JP3763089B2

JP3763089B2 - Overlay welding method

Info

Publication number: JP3763089B2
Application number: JP27717098A
Authority: JP
Inventors: 浩一光畑; 圭司上田
Original assignee: Babcock Hitachi KK
Current assignee: Mitsubishi Power Ltd
Priority date: 1998-09-30
Filing date: 1998-09-30
Publication date: 2006-04-05
Anticipated expiration: 2018-09-30
Also published as: JP2000102866A

Description

【０００１】
【発明の属する技術分野】
本発明は、肉盛溶接を行うと該肉盛溶接部に溶接割れが生じ、該溶接割れが母材の破断につながる恐れのある割れ感受性の高い材料表面上に、高硬度金属を多層肉盛溶接する技術に関する。
【０００２】
【従来の技術】
耐摩耗性が必要とされる装置、例えば火力発電用ボイラーにおいて石炭粉砕に用いられる部品として竪型ミルのローラタイヤ、テーブルセグメント、ホッパーなど被粉砕原料により表面が激しく摩耗する部分には、高クロム鋳鉄や軟鋼あるいは鋳鋼の母材表面に高硬度金属を多層肉盛溶接したものなど耐摩耗性の高い部材が用いられている。これらは使用後摩耗部分に、あるいは使用前に摩耗が予想される部分に高硬度金属を多層肉盛溶接し使用する場合がある。一般に高硬度金属の耐割れ性は低く、母材・溶接材料に関係なく高硬度金属を用いた溶接では割れの発生を避けることは困難となっており、この割れが母材内部まで進展し破断の原因となる場合がある。そこで肉盛溶接における入熱を抑え急加熱・急冷プロセスを用いて肉盛溶接部に意図的に微細な割れを発生させることにより残留応力を開放し母材への割れの進展を少なくした方法を用いた多層肉盛溶接が行われている。
【０００３】
【発明が解決しようとする課題】
上記従来方法では、肉盛溶接の入熱を低く抑えて意図的に割れを発生させる際に、図８に示すように、溶接ビードを重ねながら（ハーフラップ法）肉盛溶接をした場合、最初の溶接ビードで発生した割れが隣接する溶接ビードへ次々と伝播し、微細な割れであるが割れが縦横につながった比較的規則正しい形状となる。この方法により多層肉盛溶接を行った場合、初層で発生した割れが２層目、３層目と伸びていき肉盛溶接部表面において初層での割れ形状が再現される形になる。このような規則正しい割れ形状では溶接金属の剥離や母材破断の可能性が高くなり、例えば前述の竪型ミルのローラタイヤ、テーブルセグメントのように激しい振動の起こる部分に適用する場合に特に問題となる。
【０００４】
また従来方法では肉盛溶接の際の入熱を抑え続けることにより微細な割れを発生させているため、溶接金属量が少なく非能率的な作業となっている。
【０００５】
本発明の目的は、上記従来方法における問題点を解決し、溶接金属の剥離や母材破断の可能性が低く母材への割れの進展を最少とする肉盛溶接部を確保できる肉盛溶接方法を提供することにある。
【０００６】
また本発明の別の目的は、上記のように、溶接金属の剥離や母材破断の可能性がを低く母材への割れの進展を最少とする肉盛溶接部を確保すると共に、より溶接能率の向上を図る肉盛溶接方法を提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、本発明の肉盛溶接方法は、割れ感受性の高い材料からなる母材表面に、多パスで高硬度金属を肉盛溶接する方法において、母材表面を覆う初層を形成するため、各パスの入熱を所定値以下に制限して各パスの溶接ビードに細かい割れを発生させる溶接条件を用いて、母材表面にまず溶接ビードを並行にかつ隣合う溶接ビードを離間させて形成し、次いで隣合う溶接ビード間を両溶接ビードと重なるように溶接ビードを形成することを特徴とする。
【０００８】
上記方法により、肉盛溶接部には微細で不規則な割れを発生させることにより溶接残留応力を肉盛溶接後直ちに開放し、母材内部へ深く割れが進展せず母材を破断へ至らしめるのを防ぐことができる。
【０００９】
