JP4256550B2

JP4256550B2 - Wear resistant steel for processing

Info

Publication number: JP4256550B2
Application number: JP36715399A
Authority: JP
Inventors: 建次郎伊東; 輝彦末次; 広森川; 隆山内
Original assignee: Nippon Steel Nisshin Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 1999-12-24
Filing date: 1999-12-24
Publication date: 2009-04-22
Anticipated expiration: 2019-12-24
Also published as: JP2001181799A

Description

【０００１】
【産業上の利用分野】
本発明は、アブレッシブな磨耗に曝される環境で使用され、加工性，耐摩耗性及び耐食性に優れた鋼に関する。
【０００２】
【従来の技術】
靴底との接触で磨耗する床材やエスカレータ部材，他の部品との摺動摩擦で磨耗する電気・電子機器部材等の広範な分野にわたり、耐摩耗性が要求される用途ではステンレス鋼等の高強度鋼材が使用されている。使用環境によっては，耐食性に優れていることも要求特性の一つである。
床材，エスカレータ部材，織機部材，電気・電子機器部材等の寿命は、使用環境によっても異なるが、材料がもつ耐摩耗性の如何に大きく影響される。そこで、耐摩耗性が要求される部材には，炭素含有鋼を焼入れして組織強化した材料や冷間加工等で強度を向上させた加工強化材等が使用されている。
【０００３】
【発明が解決しようとする課題】
磨耗は非常に複雑な機構をとる現象であることから，磨耗する部位での磨耗原因が明らかにされないまま、高強度材を用いて耐摩耗性の向上を図っているのが現状であり、実使用環境で実機に材料を装備させ，使用しながら材料寿命を評価している。そのため、材料選定に長時間を要することを始めとし、適正な材料選定に苦慮している。
また、エスカレータの階段用プレート材等のように、複雑な形状に塑性加工され且つ耐摩耗性及び耐食性が必要とされる用途ではプレス加工が容易なステンレス鋼が使用されているが、靴底等により磨耗で磨り減っていくのがよく見かけられる。更に、軸受等では、粉末成形された高価な耐磨耗材を使用する場合があるものの、或いは耐摩耗性を犠牲にして安価な材料で必要形状に加工した部材を使用し、磨耗に対しては頻繁な部品交換で対応している場合が多い。
【０００４】
【課題を解決するための手段】
本発明は、このような過酷な磨耗に曝される環境下で使用される部材に要求される耐摩耗性を改善すべく案出されたものであり、加工性に優れたオーステナイト相のマトリックスに硬質炭化物を分散析出させることにより、アブレッシブな磨耗に対しても十分な耐摩耗性を呈するスウェージ加工用耐磨耗鋼を提供することを目的とする。
本発明の加工用耐摩耗鋼は、その目的を達成するため、Ｃｒ：８〜３５質量％，Ｎｉ：６〜２０質量％，Ｃ：０．０５〜１．５０質量％，Ｓｉ：０．０２〜２．５質量％，Ｍｎ：０．０２〜３．０質量％，Ｔｉ，Ｎｂ，Ｚｒ，Ｗから選ばれた１種又は２種以上：０．０５〜３．０質量％，残部がＦｅ及び不可避的不純物の組成をもち、マトリックスに分散しているＴｉ，Ｎｂ，Ｚｒ及び／又はＷの炭化物が総量で０．１質量％以上に調整されていることを特徴とする。
【０００５】
【作用】
本発明者等は、摩耗損傷した部材や摩耗テストした対象物等を多数取り寄せ、摩耗損傷部位や対象物をミクロ的な観点から調査した。その結果、摩耗した部材の大半では、研削されたような疵が摩耗部分に観察された。また、摩耗損傷部材の周囲や対象物等には、アルミナ，炭化ケイ素等の硬質粒子の付着が検出された。研削されたような疵や硬質粒子の付着から、このときの摩耗現象は、硬質粒子が介在した摩耗であることが判った。なお、本明細書では、同材又は異材相互の接触面に硬質粒子が介在し、振動又は摺動過程で接触面が硬質粒子等で擦過・研削される摩耗をアブレッシブな摩耗という。
