【発明の詳細な説明】[Detailed description of the invention]
本発明は、TIGアークによる金属部材の再溶融
表面硬化処理法に係り、更に詳細には比較的熱容
量の小さい金属部材に対し適用されるに適した再
溶融表面硬化処理法に係る。
TIGアークの如き高エネルギ密度源を用いた再
溶融表面硬化処理法は金属部材の表面を局部的に
硬化させる処理法として、種々の技術分野に於て
広く利用されている。例えばTIGアークにより金
属部材の表面をある範囲に亙つて硬化させること
は、従来より一般に、溶接トーチをウイービング
させたり、そのシングルビードを重ねつつその金
属部材の表面部を溶融させ、急冷することにより
行なわれている。
しかしこれらの方法による場合には、金属部材
の既に再溶融され硬化された部分がその近傍を通
過するTIGアークにより再加熱されるのでその部
位の硬度が低下し、またビードの重ね合わせられ
た部位の組織が不均一となることにより、その部
位に於ける耐摩耗性が必ずしも充分には向上しな
いという問題がある。また上述の如きウイービン
グ法などによる場合に於ては、そのビード端部に
於て充分な溶融を行なわせるタイミングが処理技
術上の問題となり、ビード端部に割れやブローホ
ール等の欠陥が生じ易いという問題がある。
かかるウイービング法などによる表面硬化熱処
理に於ける不具合に鑑み、特に熱容量の小さい金
属部材の再溶融表面硬化処理法として、アークス
ポツト溶接と同様の要領にて、表面硬化処理され
るべき金属部材に対し溶接トーチを静止状態に維
持し、その表面硬化処理されるべき表面をスポツ
ト状に溶融させる方法が考えられる。しかしこの
方法に於ては、金属部材の溶接トーチ直下の部分
が極端に深く溶融されその周囲の部分は充分には
溶融されないため、溶接トーチ直下の部分の周囲
の表面部をも溶融させ硬化させようとすれば、通
電電流を高くするか、又は金属部材の表面を幾つ
かの点に亙つて処理しなければならない。この場
合通電電流を高くすると、金属部材への入熱が過
大になり、生成されるチル層の結晶が粗大化し、
金属部材のその表面に於ける硬度や耐摩耗性は充
分には向上しない。また金属部材の表面を幾つか
の点に亙つて処理する場合には、処理能率が悪く
なるのみならず、上述のウイービング法の場合と
同様の不具合を生じる。
本願発明者等は上述の如き従来の再溶融表面硬
化処理法に於ける種々の不具合に鑑み、幾つかの
実験的研究を行なつた結果、ピーク電流時間がベ
ース電流時間以上になるよう連続的なTIGアーク
をパルス発振させることにより、TIGアークを金
属部材に対し走査しなくても部材表面の比較的広
い範囲を再溶融表面硬化処理し得ることを見出し
た。
本発明は、本願発明者等が行つた実験的研究の
結果得られた上述の如き知見に基き、TIGアーク
を金属部材に対し走査することなく部材表面を比
較的広い範囲に亙り均一に且迅速に硬化させるこ
とができるよう改善された再溶融表面硬化処理法
を提供することを目的としている。
かかる目的は、本発明によれば、連続的なTIG
アークを金属部材に対し静止状態に維持し、ピー
ク電流時間がベース電流時間以上になるようTIG
アークをパルス発振させることを特徴とするTIG
アークによる金属部材の再溶融表面硬化処理法に
よつて達成される。
かかる本発明による再溶融表面硬化処理法によ
れば、TIGアークのピーク電流により金属部材の
表面に溶融池が形成され、その溶融金属が一種の
遮熱スクリーンとして作用するので、TIGアーク
のベース電流によつて金属部材に与えられた熱が
金属部材の深さ方向よりもむしろその表面に沿つ
て周囲の部位へ伝達される。従つてTIGアークを
金属部材に対し走査させなくても、金属部材の表
面を比較的広い範囲に亙り比較的一様な深さに溶
融させることができるので、金属部材の表面を比
較的広い範囲に亙つて一様に且迅速に硬化させる
ことができ、これにより連続的で一様なTIGアー
クや断続的なTIGアークが使用されアークが走査
される場合に比して、処理能率を大幅に向上させ
ると共に、処理コストを大幅に低減することがで
き、また処理装置も簡便な構造のものであつてよ
い。またTIGアークが金属部材に対し走査される
上述の如き従来の再溶融表面硬化処理法に比し
て、表面硬化処理されるべき金属部材の表面の縁
部まで溶融する場合に於ても、その縁部部に生じ
る肩ダレは非常に小さく、その抑制制御も容易で
あり、また表面硬化処理後に於ける形状修正等の
後処理を簡便に行なうことができる。
尚、本発明による再溶融表面硬化処理法に於て
は、被処理材の材質や熱容量などによつて異なる
が、電圧12〜30V、ピーク電流120〜350A、ピー
ク電流時間0.05〜0.4秒、ベース電流10〜50A、ベ
ース電流時間0.05〜0.4秒の直流パルス電流が0.5
〜３秒程度通電されることが好ましい。
以下に添付の図を参照しつつ、本発明を実施例
について詳細に説明する。
実施例 １
第１図に示されている如く、自動車用デイーゼ
ルエンジンに組込まれるロツカーアーム１のカム
シヤフトのカムとの摺動面２（11×12mm）を下記
の表に示す処理条件にてTIGアークによる再溶融
表面硬化処理（Ａ及びＢ）を行ない、4000c.c.４サ
イクルデイーゼルエンジンに組込み、それぞれの
摩耗量を調べる摩耗試験を行なつた。また比較の
目的で、従来のウイービング法による処理Ｃおよ
びアークスポツトによる処理Ｄを行なわれたロツ
カーアームについても同様の摩耗試験を行なつ
た。
尚、被処理材としてのロツカーアームは球状黒
