試料４は活
性態電位域での溶解抵抗が最も大きいために耐
食性が最も良い。
第５図は試料１〜４の希塩酸（0.05、0.1、
0.2、0.5％の各塩酸、沸騰）中での腐食速度を
示しており、本発明にかかわる試料４は0.5％
塩酸中の場合でのみ腐食が認められる。これに
対してSUS304系でも試料２、３は0.1％塩酸中
でも腐食しており、本発明による化学組成の範
囲は耐食性の面で非常に有効である。
第６図は試料１〜４の乳酸（50％乳酸、沸
騰）中での腐食速度を示す。傾向が第３図の硫
酸中での腐食の場合と類似しているが、ここで
も本発明にかかわる試料４の腐食速度は他の３
つの試料と比べて著しく小さいことが分かる。
以上のデータから、耐全面腐食性において本
発明にかかわる試料４は、優れた耐食性を有し
ていることが明らかである。
(2) 耐孔食性の改善
第７図は、試料１〜４の食塩溶液（３％食
塩、30℃）中における孔食発生電位（V′c100）
を測定した結果である。一般にこの値の高い方
が、孔食を発生しにくいことを意味する。本発
明にかかわる試料４は平均値で0.335Vであり、
他の３つの試料は全て0.3V以下である。これ
により試料４が最も耐孔食性に優れていること
が分かる。
(3) 被削性の改善
第８図は、試料１〜４に対して高速度鋼
（SKH−51（φ4））によりドリル穴あけ加工をし
た場合の工具寿命を示している。Biを添加し
た試料３、４に対する工具寿命は、Bi無添加
の試料２に対する工具寿命の３倍もあり、快削
性元素Biを添加すると、無添加の場合と比べ
て著しく被削性が改善されることが分かる。し
かも本発明にかかわる試料４は、快削鋼の
SUS303系の試料１と比べても工具寿命に大差
がなく、試料４は耐食性に加えて被削性をも改
善されている。
＜発明の効果＞
以上の説明からわかるようにこの発明のステン
レス鋼は、SUS304ステンレス鋼の耐食性と被削
性の両方を大幅に改善でき、耐食性を重視する食
品用機器の材料として特に好ましく使用できるも
のである。[Table] Samples 1 to 3 are steel types adjusted for comparison with sample 4 in terms of corrosion resistance and machinability.
Sample 2 is SUS303-based and does not contain Bi.
Sample 3 is a SUS304 series that does not contain Mo, Cu, and Bi, and Sample 3 is a SUS304 series that contains Mo, Cu, and Bi, but is outside the composition range of the present invention. (1) Improvement of general corrosion resistance Figure 3 shows samples 1 to 4 of dilute sulfuric acid (5%, boiling)
Sample 4 according to the present invention has a lower corrosion rate and significantly improved corrosion resistance than the other three samples. especially
Sample 3 containing Mo, Cu, and Bi shows a significantly higher corrosion rate than Sample 4. It shows the importance of doing things. Figure 4 shows samples 1 to 4 of dilute sulfuric acid (5% sulfuric acid, 30%
℃) is the anodic polarization curve. In the diagram~
The magnitude of each passivation critical current density (icrit) from Sample 1 to Sample 4 shown in is <<<
There is a relationship shown in , and the case of sample 4 is the smallest. Therefore, sample 4 according to the present invention has the highest resistance to dissolution in the active potential region, and therefore has the best corrosion resistance. Figure 5 shows samples 1 to 4 of dilute hydrochloric acid (0.05, 0.1,
It shows the corrosion rate in 0.2% and 0.5% hydrochloric acid (boiling), and sample 4 related to the present invention has 0.5% hydrochloric acid.
Corrosion is observed only in hydrochloric acid. On the other hand, samples 2 and 3 of the SUS304 series were corroded even in 0.1% hydrochloric acid, and the chemical composition range according to the present invention is very effective in terms of corrosion resistance. FIG. 6 shows the corrosion rates of samples 1 to 4 in lactic acid (50% lactic acid, boiling). The tendency is similar to that in the case of corrosion in sulfuric acid in Figure 3, but here again the corrosion rate of sample 4 related to the present invention is higher than that of the other three.