アブレッシブな摩耗は、種々の摩耗現象の中でも最も激しい摩耗であり、この摩耗に耐える材料の開発が望まれている。
【０００６】
耐摩耗性を向上させる方法として、ステンレス鋼をスウェージ加工して高強度化する方法を検討した。単にスウェージ加工で硬度を上昇させただけでは、図１に示すようにアブレッシブな摩耗量は若干低下するものの、顕著な摩耗抑制効果は発現せず、スエージ加工による加工強化では耐摩耗性を大幅に改善できないことが判った。冷間加工で加工硬化する場合、材料の成形加工が困難になり、必要部品が得られなくなる。
アブレッシブな摩耗に対する抵抗力が加工強化等で高められないことは、アルミナ，炭化ケイ素等の硬質粒子が非常に硬く、加工硬化等で得た硬さよりも硬いことに原因があるものと推察される。すなわち、加工硬化等で得た硬さは、アルミナ，炭化ケイ素等の硬質粒子の硬さに比較するとごく僅かであり、アブレッシブな摩耗を抑制する作用は少ないものと考えられる。
【０００７】
摩耗機構の解明及び摩耗に耐えうる材料の調査を重ねる過程で、鋼のマトリックスに硬質炭化物を所定量以上分散析出させると、耐摩耗性が飛躍的に向上することを見出した。具体的には、アルミナ，炭化ケイ素等の硬質粒子とほぼ同じ硬さをもつ炭化物としてＴｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗ等の炭化物に着目し、これら炭化物の析出量とアブレッシブな摩耗に対する耐摩耗性の関係を調査した。その結果、同じ硬さの素材であっても、Ｔｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗ等の炭化物を分散析出させるとアブレッシブな摩耗が抑制されることが判った。
【０００８】
本発明鋼は、耐食性を付与するために８〜３５質量％のＣｒ及び加工性を付与するために６〜２０質量％のＮｉを含んでいる。Ｃｒ含有量が８質量％を下回ると、Ｃｒ添加による防食効果が低減する。しかし、３５質量％を超える過剰量のＣｒが含まれると、熱間加工性が低下し、製造コストの上昇を招く。Ｎｉ含有量が６質量％未満では、良好な加工性を呈するオーステナイト相が生成されず、複雑な加工ができなくなる。オーステナイト相はＮｉ含有量の増量に応じて安定化するが、過剰のＮｉ含有は鋼材コストを上昇させる原因であることから、Ｎｉ含有量の上限を２０質量％に規定した。
【０００９】
オーステナイト相のマトリックスに総析出量で０．１質量％以上のＴｉ，Ｎｂ，Ｚｒ，Ｖ及び／又はＷの炭化物を析出させるため、Ｃ含有量を０．０５〜１．５０質量％に規制し、Ｔｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗの１種又は２種以上を０．０５〜３．０質量％添加する。Ｃは、炭化物として消費される他に、マトリックスの強度を向上させることにも有効な合金成分である。しかし、１．５０質量％を超える過剰量のＣは、鋼材の熱間加工性を低下させる。
【００１０】
炭化物総析出量０．１質量％以上は、後述する実施例でも説明しているように、耐摩耗性に及ぼす析出炭化物の影響調査から見出された臨界値であり、０．１質量％以上の総析出量を確保することにより炭化物のない鋼材に比較して格段に優れた耐摩耗性が得られる。Ｔｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗ等の添加量を０．０５質量％以上に設定するとき、マトリックスに分散析出した炭化物の総析出量が０．２質量％以上になる。しかし、Ｔｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗ等の成分は、溶製時の湯流れ性の低下，金属間化合物生成による靭性の低下，素材コストの上昇等のため、上限を３．０質量％に設定した。
【００１１】
本発明鋼は、他の合金成分としてＳｉを０．０２〜２．５質量％，Ｍｎを０．０２〜３．０質量％の範囲にすることが好ましい。
【００１２】
【実施例】
表１に示す各種鋼を常法に従って溶製し、インゴットに鋳造した。溶体化処理後、直径１５ｍｍの丸棒に熱間鍛造した。丸棒を１０５０度で溶体化処理し、直径１０ｍｍの丸棒に切削加工して供試材を得た。
【００１３】

