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    科學技術論文

    焊接缺陷的產生原因及預防策略

    時間:2019年04月19日 所屬分類:科學技術論文 點擊次數:

    摘要:焊接是生產各類鑄件、鍛件及鋼結構件的一道重要工序,焊接質量的好壞對產品的性能及穩定性有直接的影響,提高焊接質量對企業發展的重要性不言而喻。基于此,本文分析了焊接缺陷產生的原因,提出了有效預防焊接缺陷的策略,希望本文能為企業提高焊接質量

      摘要:焊接是生產各類鑄件、鍛件及鋼結構件的一道重要工序,焊接質量的好壞對產品的性能及穩定性有直接的影響,提高焊接質量對企業發展的重要性不言而喻。基于此,本文分析了焊接缺陷產生的原因,提出了有效預防焊接缺陷的策略,希望本文能為企業提高焊接質量提供一些有益的參考和借鑒。

      關鍵詞:焊接缺陷;焊接質量;預防策略

    焊接技術

      隨著自動化焊接技術的發展,機械手臂焊接逐漸代替了傳統焊接方式,但在部分產品加工中,手工電弧焊仍然具有不可代替的作用,尤其是在鋼結構件焊接方面,手工現場焊接仍占有重要地位。但在焊接過程中,受制于材料、設備、人工操作和工藝等方面的原因,焊接質量不高,一些焊接指標超標,對焊件使用壽命和質量造成了嚴重影響。

      一、焊接缺陷的產生原因

      (一)焊機性能焊機性能對焊接質量有直接影響,假如焊機性能不穩定,焊接條件不佳,就很難焊出優質的焊縫。在焊機電壓不穩、電弧推力不足的情況下,焊接無法正常進行,焊接質量自然無從談起。

      (二)焊接電流焊接電流會對焊接質量造成很大程度的影響。大電流焊接可增加熔深,提高效率,但易出現燒穿、焊瘤、成形差、咬邊等缺陷;利用小電流焊接,電弧穿力小,易出現未熔合、夾渣、未焊透等缺陷。

      (三)焊接速度焊接速度過快時,熔池溫度過低,母材和焊縫不能完全熔透,會出現未焊透、未熔合和焊縫不良等焊接缺陷。焊接速度過慢時,熔池溫度過高,易造成焊渣倒流,形成夾渣缺陷,還會增加熱影響區寬度,焊接接頭的晶粒變粗大,力學性能下降,且會增加焊接的變形量。

      (四)電弧弧長電弧過長時,無法保護融化后的金屬,氣體入侵熔池,容易使焊縫出現氣孔,進而導致焊縫力學性能降低,無法通過檢驗,需要進行返工重焊。電弧過短時,會增加對母材表面的壓力,受推力的影響,融化的金屬難以成形。

      (五)焊道層數減少焊道層數,增加單層厚度,在焊接過程中熔池溫度就會太高,不利于保障焊縫金屬的塑性,且焊渣在焊接過程中翻轉,會造成未熔合和夾渣等缺陷。如果增加焊道層數,減小單層厚度,有利于提高焊縫質量,但會降低焊接效率。

      (六)焊工水平在焊接焊縫時,一些焊工缺乏焊接技術,對手工電弧焊掌握不夠,很容易引起焊接質量問題。比如,在進行手工電弧焊時,焊條角度、運條方式、收弧等操作控制不當,都會嚴重影響焊接質量。

      (七)其他方面焊前未清理干凈坡口上的銹、油和水分等,容易造成焊接過程中出現夾雜、氣孔等缺陷。對口間隙太大,會造成焊瘤;對口間隙太小,會造成焊縫根部焊不透。焊接時防風措施不到位,會增加焊縫的氣孔。焊接過程中使用的焊條未烘干,或焊條未使用保溫桶等因素,會導致焊縫成型不好,焊縫的氣孔增多,導致焊縫質量不能達標。

      二、焊接缺陷的預防策略

      (一)做好焊前準備在焊接之前,首先要進行焊機試焊,調節好電流,確保焊機的電弧推力正常。其次要注意檢查電氣設備、操作機構、冷卻系統、氣路系統及機體外殼有無漏電。焊機送絲機構應定期潤滑。還要注意電焊機使用環境的安全,準備好工作人員佩戴的焊接工作服、安全帽和護目鏡,避免發生意外。