また上記別の目的を達成するために、本発明の別の肉盛溶接方法は、割れ感受性の高い材料からなる母材表面に、多パス多層で高硬度金属を肉盛溶接する肉盛溶接方法において、各パスの入熱を所定値以下に制限して各パスの溶接ビードに細かい割れを発生させる溶接条件を用いて、（１）母材表面にまず溶接ビードを並行にかつ隣合う溶接ビードを離間させて形成し、次いで前記隣合う溶接ビード間を該両溶接ビードと重なるように溶接ビードを形成することにより母材表面を覆う初層を形成し、（２）そして該初層上に該初層と同様に各パスの入熱を所定値以下に制限して溶接ビードを並行にかつ隣合う溶接ビードを離間させて形成し、次いで該隣合う溶接ビード間を該両溶接ビードと重なるように溶接ビードを形成することにより第２層を形成し、（３）さらに前記初層及び前記第２層よりも入熱を高くして第３層以降の肉盛溶接を行うことを特徴とする
【００１０】
上記各肉盛溶接方法は、肉盛溶接はオープンアーク溶接を用いて行うことが好ましい。また各肉盛溶接方法において、割れ感受性の高い材料は高クロム鋳鉄とし、高硬度金属は炭素を５．４ｗｔ％以下含有するものとする場合には、初層を形成する各パスの溶接入熱が２，０００Ｊ／ｃｍ未満であることが好ましい。なお、別の肉盛溶接方法において、第３層以降の入熱は２，０００Ｊ／ｃｍ以上、例えば７０００Ｊ／ｃｍ又はそれ以上にすることにより、高能率の肉盛溶接を行うことができる。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態を図面により説明する。
図１は、本発明に係る肉盛溶接方法を示す図である。割れ感受性の高い材料表面上への高硬度金属の多層肉盛溶接においては、図１(ａ)に示すように、初層を互いの溶接ビード１２、１３、１４、１５が重ならないように肉盛溶接を行い、それぞれの溶接ビードで独立した割れを発生させた後、図１(ｂ)で示すように、溶接ビード間を溶接ビード１６、１７、１８を形成して肉盛溶接することで初層肉盛溶接部表面において微細で且つ不規則な割れの発生発生させる。図中、溶接ビード長手方向に対して交叉する方向の横割れが示されている。
【００１２】
本発明による割れ感受性の高い材料表面上への高硬度金属の多層肉盛溶接を実施する自動アーク溶接装置の一例を図２に示す。この自動アーク溶接装置は、溶接制御装置１と、溶接電源２と、溶接トーチ４と、この溶接トーチ４の左右移動ユニット６及び上下移動ユニット７と、溶接トーチ４にフィード供給される溶接ワイヤ５と、溶接トーチ４、左右移動ユニット６、上下移動ユニット７、等を搭載する自走台車８と、被溶接材料（母材）３上に載置され自走台車８をガイドするレール９等から構成されている。符号１０、１１はアーク電流用パワーケーブル、アースケーブルである。この装置による溶接はオープンアークにより行う。そのため、周囲からアークや溶融池の位置、状態を容易に確認できる。
【００１３】
本発明の方法で肉盛溶接をする場合、特別な装置や技術は必要なく、従来のガスシールドアーク装置をそのまま流用できる点が強みである。
【００１４】
上記溶接装置を用いて高クロム鋳鉄（Ｃ：３ｗｔ％，Ｃｒ：２０ｗｔ％，残り Fe）に高硬度金属（Ｃ：５.２ｗｔ％，Ｃｒ：２５.３ｗｔ％，残り Fe）の多層肉盛溶接を行った。
【００１５】
表１及び図３に溶接条件を変化させ２層肉盛溶接したときの肉盛部表面における平均割れピッチと母材進展割れ深さの測定結果を示す。試験片Ｎｏ．１〜３は従来法のハーフラップ法に肉盛溶接したものであり、試験片Ｎｏ．４〜７は本発明方法（飛びパス法と称することにする）により肉盛溶接したものである。従来法のハーフラップ法で溶接入熱１２００、１５００、１８００ J／cmの各種条件で溶接した場合、平均割れピッチは、８、１０、１１mmであり、母材進展割れ深さは４、４.５、４.５mmであった。本発明の飛びパス法で同じく溶接入熱１２００、１５００、１８００ J／cmの各種条件で溶接した場合、平均割れピッチは、６、７、９mmであり、最大母材進展割れ深さは３、３、３.５mmであった。このように従来法に比べ本発明の方法で肉盛溶接した物のほうが平均割れピッチが狭く且つ母材進展割れ深さが浅いことから、溶接残留応力が最大限解放され母材への影響が極小となっていることが分かる。なお、本発明の飛びパス法により肉盛溶接したＮｏ.７は、入熱が２０００ J／cmと大きいため、平均割れピッチ１１mm、母材進展割れ深さは４.５mmと大きくなった。
【００１６】
【表１】