【００１４】
供試材に分散析出した炭化物を定量分析すると共に、アブレッシブな磨耗に対する耐摩耗性及び耐食性を調査した。また、直径１０ｍｍの丸棒をスウェージング加工し、６０％以上のスウェージング加工が可能なものを○，６０％のスウェージング加工ができなかったものを×として加工性を評価した。
炭化物の析出量は、供試材を沃素アルコール溶液に浸漬し、超音波を加えて鋼材を溶解した後、液中に残った炭化物の残渣量から求めた。炭化物の形態は残渣のＸ線回折で同定し、個々の金属元素量は湿式分析及びガス分析で求めた。
【００１５】
アブレッシブな摩耗に対する耐摩耗性は、ピンオンディスク型の摩擦摩耗試験機を用いて調査した。接触面が直径５ｍｍの円柱状試験片をピンに取り付け、炭化ケイ素粉末を塗布した研磨紙をディスクに貼り付けた。ピン側の試験片に４０Ｎの負荷荷重Ｆ（Ｎ）を加え、回転しているディスクに摩擦速度０．７ｍ／秒で摩擦距離Ｌ＝０．５ｋｍを摺動させた後、試験片の摩耗量Ｗ（ｍｍ³）を測定した。測定値から次式に従って比摩耗量Ｃを算出した。比摩耗量Ｃで耐摩耗性を判定し、１．０×１０^-4ｍｍ²／Ｎ未満を○，１．０×１０^-4ｍｍ²／Ｎ以上を×と評価した。
比摩耗量Ｃ＝Ｗ／（Ｌ×Ｆ）×１０^-4
耐食性に関しては、５％塩水を７２時間噴霧する試験に供試材を供した後、試験片の表面を観察し、錆発生の有無を調査した。錆が検出されなかったものを○，錆が観察されたものを×として耐食性を評価した。
【００１６】
表２の調査結果にみられるように、炭化物が析出していない比較鋼８では１．３×１０^-4（ｍｍ²／Ｎ）以上の大きな被磨耗量Ｃが示されたが、炭化物が多量に析出するほど被磨耗量Ｃが小さくなった。そこで、被磨耗量Ｃと炭化物総析出量とをグラフ化したところ、両者の間に図２に示す関係が成立していた。すなわち、炭化物総析出量の増加に応じて被磨耗量Ｃが減少し，炭化物総析出量が０．１質量％以上になると被磨耗量Ｃが約１．０×１０^-4（ｍｍ²／Ｎ）未満になり、炭化物無析出の鋼材に比較して被磨耗量Ｃで８０％以下の優れた耐摩耗性を示すことが判った。
【００１７】
Ｃｒ含有量が８質量％未満の比較鋼１２では供試材表面に錆が観察されたが、８質量％以上のＣｒを含む比較鋼８〜１１及び本発明鋼１〜７では何れの供試材表面にも錆が検出されなかった。このことから、耐食性確保のためには８質量％以上のＣｒが必要であることが判る。
Ｎｉ含有量が６質量％未満の比較鋼１１，１２では安定したオーステナイト相が形成されておらず、６０％のスウェージ加工ができなかった。これに対し、Ｎｉ含有量が６質量％以上の比較鋼８〜１０及び本発明鋼１〜７では何れも供試材でも６０％以上のスウェージ加工が可能であった。このことから、スウェージによる加工性を確保するために、６質量％以上のＮｉが必要なことが確認される。また、本発明鋼１をスウェージ加工した後の被磨耗量Ｃは、図１に示すように炭化物析出のない試験番号８をスウェージ加工した場合に比較して格段に改善されていた。
【００１８】

