Ford Spot Weld Spec

Engineering Specification

Frame 2 of 12 Revised 9.12.2002 EBIW E 11446533 000 ES-1S71-1K251-AC

This copy is uncontrolled – the original resides in SPEED at http://www.speed.ford.com/

SCOPE: This specification defines the requirements of spot welds used in the fabrication of assemblies comprising two or more thickness of steel of the same or different gauge.

It is additional information of resistance spot welds on drawings or defined by CAD Data. The definition excludes items, which are already described in Ford Engineering CAD & Drafting Standards and/or Manufacturing Standards (U-WX 012).

APPLICATION: This Engineering Specification applies to steel sheet, strip or plate in the uncoated condition and

also with coatings of zinc, tin, nickel, terne alloy (tin & lead). It also applies to steel coated with temporary coatings for rust prevention and paint primers providing the coating does not effectively interfere with the welding process.

It applies to the following categories of steels:

CATEGORY TYPE OF STEELS

FORD MATERIAL SPECIFICATION No.

Category A Mild Steels, Hot & Cold Rolled, Low Carbon

WSS-M1A344-A1/A2 WSS-M1A345-A1/A2/A3/A4

Category B High Strength Low Alloy Steels

WSS-M1A346-A1/A2/A3 WSS-M1A347-A1/A2/A3

Category C Dual Phase Steels WSS-M1A348-A1/A2/A3/A4/A5/A6/A7

The text of the referenced Ford Material Specifications is available from the following weblink http://www.mats.ford.com/mats/scripts/spec_by_mtlCat.html, Metals 1A-99A.

1. WELD IDENTIFICATION The weld symbols shall be in accordance with Ford Engineering CAD and Drafting Standard D-3 (Welding Symbols And Specifications) as outlined in the Cadmethods weblink http://www.cadmethods.ford.com/cad_methods/welding/weld_namnum_eu.html.

2. DEFINITIONS

2.1 Button

Figure 2.1 shows a button that is pulled out of one of the welded components as the result of a chisel (peel) test as described in Section 7.4. A button typically occurs in those cases where the chisel tests leads to either a peel fracture or a combination fracture as shown in Figure 2.2 below.

Figure 2.1: Button As A Result Of A Peel Test




2.2. Button Diameter dp

In the cases of a peel fracture and a combination fracture, the button diameter dp is the average of two diameters measured at right angles to each other when one of the diameters is the apparent minimum. See Figure 2.2, sections a) and c) for a detailed illustration.

Figure 2.2: Button & Fracture Face Diameters dp 2.3 Shear Fracture Face

• Category A- and B-Steels A shear fracture typically occurs in the case of different gauge combinations and on larger spot

welds.

• Category C-Steels A shear fracture may also occur on joints made of Category C-sheet steel combinations due to the

metallurgical changes in the metal during the welding process.

Figure 2.2, Section b) illustrates a typical shear fracture face. It is characterized by a lack of a button. The occurrence of the shear fracture is acceptable provided that there is evidence of good metal adhesion at the weld i.e. the fracture face is crystalline and there is metal distortion in the parent metal around the weld. The shear fracture face diameter (also indexed as dp) is the average diameter of the fractured surface without the adhesion zone (also called “ring zone” as shown in Figure 2.2, Section b)). 2.4 Nugget

The nugget is the fused metal forming the weld. It is visible in a section cut only.

Figure 2.4: Weld Nugget




2.5 Weld Penetration p

The weld penetration p is the depth of the nugget in any one sheet, strip or plate compared with the thickness of that sheet, strip or plate. Figure 2.5 shows the scheme of a nugget in a section cut exemplary for a 2-gauge combination.

Figure 2.5: Weld Penetration And Nugget Diameter The acceptance criteria for the weld penetration p are as follows:

• 2 - Sheet Combinations: 8.04.01

1 ≤≤tp

and 8.04.02

2 ≤≤tp

• 3 - Sheet Combinations: 8.03.01

1 ≤≤tp

and 8.03.02

2 ≤≤tp

and 8.03.03

3 ≤≤tp

2.6 Nugget Diameter dL

The nugget diameter dL in a section cut as shown in Figure 2.5 shall comply with the following requirements:

Thickness Of Thinner Sheet

[mm]

Minimum NUGGET DIAMETER dL

as shown in Figure 2.5 [mm]

0.5 - 0.79 3.1 0.8 - 0,99 3.5 1.0 - 1.24 3.9 1.25 -1.59 4.4 1.60 - 1.99 4.9 2.0 - 2.49 5.5 2.5 - 3.14 6.2

3.15 - 3.54 7.0 3.55 - 3.99 7.4 4.0 - 4.49 7.8 4.5 - 4.99 8.3 5.0 - 5.59 8.7 5.6 - 6.0 9.2

Table 2.6: Minimum Nugget Diameter dL 2.7 Sheet Metal Thickness

Sheet metal thickness as referred to in Table 6.2.

dL

t2

p1

t1

p2

-

Nugget

Ring Zone




2.8. “Weld Joint”

A “Weld Joint” (weld-line) is defined as all of the welds that weld a specific set of parts which creates a structural unit for providing the specified body strength. (Ref: http://www.be.ford.com/avt213/procs/03063/weld_strategy.htm)

3. WELD HARDNESS

3.1 Category A- and B- Steels The material used and the welding techniques employed shall be such that the hardness of the weld shall not exceed HV 400.