【００１７】
ここで、平均割れピッチは、溶接ビード長手方向に交差する横割れの間隔を平均した値を示し、測定には３０mm角のマス目を用いた。また入熱Ｊ(Ｊ／cm)は、Ｉ；溶接電流(Ａ)、Ｅ；溶接電圧(Ｖ)、ｖ；溶接速度(cm／min)とすると、次のように表される。
【００１８】
【数１】

【００１９】
次に、肉盛溶接の１、２層目を本発明の飛びパス法を用い、入熱を１８００ J／cmとして低入熱で溶接を行い、さらに２層目肉盛溶接部の上に各種入熱条件（１８００、４０３２、６０００、７９８０ J／cm）を用いて多層肉盛溶接（約２０ｍｍ）を行った。表２に溶接した試験片Ｎｏ.８〜１１、溶接条件及び母材進展割れ深さの測定結果を示す。３層目以降の肉盛溶接における入熱を増加させても、母材進展割れ深さの最大値は３.５mmと一定であり、増加していないことが分かる。これは、初層で形成した微細で且つ不規則な割れが２層目以降に次々と伝播することで、肉盛溶接における入熱を低く抑え続けなくとも、溶接残留応力の解放が可能であることを示している。
【００２０】
【表２】

【００２１】
図４に試験片を母材表面に対して垂直方向に切断した一断面における割れ状態を、図５に試験片を母材表面と平行に切断した一断面（多層肉盛の約２０ｍｍ厚さのほぼ半分にあたる面位置）における割れ状態を示す。
【００２２】
この高硬度金属の肉盛溶接により、溶接部に十分な耐摩耗性が確保できていることを確認するために、肉盛溶接部に対して摩耗試験を実施した。摩耗試験は、図６に示すように、試験片１９に対して錘２２により荷重をかけ、試験片１９とゴムライニングホイールとの間に珪砂を供給して相互に回転させ摩擦させて行った。供試材は表２に示す試験片Ｎｏ.８〜１１である。表３に摩耗試験の条件を、表４及び図７には摩耗試験結果を示す。
【００２３】
【表３】

