Development of an ultrasonic-assisted brazing process for fluxless joining of cemented carbides to steel

开发用于硬质合金与钢的无焊剂连接的超声波辅助钎焊工艺

• 批准号: 398973434
• 负责人: Professor Dr.-Ing. Wolfgang Tillmann
• 金额: --
• 依托单位: Lehrstuhl für Werkstofftechnologie (LWT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/398973434?language=en
• 关键词: Development; ultrasonic; assisted; brazing; process

When cohesively joining carbide to steel by means of brazing technology, the use of fluxes is currently, inevitable. The fluxes that are used are not only harmful, but also cause a not negligible and usually not completely predictable porosity in the joining, which significantly affects the strength of the bond, depending on their sizes and distribution. A substitution of the flux by generating cavitation in the liquid solder by means of ultrasonic waves seems a promising solution.The aim of the project is to develop an ultrasound-assisted soldering process for a flux-free joining of carbide to steel. Preliminary works with other joints already showed an increase of the strength by 1.5 times. It was revealed that constituents of the cemented carbide can dissolve and get into the liquid solder. It is therefore necessary to examine the process control concerning how far the mechanical properties of brittle carbides and the resulting joint are affected by the penetration of the ultrasound. Furthermore, a suitable process control should be developed that minimizes the impact of the hard metal during brazing, yet results in a non-porous material. Materials that were previously considered either had a strong resistance to oxidation (sapphire or SiC) or, due to a low pilling Bedworth ratio, formed a very thin passivation layer of (Al, Ti alloys), which are broken up by cavitation. In this regard, the oxidation behaviour or scale behavior of steel must be taken into account. Especially at high process temperatures, steel tends to a strong, non-decaying oxide formation. Compared to the current state of technology, this is one of the biggest challenges of this research project. It is necessary to analyze the oxidation behavior of various types of steel during heat treatments and brazing. Furthermore, it needs to be clarified as in how far the application of ultrasound alongside the resulting mechanical penetration and the cavitations can activate the surfaces and rid it from existing oxides.

当通过钎焊技术将碳化物粘合到钢上时，目前不可避免地需要使用焊剂。所使用的助焊剂不仅有害，而且还会在连接处产生不可忽略且通常无法完全预测的孔隙率，这会显着影响粘合强度，具体取决于其尺寸和分布。通过超声波在液体焊料中产生空化来替代助焊剂似乎是一个有前途的解决方案。该项目的目的是开发一种超声波辅助焊接工艺，用于硬质合金与钢的无助焊剂连接。与其他接头的初步研究表明强度增加了 1.5 倍。据透露，硬质合金的成分可以溶解并进入液体焊料中。因此，有必要检查有关脆性碳化物的机械性能和由此产生的接头受超声波穿透影响的程度的过程控制。此外，应开发合适的工艺控制，以最大限度地减少钎焊过程中硬金属的影响，同时产生无孔材料。以前认为的材料要么具有很强的抗氧化性（蓝宝石或碳化硅），要么由于起球贝德沃斯比低而形成非常薄的钝化层（铝、钛合金），该钝化层会被空化破坏。在这方面，必须考虑钢的氧化行为或氧化皮行为。特别是在高加工温度下，钢往往会形成坚固的、非腐烂的氧化物。与目前的技术水平相比，这是该研究项目面临的最大挑战之一。有必要分析各类钢在热处理和钎焊过程中的氧化行为。此外，还需要澄清超声波的应用以及由此产生的机械穿透和空化可以在多大程度上激活表面并清除现有的氧化物。