【００１９】
【発明の効果】
以上に説明したように、本発明鋼は、アブレッシブな摩耗の原因であるアルミナ，炭化ケイ素等の硬質粒子とほぼ同じ硬さのＴｉ，Ｎｂ，Ｚｒ，Ｖ，Ｗ等の炭化物を総析出量０．1重量％以上の割合でオーステナイト相を含むマトリックスに分散析出させることにより、焼入れによる組織強化材や冷間加工等による加工強化材に比較して格段に優れた耐摩耗性及び加工性が付与されている。そのため、適度の加工が施されて使用される用途に適し、エスカレータのステップ材，エレベータ，厨房の床材，織機用機器，モータ軸受等の広範な分野で長寿命の部材として使用される。
【図面の簡単な説明】
【図１】スウェージ加工で高強度化した材料の硬さと被磨耗量との関係を示すグラフ
【図２】炭化物総析出量と被磨耗量との関係を示すグラフ[0001]
[Industrial application fields]
The present invention relates to a steel that is used in an environment exposed to abrasive wear and has excellent workability, wear resistance, and corrosion resistance.
[0002]
[Prior art]
In a wide range of fields, such as floor materials and escalator members that wear due to contact with the shoe sole, and electrical and electronic equipment members that wear due to sliding friction with other parts, stainless steel or other high High strength steel is used. Depending on the usage environment, excellent corrosion resistance is one of the required characteristics.
The lifetimes of floor materials, escalator members, loom members, electrical / electronic equipment members, etc. vary depending on the use environment, but are greatly affected by the wear resistance of the materials. For this reason, materials that require wear resistance include materials obtained by quenching carbon-containing steel and strengthening the structure, work strengthening materials that have been improved in strength by cold working, and the like.
[0003]
[Problems to be solved by the invention]
Since wear is a phenomenon that takes a very complicated mechanism, it is currently the case that the wear resistance is improved by using high-strength materials without revealing the cause of wear at the worn parts. The actual equipment is equipped with materials in the usage environment and the material life is evaluated while being used. For this reason, it is difficult to select an appropriate material, starting with the long time required for material selection.
In addition, stainless steel that is easy to press is used in applications that require plastic processing into complex shapes and require wear resistance and corrosion resistance, such as escalator stair plate materials. It is often seen that it is worn away by wear. In addition, in bearings, etc., powder-molded and expensive wear-resistant materials may be used, or parts that are processed into the required shape with inexpensive materials at the expense of wear resistance. In many cases, frequent parts are replaced.
[0004]
[Means for Solving the Problems]
The present invention has been devised to improve the wear resistance required for a member used in an environment exposed to such severe wear, and it is an austenite phase matrix having excellent workability. It is an object of the present invention to provide a wear-resistant steel for swaging that exhibits sufficient wear resistance against abrasive wear by dispersing and precipitating hard carbides.
In order to achieve the object, the wear-resistant steel for processing according to the present invention is Cr: 8-35% by mass, Ni: 6-20% by mass, C: 0.05-1.50% by mass, Si: 0.02 ~ 2.5% by mass, Mn: 0.02 to 3.0% by mass, one or more selected from Ti, Nb, Zr and W : 0.05 to 3.0% by mass, the balance being Fe and has a composition of unavoidable impurities, wherein the Ti dispersed in the matrix, Nb, carbides Z r 及 beauty / or W is adjusted to more than 0.1 mass% in total.
[0005]
[Action]
The present inventors ordered a large number of wear-damaged members and wear-tested objects, and investigated the wear-damaged sites and objects from a microscopic viewpoint. As a result, in most of the worn members, wrinkles that were ground were observed in the worn portions. Further, the adhesion of hard particles such as alumina and silicon carbide was detected around the wear damaged member and on the object. From the adhesion of wrinkles and hard particles that were ground, it was found that the wear phenomenon at this time was wear mediated by hard particles. In the present specification, wear in which hard particles are present on the contact surfaces of the same material or different materials and the contact surfaces are abraded or ground with hard particles or the like in the vibration or sliding process is referred to as abrasive wear.
Abrasive wear is the most severe of various wear phenomena, and the development of materials that can withstand this wear is desired.
[0006]
As a method of improving the wear resistance, a method of increasing the strength by swaging stainless steel was examined. If the hardness is simply increased by swaging, the amount of abrasive wear is slightly reduced as shown in Fig. 1, but no significant wear suppression effect is exhibited. It turned out that it cannot improve. When work hardening is performed by cold working, it becomes difficult to mold the material, and necessary parts cannot be obtained.
It is assumed that the resistance to abrasive wear cannot be increased by processing strengthening, etc., because hard particles such as alumina and silicon carbide are very hard and are harder than the hardness obtained by work hardening. . That is, the hardness obtained by work hardening or the like is very small compared to the hardness of hard particles such as alumina and silicon carbide, and it is considered that the effect of suppressing abrasive wear is small.
[0007]
In the process of elucidating the wear mechanism and investigating materials that can withstand wear, it has been found that wear resistance is dramatically improved by dispersing and precipitating a predetermined amount or more of hard carbide in a steel matrix. Specifically, focusing on carbides such as Ti, Nb, Zr, V, and W as carbides having almost the same hardness as hard particles such as alumina and silicon carbide, the amount of precipitation of these carbides and wear resistance against abrasive wear The sex relationship was investigated. As a result, it was found that even if the materials have the same hardness, abrasive wear is suppressed when carbides such as Ti, Nb, Zr, V, and W are dispersed and precipitated.
[0008]
The steel of the present invention contains 8 to 35% by mass of Cr for imparting corrosion resistance and 6 to 20% by mass of Ni for imparting workability. When the Cr content is less than 8% by mass, the anticorrosion effect due to the addition of Cr is reduced. However, when an excessive amount of Cr exceeding 35% by mass is included, the hot workability is lowered and the manufacturing cost is increased. When the Ni content is less than 6% by mass, an austenite phase exhibiting good workability is not generated, and complicated processing cannot be performed. The austenite phase is stabilized according to the increase in the Ni content, but excessive Ni content is a cause of increasing the steel material cost, so the upper limit of the Ni content is defined as 20% by mass.
[0009]
In order to precipitate 0.1% by mass or more of Ti, Nb, Zr, V and / or W carbides in the matrix of the austenite phase, the C content is regulated to 0.05 to 1.50% by mass. , Ti, Nb, Zr, V, W or one or more of 0.05 to 3.0 mass% is added. In addition to being consumed as carbides, C is an alloy component that is effective for improving the strength of the matrix. However, an excessive amount of C exceeding 1.50% by mass reduces the hot workability of the steel material.
[0010]
The total carbide precipitation amount of 0.1% by mass or more is a critical value found from the investigation of the effect of precipitated carbides on wear resistance, as described in the examples described later, and is 0.1% by mass or more. By ensuring the total amount of precipitation of the steel, it is possible to obtain much superior wear resistance compared to steel materials without carbides. When the addition amount of Ti, Nb, Zr, V, W, etc. is set to 0.05% by mass or more, the total precipitation amount of carbides dispersed and precipitated in the matrix becomes 0.2% by mass or more. However, components such as Ti, Nb, Zr, V, and W have an upper limit of 3.0 mass% due to a decrease in molten metal flow during melting, a decrease in toughness due to the formation of intermetallic compounds, an increase in material cost, and the like. Set to.
[0011]
The present invention steel is 0.02 to 2.5 wt% of S i and the other alloy components, it is preferable that the Mn in the range of 0.02 to 3.0 wt%.
[0012]
【Example】
Various steels shown in Table 1 were melted in accordance with a conventional method and cast into ingots. After the solution treatment, hot forging was performed on a round bar having a diameter of 15 mm. A round bar was subjected to a solution treatment at 1050 ° C. and cut into a round bar having a diameter of 10 mm to obtain a test material.
[0013]