鉛鋳鉄（JIS規格FCD70）よりなり、重量は80ｇ
であつた。また各処理は図には示されていない
TIGトーチを摺動面２の中心３の上方に静止させ
た状態にて行なわれた。
The present invention relates to a remelting surface hardening treatment method for metal members using TIG arc, and more particularly to a remelting surface hardening treatment method suitable for application to metal members having a relatively small heat capacity. A remelting surface hardening treatment method using a high energy density source such as a TIG arc is widely used in various technical fields as a treatment method for locally hardening the surface of a metal member. For example, hardening the surface of a metal member over a certain range using a TIG arc has conventionally been done by weaving a welding torch, or by overlapping single beads to melt the surface of the metal member and rapidly cool it. It is being done. However, when these methods are used, the part of the metal component that has already been remelted and hardened is reheated by the TIG arc passing nearby, which reduces the hardness of that part, and also reduces the hardness of the part where the beads overlap. There is a problem that due to non-uniformity of the structure, the wear resistance in that area is not necessarily sufficiently improved. In addition, when using the weaving method as described above, the timing to ensure sufficient melting at the bead end becomes a problem in processing technology, and defects such as cracks and blowholes are likely to occur at the bead end. There is a problem. In view of the problems in surface hardening heat treatment by such weaving method, etc., as a re-melting surface hardening treatment method for metal parts with particularly small heat capacity, a method similar to arc spot welding is used for metal parts to be surface hardened. A possible method is to keep the welding torch stationary and melt the surface to be hardened in spots. However, in this method, the part of the metal part directly under the welding torch is melted extremely deeply and the surrounding part is not sufficiently melted, so the surface area around the part directly under the welding torch is also melted and hardened. If this is to be done, the current must be increased or the surface of the metal member must be treated at several points. In this case, if the applied current is increased, the heat input to the metal member becomes excessive, and the crystals of the generated chill layer become coarse.