3.2 Category C- Steels The material used and the welding techniques employed shall be such that the hardness of the weld shall not exceed HV 460. 4. DISTANCE BETWEEN WELDS

The pitch of the welds shall be considered to be the distance between centres of adjacent spot welds. For spot welds set with automatic welding machines the general tolerance on the pitch is + 10% (unless otherwise specified). The general tolerance on pitch for manual spot welds is - 40% and the excess number of spot welds allowable, related to this tolerance, is 20 %. The minimum distance of spot welds is defined in the manufacturing standard U-WX 012.

5. DISTANCE FROM EDGES & FLANGES

The centers of the spot welds shall be in the middle of the flange. The tolerance will be such that the edge of the weld shall be at least 1/2 dp away from the edge or

the flange radius (dp = button or fracture face diameter as specified in Table 6.2 below). The minimum flange overlap is defined in the manufacturing standard U-WX 012.

Figure 5: Distance From Edges & Flanges

min dp / 2

dp




6. WELD PROPERTIES & QUALITY 6.1 Button Size

The weld size as specified on the drawing, in the CAD Data file, or in Table 6.2 of this specification, shall refer to the button or fracture face diameters dp which are revealed as a result of the chisel test described in Section 7.4. The acceptance criteria for this test are shown in Table 6.2 as it lists the minimum button or fracture face diameter dp relative to the thickness of the thinner sheet of the combination.

6.2 Shear Strength

Static tensile testing shall be performed in accordance with DIN EN ISO 14273 to determine spot weld shear strength.

6.2.1 Category A- and B-Steels & Their Combinations

Category A- and B-steels and their combinations have been analyzed in generic tensile testing with regards to shear strength. The welds shall have the guaranteed minimum shear strength values given in Table 6.2 below. This table applies to uncoated and zinc-coated material only.

Thickness of Thinner Sheet

[mm]

Minimum BUTTON or FRACTURE

FACE DIAMETER dp as defined in

Sections 2.2 and 2.3 [mm]

Minimum Shear Strength

[kN]

0.5 - 0.79 3.6 2.5 0.8 - 0,99 4.0 3.2 1.0 - 1.24 4.5 4.0 1.25 -1.59 5.0 5.0 1.60 – 1.99 5.6 6.3 2.0 - 2.49 6.3 8.0 2.5 - 3.14 7.1 11.2

3.15 – 3.54 8.0 16.0 3.55 – 3.99 8.5 19.0 4.0 - 4.49 9.0 22.4 4.5 - 4.99 9.5 26.5 5.0 - 5.59 10.0 31.5 5.6 – 6.0 10.6 35.5

Table 6.2: Minimum Button Or Fracture Face Diameter dp And Shear Strength For Category And B Steels And Their Combinations (dp˜ 1.15*dL)

6.2.2 Combinations Involving Category C- Steels

Combinations involving Category C-steels shall comply with the minimum button or fracture diameter requirements as outlined in Table 6.2 above. 6.3 Weld Defects

6.3.1 All Combinations Of Steel Categories With The Exception Of B-C, C-C

The fracture surface of the button or fracture faces shall be metallic bright and free from evidence of hot cracking. A weld shall be classed as defective if it shows any evidence of burn through or porosity. No cracks are allowed in any part of the weld.




6.3.2 Combinations Of Steel Categories B-C And C-C

The fracture surface of the button or fracture faces shall be metallic bright and free from evidence of hot cracking. A weld shall be classified as defective if it shows any evidence of burn through or porosity.

Acceptance Criteria For Weld Defects

Minor cracks and inclusions may occur in combinations of High Strength Low Alloy Steels (Category B) with Dual Phase Steels (Category C). Joints made of Dual Phase Steel combinations (Category C-C) are also likely to a show minor occurrence of cracks and inclusions. These weld defects are only detectable in micro-section cuts that shall be performed as part of the pre-production welding trials.

During these trials, the acceptance criteria for the weld defect occurrence shall be as follows:

• Cracks The overall length of one or several cracks shall not exceed 15 % of the nugget diameter dL in a micro-section cut.

• Inclusions The overall length of one or several inclusions shall not exceed 15 % of the nugget diameter dL in a micro-section cut.

