Aero Space Welding Jun 30, 2022 10:50:58 AM 15 min read

Lynn Welding's Nadcap Approved Fusion Welding Services

Lynn Welding's Fusion Welding Operations

A fusion weld is characterized by the merging of two or more materials – same or different – through the application of heat. The heat can come from a variety of means, such as gas/fuel, electricity, or laser beams. In some cases, filler material is added to the welding process and is melted down to bring about a homogeneous (as in the filler material is of the same composition/type as the base) or heterogenous (they differ in composition) weld. Not all fusion welding operations require or make use of filler material, but Lynn Welding has frequent need for them, so they are included in their Nadcap evaluation’s scope. Fusion welds that do not utilize filler material are referred to as autogenous.

To produce a fusion weld, the base materials have to be melted first and then, if applicable, the filler material should be allowed to melt and flow into the weld area. During this process, it is vital that the melting is fast but still under the welder’s control so that they can strictly monitor the weld pool forming. The welder must also have knowledge of heat affected zones (HAZ), as these too can negatively impact the integrity of the part if they are unaware or untrained in working/dealing with them. In addition, if there is too much heat generated, whether in a certain area or across multiple spots, then the part can become distorted as well.

 

The Impact of Fusion Welding Nadcap Approvals

To attain a Nadcap accreditation is to proclaim that your procedures and products are stringently maintained and measured to the highest of standards. To lose a Nadcap accreditation is therefore announcing the very opposite. Your customers will think you are sloppy, unreliable, and negligent in maintaining and managing your internal systems. There would be a significant loss to the business.

However, if we assume that the Task Group has approved the audit and corrective actions, then the company will be accredited as Nadcap approved to service the aerospace industry. This approval comes with the ability to use the Nadcap logo and name, which is likely to also attract more subscribers and customers into utilizing your business.

For Lynn Welding, this accreditation is especially vital for our business, because we provide services to the leading primes of the aerospace industry, as well as a number of military and defense ones. Our customers are especially reliant on our Nadcap accreditation as a sign that we are certifiably tested and up to the task of providing them with welding services.

The initial goal of the Nadcap audit was to ensure that there would be less of a need for primes to personally audit their suppliers, and in keeping with that, the audit has specialized, modified questions that can be asked of any supplier of a given prime. These portions of the audit are called supplemental checklists. This ensures that if a supplier is to keep their Nadcap accreditation, this is a trustworthy sign that they are up to their customer’s latest standards.

 

Welder & Inspection Qualifications 

For every inspector and welder within the company, there must be proof that they are qualified for their position and their jobs. For both positions, the company must maintain and retain documentation proving that they have passed eye exams and weld and color vision testing. For resistance, welders have to have eye exams every two years and fusion is every year. The frequency of these tests also has to be explicitly stated in a written record. There must also be documentation covering who can and cannot work on certain materials/positions.

When qualifying a welder, the person and machine have to be qualified. There are two primary documents needed for the latter portion of the process: the weld production schedule (WPS) and the procedure qualification record (PQR). These ensure that our machines are capable of producing acceptable welds and that our schedules have been tested for consistency and repeatability. The PQR can be inspection certification, test result, or an old job qualifying the WPS, so long as it is objective evidence.

For inspectors, to prove that they are qualified for their position, the company has to have records in place showcasing that they have been tested and trained to aerospace standards. For Lynn Welding, we keep training records and eye exam results for all of our staff. This ensures that no one who is colorblind or not approved for a certain material – no one colorblind can work on titanium unless they test out of it (only applicable to some specifications, not all) – ends up working on or inspecting a job that they don’t have the qualifications for.

 

Material Cleanliness

In the aerospace industry, it is vital that materials are cleaned, maintained, and controlled. This is directly reflected in the fact that nearly every audit Lynn Welding has gone through has inspected for the control of cleanliness in relation to job or part materials. Nadcap checks to verify that there is a procedure in place for not only how staff should clean the materials but also for what needs to be done if any contamination occurs. They also check for how these procedures are flowed down to the floor.

In the case of Lynn Welding, the traveler that moves through the welding process with the job contains any relevant cleaning and packaging information from the customer’s or standard specifications. Some customers require their parts to move from stage to stage with very specific, protective measures. It is necessary then to have documented proof detailing how each staff member is trained to look for and identify those requirements. The same goes for cross-contamination records; a detailed training record goes a long way during an audit to ensure that all procedures, standards, and specifications are being followed and controlled for within a company.

 

Wire Brush 

Since fusion welding often involves filler material and resources that need to be wire brushed, records need to be maintained that document the composition of the wire brushes used by the welders.

Additionally, all wire brushes should be controlled so that no welder can enter a booth, grab one of an unknown composition, and potentially contaminate a job. For this reason, the release, restocking, and labelling of the brushes are strictly accounted for at Lynn Welding and any unlabeled or untraceable materials are considered unusable.

 

Supplemental Checklists

There are such things as “supplemental” checklists. These specialized processes are ones that are specifically requested by the primes or subscribers that a company is recognized for servicing. For instance, Lynn Welding works on projects for Boeing, Bell Helicopter, Gulfstream, General Electric, Rolls Royce, and Raytheon, as well as a number of other primes, so the audit will often have an equal number of supplemental requirements to check over. The more primes the company works for, the more additional requirements – or supplemental checklists – that they will likely have to go through. Oftentimes, the prime’s checklists serve to double-check and verify that specific interests of theirs are properly reviewed and accounted for. Their checklists, just like those of the main audit, can change or alter paths.

 Titanium: Some primes may wish to double check that lint free gloves are always required when dealing with titanium parts, especially if their projects routinely utilize titanium compositions.

The use of these gloves prevents stress corrosion. If the welds were to be touched directly, the chlorines would react with the residue left behind in such a way that causes stress corrosion cracking, which would result in the failure of that weld. Therefore, a subscriber who uses a lot of titanium may want to require that the use of gloves is properly regulated and controlled for in their suppliers. To document control for this, Lynn Welding has explicit directions on every job’s traveler and markings that travel with the parts throughout the welding process, as well as training records to attest to the competency of the staff who work with titanium.

Filler material: An OEM that uses very valuable or high-dollar material compositions may wish to confirm that all filler material used is strictly maintained. So, they may require the auditor to check how weld wires are stored, labelled, cleaned, and disposed of. A company such as Lynn Welding would then have to prove to the auditor that the weld wire is locked away, that only authorized personnel have access, and that the “authorized” person has the training or certifications necessary for that responsibility.  

wire itself is of an appropriately assessed and documented composition. In this case, the quality team should have well-kept records documenting the certifications, proving the compositions and suppliers of their wires are reliably accounted for.

Gas: A prime who primarily relies on gas fusion welding may want to verify that their suppliers have a system in place that retains all certifications of conformance (CoC). The CoC may not be enough for them though so the certification of analysis (CoA), which costs a bit extra, and details exactly what is in the gas, may also be required by them. Again, these records should be maintained by the quality team and held onto for a time frame specified by either customer or standard specifications.

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