The hardness and wear resistance of the surface of the metal member are not sufficiently improved. Furthermore, when the surface of a metal member is treated at several points, not only the treatment efficiency deteriorates, but also problems similar to those of the above-mentioned weaving method occur. In view of the various defects in the conventional remelting surface hardening treatment method as described above, the inventors of the present application conducted several experimental studies, and as a result, they found that the peak current time is continuous so that the peak current time is longer than the base current time. We have discovered that by oscillating a TIG arc in pulses, it is possible to remelt and harden a relatively wide area of the surface of a metal member without scanning the TIG arc over the metal member. The present invention is based on the above-mentioned knowledge obtained as a result of experimental research conducted by the inventors of the present invention, and is based on the above-mentioned findings obtained as a result of experimental research conducted by the inventors of the present invention. It is an object of the present invention to provide an improved remelting surface hardening treatment method that enables hardening of the surface of the surface. Such purpose, according to the invention, is achieved by continuous TIG
TIG the arc so that it remains stationary relative to the metal member and the peak current time is greater than or equal to the base current time.
TIG is characterized by pulse oscillation of the arc.
This is achieved by a remelting surface hardening process of metal parts using an arc. According to the remelting surface hardening treatment method according to the present invention, a molten pool is formed on the surface of the metal member due to the peak current of the TIG arc, and the molten metal acts as a kind of heat shielding screen, so that the base current of the TIG arc is reduced. The heat applied to the metal member by the metal member is transmitted to the surrounding parts along the surface of the metal member rather than in the depth direction of the metal member. Therefore, even if the TIG arc does not scan the metal member, it is possible to melt the surface of the metal member over a relatively wide range to a relatively uniform depth. The process can be cured uniformly and quickly over the entire area, significantly increasing processing efficiency compared to when a continuous, uniform TIG arc or an intermittent TIG arc is used and the arc is scanned. In addition, the processing cost can be significantly reduced, and the processing apparatus may have a simple structure. Furthermore, compared to the conventional re-melting surface hardening treatment method described above in which the TIG arc is scanned over the metal member, even when the edge of the surface of the metal member to be surface hardened is melted. Shoulder sagging occurring at the edge portions is very small and can be easily suppressed and controlled, and post-processing such as shape correction after surface hardening treatment can be easily performed. In addition, in the remelting surface hardening treatment method according to the present invention, the voltage is 12 to 30 V, the peak current is 120 to 350 A, the peak current time is 0.05 to 0.4 seconds, and the base temperature is Current 10~50A, base current time 0.05~0.4 seconds DC pulse current 0.5
It is preferable that the current be applied for about 3 seconds. DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures. Example 1 As shown in Fig. 1, the sliding surface 2 (11 x 12 mm) of the cam of the camshaft of the Rotsuker arm 1 incorporated in an automobile diesel engine was treated by TIG arc under the treatment conditions shown in the table below. A remelting surface hardening treatment (A and B) was performed, and the product was installed in a 4000 c.c. 4-cycle diesel engine, and a wear test was conducted to determine the amount of wear. For comparison purposes, similar wear tests were also conducted on rocker arms that had been subjected to treatment C using the conventional weaving method and treatment D using arc spotting. The Rotsuker arm, which is the material to be treated, is made of spheroidal graphite cast iron (JIS standard FCD70) and weighs 80g.
It was hot. Also, each process is not shown in the figure.
The test was carried out with the TIG torch stationary above the center 3 of the sliding surface 2.