【００２４】
耐摩耗性を母材（高クロム鋳鉄）の摩耗量を各試験片の摩耗量で除した数値（比）で示すと、母材の１に対して、試験片Ｎｏ.８〜１１は、１.６９、２.４５、２.７５となる。この試験結果から、高硬度金属の肉盛溶接部は母材１より耐摩耗性に優れ、肉盛溶接時の入熱量の増加に伴い耐摩耗性も増加していることが分かる。これは、入熱量の増加に伴い溶接金属中の炭化物の結晶成長が促進されるためである。しかし、耐摩耗性の増加、すなわち溶接金属中の炭化物の結晶成長には上限があり、むやみに肉盛溶接時の入熱を増加させてもある程度以上の耐摩耗製の増加は期待できない。逆に、肉盛溶接時の入熱を増加させすぎると、残留応力の解放が十分に行われず、結果として母材の破断につながる可能性がある。従って、本高硬度金属の肉盛溶接時の入熱は１０，０００Ｊ／ｃｍ程度が上限であると考える。
【００２５】
【発明の効果】
本発明によれば、割れ感受性の高い材料からなる母材表面に高硬度金属を肉盛溶接する肉盛溶接方法を、初層の形成時に、低入熱で母材３表面にまず溶接ビードを並行にかつ隣合う溶接ビードを離間させて形成し、次いで隣合う溶接ビード間を両溶接ビードと重なるように溶接ビードを形成するものとするので、肉盛溶接部に微細で不規則な割れを発生させ、溶接残留応力を溶接後直ちに開放し、溶接金属の剥離や母材内部へ深く割れが進展するのを防ぐことができるという効果がある。
【００２６】
また本発明によれば、別の肉盛溶接方法を、上記肉盛溶接方法と同じ要領で初層、第２層を形成し、第３層以降はより大きな入熱で溶接ビードを形成するものとしたので、上記のように割れの進展を防ぐと共に、高能率の肉盛溶接を行うことができるという効果がある。
【図面の簡単な説明】
【図１】本発明の溶接肉盛方法による溶接ビードの形成順序と肉盛溶接部表面の割れ形状を示す図である。
【図２】本発明を実施する溶接装置の一例を示す図である。
【図３】本発明の方法及び従来方法によりそれぞれ形成した第２層溶接部表面での平均割れピッチと母材進展割れ深さを比較する図である。
【図４】本発明の溶接肉盛方法により形成した肉盛溶接部を母材表面に対して垂直に切断した断面での割れを示す図である。
【図５】本発明の溶接肉盛方法により形成した肉盛溶接部を母材表面と平行に切断した断面での割れを示す図である。
【図６】硬化肉盛溶接部の摩耗試験を行う実験装置を示す図である。
【図７】本発明の溶接肉盛方法により形成した肉盛溶接部の摩耗試験結果を示す図である。
【図８】従来のハーフラップ法による溶接ビードの形成順序と肉盛溶接部表面の割れ形状を示す図である。
【符号の説明】
１溶接制御装置
２溶接電源
３母材
４溶接トーチ
５溶接ワイヤ
８自走台車
１２〜１８溶接ビード
２３肉盛溶接部
２４割れ[0001]
BACKGROUND OF THE INVENTION
In the present invention, when overlay welding is performed, weld cracking occurs in the overlay weld, and the weld crack is likely to lead to fracture of the base material. It relates to welding technology.
[0002]
[Prior art]
In parts where wear resistance is required, such as boilers for thermal power generation, parts used for coal crushing, such as roller tires of vertical mills, table segments, hoppers, etc. A member with high wear resistance such as cast iron, mild steel, or a cast metal base material having a high-hardness metal multi-layer welded on its surface is used. In some cases, a high-hardness metal is multilayered and welded to a worn part after use or a part where wear is expected before use. Generally, high-hardness metals have low cracking resistance, and it is difficult to avoid cracking when welding with high-hardness metals regardless of the base metal and welding material. It may cause. Therefore, a method that suppresses heat input in overlay welding and intentionally generates fine cracks in the weld overlay using a rapid heating / quenching process to release residual stress and reduce the development of cracks in the base metal. The used multi-layer welding is performed.
[0003]
[Problems to be solved by the invention]
In the above conventional method, when cracks are intentionally generated while keeping the heat input of overlay welding low, as shown in FIG. 8, when overlay welding is performed with the weld beads stacked (half lap method), The cracks generated in the weld beads propagate to the adjacent weld beads one after another, and become a relatively regular shape that is a fine crack but is connected vertically and horizontally. When multilayer build-up welding is performed by this method, the crack generated in the first layer extends to the second and third layers, and the crack shape in the first layer is reproduced on the surface of the build-up weld. Such a regular crack shape increases the possibility of peeling of the weld metal and the fracture of the base metal, which is particularly problematic when applied to portions where intense vibrations occur, such as the roller tires of the above-mentioned vertical mills and table segments. Become.
[0004]
Moreover, in the conventional method, since fine cracks are generated by continuously suppressing heat input during overlay welding, the amount of weld metal is small and the work is inefficient.
[0005]
The object of the present invention is to solve the problems in the conventional methods described above, and build-up welding that can secure a built-up weld that minimizes the progress of cracks to the base metal with low possibility of peeling of the weld metal and breakage of the base metal It is to provide a method.
[0006]
Another object of the present invention, as described above, is to secure a welded weld that minimizes the progress of cracking to the base metal with a low possibility of welding metal peeling and base metal breakage, and more welding. An object of the present invention is to provide an overlay welding method for improving the efficiency.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the overlay welding method of the present invention is the first layer covering the base material surface in the method of overlay welding a high-hardness metal in multiple passes to the base material surface made of a material having high cracking sensitivity. In order to form a weld bead in parallel and adjacent to the base metal surface using welding conditions that limit the heat input of each pass to a predetermined value or less and generate fine cracks in the weld bead of each pass. The weld beads are formed so as to be separated from each other, and the weld beads are then overlapped with each other between the adjacent weld beads.
[0008]
By the above method, the weld residual stress is released immediately after build-up welding by generating fine and irregular cracks in the build-up weld, and cracks do not propagate deeply into the base metal, leading to fracture of the base metal Can be prevented.
[0009]
In order to achieve the above-mentioned another object, another overlay welding method of the present invention is an overlay welding method for overlay welding a high-hardness metal in a multi-pass multilayer to a base material surface made of a material having high cracking sensitivity. (1) Welding beads adjacent to the base material surface in parallel and adjacent to each other using welding conditions that limit the heat input of each pass to a predetermined value or less and cause fine cracks in the weld beads of each pass. Forming an initial layer covering the base material surface by forming a weld bead so as to overlap the weld bead between the adjacent weld beads, and (2) on the initial layer. As with the first layer, the heat input of each pass is limited to a predetermined value or less, and weld beads are formed in parallel and adjacent weld beads are separated from each other, and the adjacent weld beads are then overlapped with the two weld beads. Second by forming the weld bead as Forming a, [0010], wherein (3) the carrying out the high to overlaying welding of the third and subsequent layers may heat input from the first layer and the second layer further
In each of the overlay welding methods, the overlay welding is preferably performed using open arc welding. Also, in each overlay welding method, if the material with high cracking sensitivity is high chromium cast iron and the hard metal contains 5.4 wt% or less of carbon, the welding heat input of each pass forming the first layer Is preferably less than 2,000 J / cm. In another build-up welding method, high-efficiency build-up welding can be performed by setting the heat input after the third layer to 2,000 J / cm or more, for example, 7000 J / cm or more.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a build-up welding method according to the present invention. In multi-layer overlay welding of a high-hardness metal on the surface of a material that is highly susceptible to cracking, as shown in FIG. 1 (a), the first layer is welded so that the

