JPH0450110B2

JPH0450110B2 -

Info

Publication number: JPH0450110B2
Application number: JP5240484A
Authority: JP
Inventors: Fumio Hataya; Yoshiteru Chiba
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1984-03-21
Filing date: 1984-03-21
Publication date: 1992-08-13
Also published as: JPS60199594A

Description

[Detailed description of the invention]

〔発明の利用分野〕本発明は軽水炉機器用不活性ガスアーク肉盛溶
接棒に関し、更に詳細には、軽水炉機器、例えば
ジエツトポンプ摺合部及びバルブ摺合面等耐摩耗
性、耐食性の要求される部分に不活性ガスアーク
により肉盛溶接する溶接棒に関する。〔発明の背景〕軽水炉の炉水を循環させるジエツトポンプにお
いて、その上半部（アダプター）と下半部（デイ
フユーザー）は直径の異なる円筒状の部分が嵌合
された状態にあり、嵌合部が振動によつて摩擦を
うけ、また隙間を高温高圧水が高速で流動する。
またバルブはその摺合面を開放して高温高圧水あ
るいは水蒸気が高速で流動し、あるいは摺合面を
閉塞する。したがつて、ジエツトポンプ接合部、
これを支持するウエツジ及びバルブ摺合部の肉盛
溶接部は、硬さ、耐摩耗性、高温水中耐食性、耐
エロージヨン性がすぐれていることが要求され
る。また、肉盛溶接部は１層では母材（ジエツト
ポンプ、バルブの材質は一般には17Cr−12Ni−
2Mo系や18Cr−8Ni系のステンレス鋼である。）
の希釈を受け、肉盛溶接棒本来の硬さが得られ
ず、２層あるいは３層の溶接が必要である。更に、これらの機器用の肉盛溶接棒としては一
般にCo基の耐摩耗合金が使用されているが、Co
基合金溶接棒は軽水炉の高温高圧水あるいは蒸気
の高速流体に接しているので腐食、エロージヨン
によつてCoが炉水中に溶出し、また金属同士の
摩耗によつてCoが炉水中に混入する。これらの
Coは炉心に入り、 ⁶⁰Coとなり、配管、タービン
その他の機器に循環、付着し、放射能を上げると
いう欠点がある。 Co基耐摩耗溶接棒の代りに、1.5C−4Si−15Cr
−6Mo−0.1B−Niあるいは1C−1Si−30Cr−
18W−NiなどのNi基耐摩耗溶接棒が開発されて
いる。しかしこれらの溶接棒の溶接性は必ずしも
十分とはいえず、特に多層溶接時に溶接割れを発
生し易い。またＢ（ほう素）は中性子照射によりHeを生じ
脆くなるので、Ｂ含有合金の溶接棒は炉外の配管
バルブには使えるが、炉内のジエツトポンプには
使えない。したがつて、炉容器内機器用溶接棒に
はＢを含んでいないことが必要である。〔発明の目的〕本発明は前記の軽水炉機器用不活性ガスアーク
溶接棒の欠点を解決するためになされたもので、
その目的は硬さを低下することなく溶接性を改善
し、３層肉盛溶接が可能な軽水炉機器用肉盛溶接
棒を提供することである。〔発明の概要〕本発明について概説すると、本発明は重量％で
C0.55〜1.20％、Si0.2〜0.6％、Mn0.2〜1.0％、
Cr28〜32％、W16〜21％、Fe4〜10％、残部がNi
及び不可避不純物よりなる組成を有することを特
徴とする軽水炉機器用不活性ガスアーク肉盛溶接
棒に関する。本発明の溶接棒の成分組成は、その用途上、
Co及びＢ成分を含まないNi基合金の組成を改善
したものであり、各成分の作用は既知のNi基合
金の溶接棒の性質に及ぼす各成分の作用と本質的
には異なるものではないが、その各成分の重量％
での割合の下限及び上限の数値はその硬さ（ビツ
カース硬度Hv）380以上及び溶接性（３層肉盛溶
接の際に溶接割れの発生がないこと）の両者を満
足する条件として採択されたものである。そして
前記の各成分の数値範囲において、C0.8〜1.1％、
Si0.2〜0.5％、Mn0.2〜0.7％、Cr28〜32％、W17
〜19％、Fe4〜８％、残部がNi及び不可避不純物
である場合には、その溶接状態における硬さが
Hv400以上でありしかも溶接性が良好であること
が認められた。次に成分組成の限定理由について説明する。Ｃ
はCr及びＷと炭化物を形成し、また一部は基地
に固溶して材料の硬さ及び耐摩耗性を向上する。
0.55％未満ではこれらの十分な性質が得られず、
また1.20％を超えると靱性が低下し、溶接割れを
生じ易くなるので0.55〜1.20％とし、0.8〜1.1％
が好ましい。 Siは溶接時の脱酸作用及び流動性を与えるため
に必要であり、0.2％未満ではこれらの性能が十
分でなく、また0.6％を超えると靱性の低下及び
組織の粗大化をもたらし、かつ溶接割れが生じ易
くなれので0.2〜0.6％とする。従来、表面硬化肉
盛溶接棒では硬さを付与するためSiは約１％ある
いはＢと共存する場合は４％含むものが多かつた
が、本発明では溶接割れを生じないためその上限
を0.6％とし、この他にＣ、Cr及びＷの適正量を
選べば、低Siでも十分な硬さが得られるようにし
た。0.2〜0.5％が好ましい。 Mnは脱酸及び脱硫作用を有し、溶接割れを生
じ難くするが、0.2％未満ではその作用が十分で
なく、また1.0％を超えるとその作用は飽和する
ので、0.2〜1.0％とし、0.2〜0.7％が好ましい。 Crは高温高圧水あるいは水蒸気中における耐
食性を向上し、また炭化物を形成して硬さ、耐摩
耗性、耐焼付性及び耐エロージヨン性を向上す
る。28％未満ではこれらの性能が十分でなく、ま
た32％を超えると靱性が低下するので28〜32％と
する。Ｗは炭化物を形成して硬さ、耐摩耗性、耐焼付
性及び耐エロージヨン性を向上するのに必須の元
素であり、16％より少なくてはこれらの性能が十
分でなく、また21％を超えると靱性が低下し、か
つ溶接割れが生じ易くなるので16〜21％とし、17
〜19％が好ましい。 FeはNi基合金に添加して溶接性を向上させ、
またコストを低減させるが、４％未満ではこれら
の作用が十分でなく、また10％を超えると硬さ及
び耐摩耗性が低下するので４〜10％とし、４〜８
％が好ましい。残部のNiは基地を構成する主要元素であり、
強度、靱性及び耐食性の保持に必要である。Ni
基溶接棒なので、従来のCo基溶接棒と異なり、
たとえ少量の溶出あるいは摩耗があつたにして
も、それはNiを主成分としたものであり、Coは
不純物程度なので ⁶⁰Coによる放射能上昇は非常
に少ない。前記組成のNi基合金はその数値範囲内で種々
の組成をとりうるが、バルブ摺合面やジエツトポ
ンプ嵌合部は摩耗、エロージヨンを受けやすいの
で高硬度が必要である。十分な耐摩耗性及び耐エ
ロージヨン性を得るにはビツカース硬さ380以上
が必要であり、400以上が望ましい。そして、前記Ni基合金を不活性ガスアークに
より３層肉盛溶接した場合、前記したように肉盛
溶接部は母材の希釈を受けるので１層溶接ではそ
の溶接棒本来の性質を示さないが、２層溶接で希
釈の影響が小さくなり、３層溶接で希釈の影響を
無視できる。したがつて肉盛溶接用には溶接割れ
を生じることなく、３層溶接できることが必要で
ある。〔発明の実施例〕次に本発明の溶接棒を比較例と対比して説明す
る。実施例及び比較例における溶接棒の成分組成は
下記の表に示すとおりであり、大気中溶解鋳造法
により製造したφ5mmの鋳造溶接棒である。下記
の表には硬さ（ビツカース硬度Hv）及び溶接性
を併記した。溶接性の試験は３層肉盛溶接の平面図である第
１図及びその側面図である第２図に示すように、
母材１として100×250×40tmmのSUS304鋼板を用
い、次に母材１の表面に各溶接棒を60×150mmの
範囲に１層溶接２を行ない、次いで60×100mmに
２層溶接３を行ない、最後に60×50mmに３層溶接
４を行なつた。溶接方法はTIG溶接法（タングス
テン電極不活性ガスアーク溶接法）により、母材
の予熱及びパス間温度を400℃とした。この種の
表面硬化肉盛溶接棒は予熱及びパス間温度の高い
程溶接割れを生じにくくなるが、予熱温度及びパ
ス間温度を500℃以上にすると溶接環境が悪化し、
かつ溶接時の熱サイクルと重畳して熱影響部が鋭
敏化する恐れがあるので400℃にした。 [Field of Application of the Invention] The present invention relates to an inert gas arc build-up welding rod for light water reactor equipment, and more specifically, for light water reactor equipment, for example, parts that require wear resistance and corrosion resistance such as jet pump sliding parts and valve sliding faces. This invention relates to a welding rod for overlay welding using an active gas arc. [Background of the Invention] In a jet pump that circulates reactor water in a light water reactor, its upper half (adapter) and lower half (diff user) are fitted with cylindrical parts with different diameters. The parts are subjected to friction due to vibration, and high-temperature, high-pressure water flows at high speed through the gaps.