[0014]
While quantitatively analyzing the carbides dispersed and deposited on the test material, the wear resistance and corrosion resistance against abrasive wear were investigated. In addition, a round bar having a diameter of 10 mm was subjected to a swaging process. A processability of 60% or more that could be swallowed was evaluated as ○, and a process that was not able to perform a 60% swaging process was evaluated as x.
The amount of carbide precipitation was determined from the amount of carbide residue remaining in the solution after the test material was immersed in an iodine alcohol solution and the steel was dissolved by applying ultrasonic waves. The form of carbide was identified by X-ray diffraction of the residue, and the amount of each metal element was determined by wet analysis and gas analysis.
[0015]
Abrasion resistance against abrasive wear was investigated using a pin-on-disk friction and wear tester. A cylindrical test piece having a diameter of 5 mm on the contact surface was attached to a pin, and abrasive paper coated with silicon carbide powder was attached to the disk. A load of F (N) of 40 N was applied to the test piece on the pin side, and the friction distance L = 0.5 km was slid on the rotating disk at a friction speed of 0.7 m / sec. W (mm ³ ) was measured. The specific wear amount C was calculated from the measured value according to the following formula. Determining wear resistance specific wear rate C, and less than ^{^{1.0 × 10 -4 mm 2 / N}} ○, was evaluated as × least ^{^{1.0 × 10 -4 mm 2 / N}} .
Specific wear amount C = W / (L × F) × 10 ⁻⁴
Regarding the corrosion resistance, the test material was subjected to a test in which 5% salt water was sprayed for 72 hours, and then the surface of the test piece was observed to investigate the presence or absence of rust. Corrosion resistance was evaluated with ◯ indicating that no rust was detected and × indicating that rust was observed.
[0016]
As can be seen from the survey results in Table 2, the comparative steel 8 with no carbide precipitated showed a large wear amount C of 1.3 × 10 ⁻⁴ (mm ² / N) or more, but a large amount of carbide was present. The amount of wear C became smaller as it was deposited on the surface. Therefore, when the wear amount C and the total carbide precipitation amount were graphed, the relationship shown in FIG. 2 was established between them. That is, the wear amount C decreases as the total carbide precipitation amount increases, and when the total carbide precipitation amount is 0.1 mass% or more, the wear amount C is about 1.0 × 10 ⁻⁴ (mm ² / N It was found that the wear amount C was 80% or less, which was superior to that of steel with no carbide precipitation.
[0017]
In the comparative steel 12 having a Cr content of less than 8% by mass, rust was observed on the surface of the test material. However, in any of the comparative steels 8 to 11 and the present invention steels 1 to 7 containing 8% by mass or more of Cr, any test was performed. No rust was detected on the material surface. From this, it can be seen that 8% by mass or more of Cr is necessary to ensure corrosion resistance.
In comparative steels 11 and 12 having a Ni content of less than 6% by mass, a stable austenite phase was not formed, and 60% swaging was not possible. In contrast, the comparative steels 8 to 10 and the inventive steels 1 to 7 having a Ni content of 6% by mass or more and the inventive steels 1 to 7 were capable of swaging 60% or more even with the test material. From this, it is confirmed that 6 mass% or more of Ni is necessary to ensure the workability by swaging. Further, the wear amount C after swaging the steel 1 of the present invention was remarkably improved as compared with the case where the test number 8 without carbide precipitation was swaged as shown in FIG.
[0018]