weld beads

12, 13, 14, and 15 do not overlap each other. After performing weld welding and generating independent cracks in each weld bead, as shown in FIG. 1 (b),

welding beads

16, 17, and 18 are formed between the weld beads, and overlay welding is performed. Generation of fine and irregular cracks on the surface of the first layer overlay weld. In the figure, transverse cracks in the direction crossing the longitudinal direction of the weld bead are shown.
[0012]
FIG. 2 shows an example of an automatic arc welding apparatus for performing multi-layer overlay welding of a hard metal on a material surface having high crack sensitivity according to the present invention. The automatic arc welding apparatus includes a welding control device 1, a welding power source 2, a welding torch 4, a left / right moving unit 6 and a vertical moving unit 7 of the welding torch 4, and a welding wire 5 fed to the welding torch 4. And a self-propelled carriage 8 on which the welding torch 4, the left and right moving unit 6, the vertical moving unit 7, and the like are mounted, and a rail 9 that is placed on the material to be welded (base material) 3 and guides the self-propelled carriage 8. It is configured. Reference numerals 10 and 11 denote an arc current power cable and an earth cable. Welding with this device is performed by open arc. Therefore, the position and state of the arc and the molten pool can be easily confirmed from the surroundings.
[0013]
When overlay welding is performed by the method of the present invention, no special device or technique is required, and the advantage is that a conventional gas shield arc device can be used as it is.
[0014]
Multi-layer overlay welding of high-hardness metal (C: 5.2 wt% , Cr: 25.3 wt% , remaining Fe ) to high chromium cast iron (C: 3 wt%, Cr: 20 wt%, remaining Fe ) using the above welding equipment Went.
[0015]
Table 1 and FIG. 3 show the measurement results of the average crack pitch and the base material progress crack depth on the surface of the built-up part when the welding conditions are changed and two-layer build-up welding is performed. Specimen No. Nos. 1 to 3 are overlay welded to the conventional half lap method. Nos. 4 to 7 are overlay welded by the method of the present invention (hereinafter referred to as the jump pass method). When welding under various conditions of