Further, the valve opens its sliding surface to allow high-temperature, high-pressure water or steam to flow at high speed, or closes the sliding surface. Therefore, the jet pump junction,
The overlay welds of the wedges and valve sliding parts that support this are required to have excellent hardness, wear resistance, high temperature underwater corrosion resistance, and erosion resistance. In addition, in the overlay welding of one layer, the base material (jet pumps and valves are generally made of 17Cr-12Ni-
These are 2Mo-based or 18Cr-8Ni-based stainless steels. )
Due to the dilution of the overlay welding rod, the original hardness of the overlay welding rod cannot be obtained, and two or three layers of welding are required. Furthermore, Co-based wear-resistant alloys are generally used as overlay welding rods for these devices;
Since base alloy welding rods are in contact with high-speed fluids such as high-temperature, high-pressure water or steam in light water reactors, Co is eluted into the reactor water through corrosion and erosion, and Co is mixed into the reactor water due to metal-to-metal wear. these
Co enters the reactor core, becomes ⁶⁰ Co, circulates and adheres to piping, turbines, and other equipment, and has the disadvantage of increasing radioactivity. 1.5C−4Si−15Cr instead of Co-based wear-resistant welding rod
−6Mo−0.1B−Ni or 1C−1Si−30Cr−
Ni-based wear-resistant welding rods such as 18W-Ni have been developed. However, the weldability of these welding rods is not necessarily sufficient, and weld cracks are likely to occur particularly during multilayer welding. Furthermore, B (boron) becomes brittle when irradiated with neutrons, so welding rods made of B-containing alloys can be used for pipe valves outside the furnace, but cannot be used for jet pumps inside the furnace. Therefore, it is necessary that the welding rod for equipment inside the furnace vessel does not contain B. [Object of the Invention] The present invention was made in order to solve the above-mentioned drawbacks of the inert gas arc welding rod for light water reactor equipment.
The purpose is to provide an overlay welding rod for light water reactor equipment that improves weldability without reducing hardness and is capable of three-layer overlay welding. [Summary of the Invention] To outline the present invention, the present invention can be summarized as follows.
C0.55~1.20%, Si0.2~0.6%, Mn0.2~1.0%,
Cr28~32%, W16~21%, Fe4~10%, balance Ni
and an inert gas arc build-up welding rod for light water reactor equipment, characterized by having a composition consisting of unavoidable impurities. The composition of the welding rod of the present invention is as follows:
This is an improved composition of a Ni-based alloy that does not contain Co and B components, and the effects of each component are not essentially different from the effects of each component on the properties of known Ni-based alloy welding rods. , weight% of each component thereof
The lower and upper limits of the ratio were adopted as conditions that satisfy both the hardness (Bitzkers hardness Hv) of 380 or higher and weldability (no weld cracking occurs during three-layer overlay welding). It is something. And in the numerical range of each component above, C0.8~1.1%,
Si0.2~0.5%, Mn0.2~0.7%, Cr28~32%, W17
~19%, Fe4~8%, and the remainder is Ni and unavoidable impurities, the hardness in the welded state is
It was found that the weldability was higher than Hv400 and that the weldability was good. Next, the reason for limiting the component composition will be explained. C
forms a carbide with Cr and W, and some of it is dissolved in the matrix to improve the hardness and wear resistance of the material.
If it is less than 0.55%, these sufficient properties cannot be obtained,
In addition, if it exceeds 1.20%, the toughness will decrease and weld cracks will easily occur, so it should be set at 0.55 to 1.20%, and 0.8 to 1.1%.
