通用汽車公司即將推出一種新型革命性制造工藝，可將鋼材點(diǎn)焊至鋁制材料。據(jù)了解，這種專利工藝將首先應(yīng)用至公司位于密歇根州哈姆特拉米克市的裝配廠。由于采用了這種先進(jìn)鋼-鋁異種材料點(diǎn)焊工藝，通用汽車在為凱迪拉克CT6生產(chǎn)座椅椅背部件時，并不需要再使用鉚釘連接鋁制支架和鋼制框架。
工程師聲稱，通用汽車的鋼-鋁焊接工藝將于今年晚些時候問世，屬業(yè)界首創(chuàng)。如果在椅背上的應(yīng)用步入正軌，通用汽車計劃將這種鋼-鋁點(diǎn)焊工藝的應(yīng)用范圍擴(kuò)大至CT6旗艦轎車的發(fā)動機(jī)蓋。目前，這款CT6轎車是通用汽車在“多種材料應(yīng)用”方面最為大膽激進(jìn)的車型。
公司研發(fā)部輕質(zhì)材料加工實驗室部門經(jīng)理Blair Carlson表示，新工藝的焊槍尖端采用了一種經(jīng)過專門設(shè)計的脊?fàn)铍姌O，這對整個點(diǎn)焊系統(tǒng)非常關(guān)鍵。總體來說，通用汽車的創(chuàng)新鋼-鋁異種材料點(diǎn)焊工藝共擁有19項硬件和控制方面的專利。
具體來說，這種先進(jìn)的脊?fàn)铍姌O有助于改善現(xiàn)有點(diǎn)焊電極的物理屬性，比如點(diǎn)焊兩種材料時的熔點(diǎn)僅為900ºC左右、因鋁制元件的氧化而影響焊接的完整性，以及更容易在兩種不同材料之間形成一種“玻璃”層，從而使焊接更加脆弱，這些屬性均會影響鋼-鋁異種材料的焊接效果。
Carlson表示，現(xiàn)有噴槍的噴嘴基本上每焊20下就需要新涂層，而我們的目標(biāo)是將這個周期提高至以“百”為單位。通用的研究部門正在積極研究新的焊接工藝，從而控制成本增加、提高裝配廠組裝混合材料汽車時的工具靈活度，并最終讓鋼-鋁異種材料焊接完全擺脫鉚釘。
一旦在凱迪拉克CT6座椅靠背部件中的應(yīng)用步入正軌，通用的工程師開始計劃將這種先進(jìn)異種材料焊接工藝的應(yīng)用范圍擴(kuò)展至發(fā)動機(jī)蓋中，具體是利用這種工藝將鋼制行人防撞杠焊在鋁制發(fā)動機(jī)蓋“里面”。Carlson表示，新工藝將協(xié)助公司去除目前用來連接這兩個部件的鉚釘。
凱迪拉克CT6在混合材料應(yīng)用上非常大膽，整個車身結(jié)構(gòu)共采用了11種不同的材料。憑借公司的先進(jìn)連接技術(shù)，這款旗艦轎車的裝配已經(jīng)累計去除了超過1400個鉚釘，從而實現(xiàn)了控制重量與成本的目的。通用汽車公司估計，新的焊接工藝可以協(xié)助公司部分車型去除重約10磅（4.5公斤）的鉚釘。
雙光束激光
在一場媒體活動中，通用汽車宣布即將推出這種先進(jìn)的鋼-鋁異種材料點(diǎn)焊工藝。此外，通用的工程師還同時介紹了公司其他現(xiàn)有高級連接技術(shù)目前的情況，其中包括公司的增強(qiáng)版鋁-鋁激光焊接技術(shù)，以及一種新型雙光束激光焊接技術(shù)。這種雙光束激光焊接可以提供更好的表面處理效果，而且并不需要像過去一樣清理飛濺的焊渣。
此外，通用汽車還優(yōu)化了一款孔徑板。經(jīng)過重新設(shè)計的孔徑板可以更好地控制激光焊機(jī)的反射。Carlson表示，過去的孔徑板焊接30輛車后就必須更換，而升級后的孔徑板已經(jīng)服務(wù)了超過3000輛車，現(xiàn)在仍在使用，而且由于新的孔徑板僅僅是優(yōu)化了形狀，因此幾乎并未增加任何成本。
通用汽車在總結(jié)公司最近的整車減重表現(xiàn)時表示，由于采用了輕質(zhì)技術(shù)，公司最近推出的7款車型共減重2480磅（1125公斤），其中2017款GMC Acadia減重700磅（318千克）、2016款雪佛蘭（Chevrolet）Camaro減重400磅（181公斤）。根據(jù)通用工程師的估算，這些減掉的重量相當(dāng)于可以減少13.7萬公噸的二氧化碳排放。
作者：Bill Visnic
來源：SAE汽車工程雜志
翻譯：SAE 中國辦公室
GM prepping industry-first steel-to-aluminum welding process
General Motors is poised to pull the trigger on a potentially game-changing manufacturing process to spot weld steel to aluminum. In the first production application for the patented process at GM’s Hamtramck, MI, assembly plant, the advanced spot welding eliminates rivets that join an aluminum bracket to a steel framework to form part of the seatback for the Cadillac CT6.