welding heat input

1200, 1500, 1800 J / cm by the conventional half lap method, the average crack pitch is 8, 10, 11 mm, and the base metal progress crack depth is 4, 4. 5, 4.5 mm. Similarly, when welding under various conditions of

welding heat input

1200, 1500, 1800 J / cm in the jump path method of the present invention, the average crack pitch is 6, 7, 9 mm, and the maximum base material progress crack depth is 3, 3, 3.5 mm. Thus, compared to the conventional method, the weld welded by the method of the present invention has a narrower average crack pitch and shallower base metal crack depth, so that the residual welding stress is released to the maximum and the influence on the base metal is reduced. It can be seen that it is minimal. In addition, No. 7, which was overlay welded by the jumping path method of the present invention, had a large heat input of 2000 J / cm, and therefore the average crack pitch was 11 mm and the base material progress crack depth was as large as 4.5 mm.
[0016]
[Table 1]

[0017]
Here, the average crack pitch shows the value which averaged the space | interval of the transverse crack which cross | intersects a weld bead longitudinal direction, and the 30 square mm square was used for the measurement. The heat input J (J / cm) is expressed as follows, where I: welding current (A), E: welding voltage (V), v: welding speed (cm / min).
[0018]
[Expression 1]

[0019]
Next, the first and second layers of the overlay welding are welded at a low heat input with a heat input of 1800 J / cm using the jump path method of the present invention. Multi-layer overlay welding (about 20 mm) was performed using heat input conditions (1800, 4032, 6000, 7980 J / cm). Table 2 shows the measurement results of welded test pieces Nos. 8 to 11, welding conditions, and base metal crack depth. It can be seen that even if the heat input in overlay welding of the third and subsequent layers is increased, the maximum value of the base material progress crack depth is constant at 3.5 mm and does not increase. This is because the fine and irregular cracks formed in the first layer propagate one after another in the second layer, so that it is possible to release the welding residual stress without keeping the heat input in overlay welding low. It is shown that.
[0020]
[Table 2]

[0021]
FIG. 4 shows a cracked state in one cross section obtained by cutting the test piece in a direction perpendicular to the base material surface, and FIG. 5 shows a cross section in which the test piece is cut in parallel with the base material surface. The cracking state at the surface position corresponding to approximately half) is shown.
[0022]
In order to confirm that sufficient wear resistance was ensured in the welded portion by overlay welding of the high hardness metal, a wear test was performed on the overlay welded portion. As shown in FIG. 6, the wear test was performed by applying a load to the test piece 19 with a weight 22, supplying quartz sand between the test piece 19 and the rubber lining wheel, and rotating and rubbing each other. The test materials are test pieces Nos. 8 to 11 shown in Table 2. Table 3 shows the conditions of the wear test, and Table 4 and FIG. 7 show the results of the wear test.
[0023]
[Table 3]