is preferred. Si is necessary to provide deoxidizing effect and fluidity during welding, and if it is less than 0.2%, these properties are insufficient, and if it exceeds 0.6%, it will cause a decrease in toughness and coarsening of the structure, and will cause welding problems. It is set at 0.2 to 0.6% since it tends to cause cracks. Conventionally, surface-hardened overlay welding rods often contained about 1% Si or 4% Si when coexisting with B to impart hardness, but in the present invention, the upper limit was set to 0.6 to prevent weld cracking. %, and by selecting appropriate amounts of C, Cr, and W, sufficient hardness can be obtained even with low Si. 0.2-0.5% is preferred. Mn has a deoxidizing and desulfurizing effect and makes it difficult to cause weld cracking, but if it is less than 0.2%, this effect is insufficient, and if it exceeds 1.0%, the effect is saturated, so it should be set at 0.2 to 1.0%, and 0.2%. ~0.7% is preferred. Cr improves corrosion resistance in high-temperature, high-pressure water or steam, and forms carbides to improve hardness, wear resistance, seizure resistance, and erosion resistance. If it is less than 28%, these properties are insufficient, and if it exceeds 32%, the toughness decreases, so it is set to 28 to 32%. W is an essential element to form carbides and improve hardness, wear resistance, seizure resistance, and erosion resistance; if it is less than 16%, these properties are insufficient, and if it is less than 21%. If it exceeds 16% to 21%, the toughness decreases and weld cracking is more likely to occur.
~19% is preferred. Fe is added to Ni-based alloys to improve weldability.
It also reduces costs, but if it is less than 4%, these effects will not be sufficient, and if it exceeds 10%, hardness and wear resistance will decrease, so it should be set at 4 to 10%, and 4 to 8%.
% is preferred. The remaining Ni is the main element constituting the base,
Necessary for maintaining strength, toughness and corrosion resistance. Ni
Since it is a base welding rod, unlike the conventional Co base welding rod,
Even if there is a small amount of elution or abrasion, the increase in radioactivity due to ⁶⁰ Co is extremely small because the main component is Ni and Co is only an impurity. The Ni-based alloy having the above composition can have various compositions within the numerical range, but high hardness is required since the valve sliding surface and the jet pump fitting part are susceptible to wear and erosion. To obtain sufficient wear resistance and erosion resistance, a Vickers hardness of 380 or higher is required, and 400 or higher is desirable. When three-layer overlay welding is performed on the Ni-based alloy using an inert gas arc, as mentioned above, the overlay weld is subject to dilution of the base metal, so single-layer welding does not exhibit the original properties of the welding rod. With two-layer welding, the effect of dilution is small, and with three-layer welding, the effect of dilution can be ignored. Therefore, for overlay welding, it is necessary to be able to weld three layers without causing weld cracks. [Embodiments of the Invention] Next, the welding rod of the present invention will be explained in comparison with a comparative example. The compositions of the welding rods in Examples and Comparative Examples are shown in the table below, and are cast welding rods with a diameter of 5 mm manufactured by an atmospheric melting and casting method. The table below also lists the hardness (Vickers hardness Hv) and weldability. The weldability test was conducted as shown in Figure 1, which is a plan view of three-layer overlay welding, and Figure 2, which is a side view thereof.
Using a 100 x 250 x 40 tmm SUS304 steel plate as the base material 1, weld one layer 2 on the surface of the base material 1 using each welding rod in an area of 60 x 150 mm, and then perform two layer weld 3 on the 60 x 100 mm area. Finally, three-layer welding 4 was performed to 60 x 50 mm. The welding method was TIG welding (tungsten electrode inert gas arc welding), with preheating of the base metal and interpass temperature of 400°C. This type of surface-hardened welding electrode becomes less prone to weld cracking as the preheating and interpass temperatures are higher, but if the preheating temperature and interpass temperature are higher than 500℃, the welding environment deteriorates.
The temperature was set at 400°C because there was a risk that the heat affected zone would become more sensitive due to the thermal cycle during welding.