Engineers claim GM’s steel-to-aluminum welding will be an industry first when it launches later this year. If all goes according to plan with the seatback frame, GM intends to expand the process to the hood of the CT6, a new flagship sedan that currently represents the company’s most aggressive use of multi-material construction.
A specially-designed ridged electrode for the welding-gun tip is a key component of the system, said Blair Carlson, lightweight material processing lab group manager at GM Research & Development. In all, there are 19 patents covering hardware and controls for the process.
The advanced electrode helps to alleviate the physical-properties issues that to now have stymied steel-to-aluminum welding, including the 900º C delta in melting points between the two materials, formation of oxides on the aluminum component that compromise weld integrity and the tendency for a “glassy” layer to form between the two disparate materials, causing brittleness of the weld.
Carlson said cycle time before the welding-gun tip requires dressing currently is about 20 welds. The goal is to move the cycle into the hundreds—this as part of the GM research unit’s mandate for the new welding process to minimize added cost, enhance assembly-plant tooling flexibility for mixed-material vehicles and eventually eliminate altogether the need to rivet steel and aluminum.
Once the mixed-material welding of the CT6 seatback is up to speed, engineers are eying the car’s hood with the intention of welding the pedestrian-impact steel reinforcement to the hood's aluminum “inner.” This will eliminate scores of rivets currently used to join the two pieces, Carlson said.
Advanced joining techniques for the CT6, which employs 11 different materials in the body structure, already have eliminated more than 1400 rivets, which in aggregate add incremental weight and cost. GM estimates the new welding process could eliminate up to 10 lb (4.5 kg) of rivets on some vehicles.
Dual-beam lasers
The news of GM’s imminent deployment of the steel-to-aluminum spot-welding process came at a media event at which engineers also provided updates of other advanced-joining techniques the company currently employs. Those include a refinement to GM's aluminum-to-aluminum laser welding and a new, dual-beam laser that reduces weld spatter, providing a better overall surface finish and eliminating a process formerly required to clean the spatter from the surface.
Another improvement: a redesigned aperture plate that controls reflection on the laser welder. The previous aperture plate had to be replaced after 30 vehicles moved through the body shop. With a more-optimized shape that came at almost no cost, the upgraded aperture plate has been used for more than 3000 vehicles and remains in service, Carlson said.
Summarizing recent whole-vehicle weight reductions, GM said that for seven recently introduced models, lightweighting measures have chopped a total of 2480 lb (1125 kg), including a 700-lb (318 kg) reduction for the 2017 GMC Acadia and 400 lb (181 kg) for the 2016 Chevrolet Camaro. The aggregate savings delivers a CO2-equivalent reduction of 137,000 metric tons, GM engineers calculated.
Author: Bill Visnic
Source SAE Automotive Engineering Magazine
目前，凱迪拉克CT6座椅靠背中的一些部件（正面的小型部件）率先采用了通用汽車的業(yè)界首創(chuàng)鋼-鋁異種材料點(diǎn)焊工藝。一旦技術(shù)應(yīng)用步入正軌，通用汽車會將這種工藝的應(yīng)用拓展至CT6的發(fā)動機(jī)罩。
通用汽車估計，公司最近推出的7款再設(shè)計版車型與之前版本相比，共可實現(xiàn)減重2480磅。