[0024]
When the wear resistance is indicated by a numerical value (ratio) obtained by dividing the wear amount of the base material (high chromium cast iron) by the wear amount of each test piece, the test pieces No. 8 to 11 are 1 for the base material 1 .69, 2.45, 2.75. From this test result, it can be seen that the build-up welded portion of the high-hardness metal is superior to the base material 1 in wear resistance, and the wear resistance is increased with the increase in heat input during build-up welding. This is because the crystal growth of carbides in the weld metal is promoted as the heat input increases. However, there is an upper limit to the increase in wear resistance, that is, the crystal growth of carbides in the weld metal, and even if the heat input during build-up welding is increased, an increase in wear resistance beyond a certain level cannot be expected. Conversely, if the heat input during overlay welding is increased too much, the residual stress is not sufficiently released, and as a result, the base material may be broken. Therefore, it is considered that the upper limit of the heat input during overlay welding of the high hardness metal is about 10,000 J / cm.
[0025]
【The invention's effect】
According to the present invention, a build-up welding method in which high-hardness metal is build-up welded to a surface of a base material made of a material having high cracking sensitivity, and a weld bead is first applied to the surface of the base material 3 with low heat input when the first layer is formed. In parallel, adjacent weld beads are formed apart from each other, and then the adjacent weld beads are formed so as to overlap the two weld beads. It is possible to generate the weld residual stress immediately after welding, and to prevent peeling of the weld metal and deep cracks inside the base material.
[0026]
According to the present invention, another overlay welding method is the same as the overlay welding method in which the first layer and the second layer are formed, and the third and subsequent layers form a weld bead with a larger heat input. As described above, there is an effect that it is possible to prevent the progress of cracks as described above and to perform highly efficient overlay welding.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a welding bead formation order and a cracked shape of a surface of a weld weld by a weld overlay method of the present invention.
FIG. 2 is a view showing an example of a welding apparatus for carrying out the present invention.
FIG. 3 is a diagram comparing an average crack pitch and a base material progress crack depth at the surface of a second layer weld formed by the method of the present invention and the conventional method, respectively.
FIG. 4 is a diagram showing a crack in a cross section obtained by cutting a build-up weld formed by the weld build-up method of the present invention perpendicularly to the surface of a base material.
FIG. 5 is a diagram showing a crack in a cross section obtained by cutting a build-up weld formed by the weld build-up method of the present invention in parallel with the surface of a base material.
FIG. 6 is a view showing an experimental apparatus for performing a wear test of a hardfacing welded portion.
FIG. 7 is a diagram showing a result of a wear test of a weld overlay formed by the weld overlay method of the present invention.
FIG. 8 is a diagram showing the formation order of weld beads by the conventional half lap method and the crack shape on the surface of the weld overlay.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Welding control apparatus 2 Welding power source 3 Base material 4 Welding torch 5 Welding wire 8 Self-propelled carriage 12-18 Weld bead 23 Overlay welding part 24 Crack

Claims

In the build-up welding method in which high-hardness metal is build-up welded to the base metal surface made of a material with high cracking susceptibility in multiple passes, the heat input of each pass is set to a predetermined value to form the first layer covering the base metal surface. Using welding conditions that limit the following to generate fine cracks in the weld beads of each pass, first, weld beads are formed on the base material surface in parallel and adjacent weld beads are separated, and then the adjacent welds are formed. A build-up welding method comprising forming a weld bead so that a gap between the beads overlaps with the two weld beads.

In the overlay welding method in which high-hardness metal is overlay welded in multiple passes on the surface of a base material made of a material that is highly susceptible to cracking, the heat input in each pass is limited to a predetermined value or less and fine cracks are made in the weld bead in each pass. First, a weld bead is formed on the surface of the base material in parallel and with adjacent weld beads spaced apart from each other, and then the weld beads are overlapped with each other between the adjacent weld beads. Forming an initial layer covering the surface of the base material, and restricting the heat input of each pass to a predetermined value or less in the same manner as the initial layer on the initial layer to weld the weld beads in parallel and adjacent to each other. formed by separating the bead, then a second layer is formed by forming a weld bead so as to overlap with both said weld bead between該隣fit weld bead, than the first layer and the second layer further third and subsequent layers of meat by increasing the heat input Overlay welding wherein the welding is performed.

The build-up welding method according to claim 1, wherein the build-up welding is performed using open arc welding.

The overlay welding method according to claim 1 or 2, wherein the material having high cracking sensitivity is high chromium cast iron.

The multilayer overlay welding method according to claim 1 or 2, wherein welding heat input of each pass forming the first layer is less than 2,000 J / cm.