〔Effect of the invention〕

以上の説明から明らかなように、本発明の溶接
棒はCo、Ｂを含まない点で軽水炉機器用溶接棒
としての要件を満すばかりでなく、その硬さ及び
３層肉盛適性を兼備している点で優れている。 As is clear from the above description, the welding rod of the present invention not only satisfies the requirements as a welding rod for light water reactor equipment in that it does not contain Co and B, but also has hardness and suitability for three-layer overlay. It is excellent in that it is

[Brief explanation of the drawing]

第１図は溶接性試験の積層を示す平面図、第２
図はその側面図、第３図は従来の溶接棒No.３の電
子顕微鏡組織写真、第４図は本発明の溶接棒No.６
の電子顕微鏡組織写真である。第１図及び第２図中、１……母材、２……１層
溶接、３……２層溶接、４……３層溶接。 Figure 1 is a plan view showing the lamination for the weldability test, Figure 2
The figure is a side view, Figure 3 is an electron micrograph of the conventional welding rod No. 3, and Figure 4 is the welding rod No. 6 of the present invention.
This is an electron micrograph of the structure. In Figures 1 and 2, 1...Base metal, 2...1 layer welding, 3...2 layer welding, 4...3 layer welding.

Claims

[Claims]

1% by weight: C0.55-1.20%, Si0.2-0.6%,
Mn0.2~1.0%, Cr28~32%, W16~21%, Fe4~
An inert gas arc overlay welding rod for light water reactor equipment, characterized by having a composition of 10% Ni and the balance consisting of Ni and unavoidable impurities.