      (二)制作焊接坡口焊接時要制作合理的焊接坡口,根據焊件的厚度制作坡口,可制作雙V坡口、V型坡口和U型坡口等,坡口的邊緣控制在20毫米之內,鈍邊尺寸控制在1至2毫米之間,使用磨光機進行打磨,直至透出金屬光澤,把表面的油污、鐵銹等都清理干凈。

      (三)提前預熱處理對于厚壁高強度鋼的焊接,在焊接之前一定要先進行預熱處理,預熱的寬度從焊縫的邊緣起開始計算,每一側都要大于焊件厚度的4倍,同時要確保在100毫米以上。在預熱方法的選擇上,可以利用柔性的陶瓷電阻加熱器進行預熱,也可以直接使用火焰進行預熱。

      (四)規范焊接操作打底焊接的關鍵是控制好收弧、起弧及接頭的質量。在起弧時要適度增大電壓,收弧時要填滿熔池。結束打底后,馬上自檢,在檢查完根層焊縫后,要立刻焊接次層焊縫,以杜絕出現裂紋。在焊接多道多層時,要逐層檢查,合格后才可焊接下一層。重要焊縫焊接要使用堿性焊條。其中,第一層和蓋面的焊接,可選擇直徑3.2毫米的焊條,中間層可選擇直徑4毫米的焊條。焊接前,在350攝氏度下烘干焊條1至2小時。在使用過程中,將焊條放置于接電的保溫桶內加熱。在室外存放焊條的時間要在4個小時之內,重復干燥焊條的次數不要超于2次。

      (五)合理控制焊接參數要結合母材的壁厚、材質、焊條直徑和焊接位置選擇焊接電流,保證焊接時的電流不會造成焊瘤、焊縫咬、未熔透及夾渣等缺陷。焊接時最好選擇短弧焊接,有效保護熔池,以防侵入空氣而導致氣孔等缺陷。適當掌握焊接速度,既不能太慢也不能太快,氬弧焊每層厚度掌握在3至4毫米之間,焊條電弧焊的單層厚度最大不得超過焊條直徑2毫米。要減少高溫停留時間,降低對焊縫力學性能的影響。為杜絕出現冷裂紋,要根據有關要求,采取焊口預熱、焊后緩冷等措施。

      (六)提高焊工焊接技能焊工的技術水平直接影響到焊縫的焊接質量,加強對焊工的技能培訓是提升焊接質量的關鍵。因此,要定期組織焊工進行業務技能的學習與培訓,并且要注重理論聯系實際,最好是以師帶徒的形式,進行“一對一”的手把手指導,快速提高焊工的焊接技術水平。在進行焊接操作之前,焊接施工人員必須取得焊工上崗資格證,且上崗操作前一定要開展有關項目的仿型考試,經考試合格后才可上崗操作。

      三、結語

      總而言之,對焊接質量造成影響的因素較為復雜,不但有人的因素,也有外界條件的因素,因此,在焊接過程中要嚴格加強過程控制,創造良好的焊接條件,盡量減少和避免焊接缺陷,以促進焊接質量的提升。

      參考文獻:

      [1]顏兵強.焊接缺陷成因及防治措施[J].建筑與裝飾,2016(12).

      [2]徐銳,魏習.道岔鋁熱焊質量控制及缺陷原因分析[J].建筑工程技術與設計,2014(02).

      [3]張淑清.鍋爐焊接缺陷的成因分析及應對措施探討[J].南方企業家,2018(04).

      [4]馮軼.超大型鑄鋼件安裝焊接施工技術[J].浙江建筑,2018(09).

      [5]路程,鐘紅春,汪永勝,等.大型超厚G20Mn5鑄鋼件異種鋼焊接施工技術[J].焊接技術,2015(03).

      焊接方向刊物推薦:《焊接技術》雜志是由天津市焊接研究所與中國工程建設焊接協會聯合主辦,國內外公開發行的介紹焊接設備、工藝、材料等內容的專業期刊。1993年和1995年《焊接技術》雜志兩次入選國家中文核心期刊,并被選為金屬學、金屬工藝學科的核心期刊;于1997年榮獲全國第二屆優秀科技期刊三等獎。

      

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