【表】
試験の結果、従来のウイービング法による処理
Ｃに於ては、ロツカーアームの摺動面全体を処理
するのに長時間（６秒）を要し、またウイービン
グビードの重なり部分の摩耗量が他の部位に比し
て大きく、従つて処理後の摺動面の硬度及び耐摩
耗性が不均一であることが認められた。また従来
のアークスポツトによる処理Ｄの場合には、TIG
アーク直下の部分の溶け込みが極端に深く、その
周囲の部分をも溶融させるのに比較的長時間（４
秒）を要し、その結果としてTIGアークを直接受
けた部分のチル層の組織が粗大化しており、また
その摩耗量も他の部位に比して著しく大きいこと
が認められた。
これに対し本発明に従つて処理（Ａ及びＢ）さ
れたロツカーアームの摺動面は、上述の処理Ｃ及
びＤによるロツカーアームよりも硬度及び耐摩耗
性が優れており、また再溶融層の深さも一様であ
ることが認められた。第２図は特に処理Ａを施さ
れたロツカーアームのその長手方向に垂直な方向
の断面を6.2倍にて示す写真である。この第２図
からも解る如く、上述の処理Ａによれば、短時間
にて摺動面の実質的に全ての領域が一様に再溶融
され、一様に硬化されることが解る。
実施例 ２
実施例１の場合と同様、自動車用デイーゼルエ
ンジンに組込まれる排気バルブのバルブステムの
頂面を再溶融し硬化する処理を行なつた。尚採用
された処理条件は電圧18V、ピーク電流Ip＝
120A、ベース電流Ib＝20A、ピーク電流時間Tp
＝0.1秒、ベース電流時間Tb＝0.1秒、処理時間１
秒であり、被処理材としての排気バルブは耐熱鋼
（JIS規格SUH3）よりなる重量105ｇのものであ
つた。
処理後その断面の組織を観察したところ、バル
ブステムの頂面の実質的に全体に亙つて非常に微
細なマルテンサイト組織が形成されていることが
認められた。
以上の説明より本発明による金属部材の再溶融
表面硬化処理法によれば、被処理材の比較的広い
領域を迅速且一様に硬化させることができること
が理解されよう。
以上に於ては本発明を特定の実施例について詳
細に説明したが、本発明はこれらの実施例に限定
されるものではなく、本発明の範囲内にて種々の
実施例が可能であることは当業者にとつて明らか
であろう。[Table] The test results showed that in Process C using the conventional weaving method, it took a long time (6 seconds) to process the entire sliding surface of the Rotsuker arm, and the amount of wear at the overlapping part of the weaving bead was small. It was found that the hardness and abrasion resistance of the sliding surface after treatment were non-uniform as it was larger than other parts. In addition, in the case of treatment D using the conventional arc spot, TIG
The melting area directly under the arc is extremely deep, and it takes a relatively long time (4
As a result, the structure of the chill layer in the area directly exposed to the TIG arc was coarsened, and the amount of wear was significantly greater than in other areas. On the other hand, the sliding surfaces of the rocker arms treated according to the present invention (A and B) have better hardness and wear resistance than the rocker arms treated with the above-mentioned treatments C and D, and the depth of the remelted layer is also lower. It was found that it was uniform. FIG. 2 is a photograph showing a cross section of a Rocker arm that has undergone treatment A in a direction perpendicular to its longitudinal direction at a magnification of 6.2 times. As can be seen from FIG. 2, according to the above-mentioned process A, substantially the entire area of the sliding surface is uniformly remelted and uniformly hardened in a short period of time. Example 2 As in Example 1, the top surface of the valve stem of an exhaust valve to be incorporated into an automobile diesel engine was remelted and hardened. The processing conditions adopted were voltage 18V, peak current Ip=
120A, base current Ib = 20A, peak current time Tp
= 0.1 seconds, base current time Tb = 0.1 seconds, processing time 1
The exhaust valve as the material to be treated was made of heat-resistant steel (JIS standard SUH3) and weighed 105 g. When the structure of the cross section was observed after the treatment, it was found that a very fine martensitic structure was formed over substantially the entire top surface of the valve stem. From the above description, it will be understood that according to the remelting surface hardening treatment method for a metal member according to the present invention, a relatively wide area of the treated material can be hardened quickly and uniformly. Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は上述の実施例１に於ける被処理材とし
てのロツカーアームを示す斜視図、第２図は本発
明による金属部材の再溶融表面硬化処理法の好ま
しい実施例により処理されたロツカーアームの摺
動面の長手方向に垂直な断面を6.2倍にて示す写
真である。
１……ロツカーアーム、２……摺動面、３……
摺動面の中心。
FIG. 1 is a perspective view showing a rocker arm as a material to be treated in Example 1, and FIG. 2 is a diagram showing the surface of a rocker arm treated by a preferred embodiment of the remelting surface hardening treatment method for metal members according to the present invention. This is a photograph showing a cross section perpendicular to the longitudinal direction of the moving surface at 6.2x magnification. 1...Rotzker arm, 2...Sliding surface, 3...
Center of sliding surface.