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内聚连接到钢时，目前不可避免地使用焊剂。所使用的焊剂不仅有害，而且还会在连接中导致不可忽略且通常不可完全预测的孔隙率，这会显著影响结合强度，这取决于它们的尺寸和分布。通过超声波在液态焊料中产生空化来替代焊剂似乎是一种很有前途的解决方案。该项目的目的是开发一种用于硬质合金与钢的无焊剂连接的超声辅助焊接工艺。与其他接头的初步工作已经表明强度增加了1.5倍。结果表明，硬质合金的成分可以溶解并进入液体焊料。因此，有必要检查关于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，应开发适当的工艺控制，以最大限度地减少硬金属在钎焊过程中的影响，但仍导致无孔材料。先前考虑的材料要么具有很强的抗氧化性（蓝宝石或SiC），要么由于低的起球Bedworth比，形成非常薄的钝化层（Al，Ti合金），其被空化破坏。在这方面，必须考虑钢的氧化行为或氧化皮行为。特别是在高工艺温度下，钢倾向于形成坚固的、不腐烂的氧化物。与目前的技术水平相比，这是该研究项目最大的挑战之一。有必要分析各种类型钢在热处理和钎焊过程中的氧化行为。此外，需要澄清的是，在多大程度上，超声波的应用以及由此产生的机械渗透和空化可以激活表面并将其从现有的氧化物中去除。