[0019]
【The invention's effect】
As described above, the steel of the present invention has a total precipitation amount of carbides such as Ti, Nb, Zr, V, and W having the same hardness as that of hard particles such as alumina and silicon carbide that cause abrasive wear. .Distribution and precipitation in a matrix containing austenite at a ratio of 1% by weight or more gives much more excellent wear resistance and workability compared to structure strengthening material by quenching and work strengthening material by cold working. Has been. Therefore, it is suitable for applications that are used after being moderately processed, and is used as a long-life member in a wide range of fields such as escalator step materials, elevators, kitchen floor materials, loom equipment, and motor bearings.
[Brief description of the drawings]
[Fig. 1] Graph showing the relationship between hardness and wear amount of material that has been strengthened by swaging [Fig. 2] Graph showing the relationship between total carbide precipitation and wear amount

Claims

Cr: 8-35 mass%, Ni: 6-20 mass%, C: 0.05-1.50 mass%, Si: 0.02-2.5 mass%, Mn: 0.02-3.0 mass% %, Ti, Nb, Zr , or W selected from one or more: 0.05 to 3.0% by mass, the balance of which is a composition of Fe and unavoidable impurities, Ti dispersed in a matrix, nb, Z r 及 beauty / or W of swaging a wear steel carbide is adjusted to more than 0.1 mass% in total.