It can be seen that it is significantly smaller than the other samples. From the above data, it is clear that Sample 4 according to the present invention has excellent general corrosion resistance. (2) Improvement of pitting corrosion resistance Figure 7 shows the pitting corrosion occurrence potential (V′c100) of samples 1 to 4 in a salt solution (3% salt, 30°C).
This is the result of measuring. Generally, a higher value means that pitting corrosion is less likely to occur. Sample 4 related to the present invention has an average value of 0.335V,
All other three samples are below 0.3V. This shows that sample 4 has the best pitting corrosion resistance. (3) Improvement of machinability Figure 8 shows the tool life when drilling holes in samples 1 to 4 using high speed steel (SKH-51 (φ4)). The tool life for samples 3 and 4 with Bi added was three times that of sample 2 without Bi added, and the addition of the free-machining element Bi significantly improved machinability compared to the case without addition. I know it will happen. Moreover, sample 4 related to the present invention is made of free-cutting steel.
There is no significant difference in tool life compared to SUS303-based sample 1, and sample 4 has improved machinability in addition to corrosion resistance. <Effects of the Invention> As can be seen from the above explanation, the stainless steel of the present invention can significantly improve both the corrosion resistance and machinability of SUS304 stainless steel, and can be particularly preferably used as a material for food equipment where corrosion resistance is important. It is something.
第１図は穴あけ加工による工具寿命とＳ及び
Mn量との関係図、第２図は食塩水中における
Mn／Ｓ比と孔食発生電位との関係図、第３図は
希硫酸中における試料１〜４と腐食速度との関係
図、第４図は希硫酸中における試料１〜４のアノ
ード分極特性図、第５図は希塩酸中における試料
１〜４と腐食速度との関係図、第６図は乳酸中に
おける試料１〜４と腐食速度との関係図、第７図
は食塩溶液中における試料１〜４と孔食発生電位
との関係図、第８図は穴あけ加工による工具寿命
と試料１〜４との関係図である。
Figure 1 shows the tool life and S and
The relationship diagram with the amount of Mn, Figure 2 is in saline solution.
A diagram of the relationship between Mn/S ratio and pitting corrosion potential. Figure 3 is a diagram of the relationship between samples 1 to 4 in dilute sulfuric acid and corrosion rate. Figure 4 is an anode polarization characteristic of samples 1 to 4 in dilute sulfuric acid. Figure 5 is a diagram of the relationship between samples 1 to 4 in dilute hydrochloric acid and the corrosion rate, Figure 6 is a diagram of the relationship between samples 1 to 4 in lactic acid and the corrosion rate, and Figure 7 is a diagram of the relationship between sample 1 and the corrosion rate in saline solution. Figure 8 is a diagram showing the relationship between tool life during drilling and samples 1 to 4.
Claims (1)
重量％以下、P0.04重量％以下、S0.005重量％以
下、Ni8.0〜12.0重量％、Cr17.0〜20.0重量％、
Mo0.40〜0.80重量％、Cu0.10〜0.30重量％、
Bi0.03〜0.12重量％、および残部がFeからなるこ
とを特徴とする耐食性および被削性を改善した
Ni−Cr系ステンレス鋼。1 C0.08wt% or less, Si1.0wt% or less, Mn0.7
Weight% or less, P0.04 weight% or less, S0.005 weight% or less, Ni8.0~12.0 weight%, Cr17.0~20.0 weight%,
Mo0.40~0.80wt%, Cu0.10~0.30wt%,
Improved corrosion resistance and machinability, characterized by Bi 0.03~0.12% by weight and the balance consisting of Fe.
Ni-Cr stainless steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21216887A JPS6455362A (en) | 1987-08-25 | 1987-08-25 | Ni-cr stainless steel improved in corrosion resistance and machinability |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21216887A JPS6455362A (en) | 1987-08-25 | 1987-08-25 | Ni-cr stainless steel improved in corrosion resistance and machinability |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6455362A JPS6455362A (en) | 1989-03-02 |
| JPH046783B2 true JPH046783B2 (en) | 1992-02-06 |
Family
ID=16618031
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21216887A Granted JPS6455362A (en) | 1987-08-25 | 1987-08-25 | Ni-cr stainless steel improved in corrosion resistance and machinability |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6455362A (en) |
-
1987
- 1987-08-25 JP JP21216887A patent/JPS6455362A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6455362A (en) | 1989-03-02 |
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