• Combined Effect Of Cracks & Inclusions

The overall length of cracks and inclusions shall not exceed 15 % of the button diameter dL in a micro-section cut. 7. PRODUCTION VALIDATION & IN-PROCESS TEST REQUIREMENTS 7.1 Definition Of Production Validation (PV) & In-Process (IP) Tests

Production Validation (PV) tests are used to obtain an initial estimate of the process potential to produce parts that conform to engineering requirements, and to identify causal or predictive relationships between significant design and process characteristics (to be used for process control). The tests must be completed successfully using initial parts from production tooling and production process before Part Submission Warrant (PSW) approval and authorization of production parts can be issued. Sampling plans for PV testing must be included in the control plan. In-Process (IP) tests are used to further understand the relationship between significant design and process characteristics and to establish a basis for continuing improvement. Tests must be completed with production parts on an ongoing basis. Sampling plans for both IP testing and evaluation of the significant process characteristics must be included in the Control Plan. When the process is found to be out of control or the test acceptance criteria are not met, the reaction plan approved in the Control Plan shall be invoked. Note:

The table that follows summarizes the various PV- and IP-tests and specifies their respective applicability. Some tests are specified as mandatory tests (e.g. Visual Inspection). Recommendations are issued in the case that multiple test choices exist (e.g. in the field of In- Process Control). The ultimate test method shall then be selected on the basis of an individual risk and test method capability assessment during PV-phase.




Summary Of Production Validation (PV) & In-Process (IP) Tests

Test No.

Test PV, IP Applicability / Limitations

7.2 Visual Inspection PV, IP Mandatory inspection for PV & IP-testing; Visual inspection must be complemented by one of the following tests: 7.4 (Destructive Chisel Test), 7.5 (Non-Destructive Chisel Test) or 7.6 (Ultrasonic Inspection)

7.3 Macro-/Micro- Section Cuts

PV Shall be conducted during PV-testing as a method for concern root cause analysis

7.4 Destructive Chisel Test

PV, IP Shall be conducted during PV-testing to determine compliance with the min. button/ fracture face diameter requirements as listed in Table 6.2; IP-testing: Alternative test procedure in case that neither 7.5 (Non-Destructive Chisel Test) nor 7.6 (Ultrasonic Testing) can be applied (risk & capability assessment)

7.5 Non-Destructive Chisel Test

IP It is applicable for IP-testing only. Note: this test procedure – in contrast to 7.4 (Destructive Chisel Test) - is not suitable to verify compliance with the min. nugget /fracture face diameter requirements. Limitations: It applies to steel sheet having a gauge = 1.5 mm and/or Category A & B steels with a yield strength less than 260 MPa only - with the following exceptions:

• sheet steel with a hot dip galvanized coating,

• joints with functional flanges (e.g. door opening flange carrying the sealing)

• weld-bonded joints • joints on Class 1surfaces

7.6 Ultrasonic

Inspection Capability & Correlation Tests

PV Shall be performed during PV-testing alongside 7.3 (Macro-/Micro- Section Cuts) and 7.4 (Destructive Chisel Test) in the case that ultrasonic testing is considered to be the suitable test method for IP-testing

Ultrasonic Inspection

IP Recommended test procedure for IP-testing

Table 7.1: Summary Of Production Validation (PV) & In-Process (IP) Tests 7.2 Visual Inspection

Visual inspection is performed to detect obvious defects such as surface cracks, surface pores, increased indentation, burn damage and spatter.

7.3 Macroscopic Inspection, Micro-Section Cut

A macroscopic examination at a magnification of 10 - 20 times at the weld surface, or a microscopic examination on a section through the welds (polished specimen) should be conducted in cases of doubt.




7.4 Destructive Chisel Test

In this test, a tapered drift pin (or equivalent) is used to apply a peeling action between spotwelds without cutting of the sheet metal or weld nugget at the interface. 7.5 Non-Destructive Chisel Test

In this test, a pry bar should be located near or between the spot welds. The pry bar shall be driven without cutting sheet metal or weld until the metal adjacent to the weld is distorted. Welds that hold will be classified as satisfactory welds. Welds that unintentionally pull buttons or fracture face diameters equal to or larger than the minimum size defined in Table 6.2 shall also be classified as satisfactory welds. Welds that fail without producing significant distortion of the surrounding metal shall be classified as defective welds.

7.6 Ultrasonic Testing, Inspection Capability & Correlation Tests

Ultrasonic testing is the recommended test method in the case of Category A- and B- steels having a gauge > 1.5 mm, Category C-steels and steel sheets with a hot dip galvanized coating.

Ultrasonic inspection capability and correlation shall be determined for individual joints during production validation testing in conjunction with 7.3 and 7.4.

8. WELD EFFECTIVENESS AND TOLERANCE

8.1 Control Welds

Control welds are individual spot welds or groups of spot welds that are significantly important for the structural integrity of the vehicle. As such they must be processed for optimum weld integrity and maximum effectiveness (see Section 8.3.2).

Control welds shall be identified jointly between Body Engineering (Core & Vehicle Program) and the Attribute Teams (Crash, Durability and - if applicable – NVH) on the basis of the relevant Design-FMEAs, CAE-analysis and physical verification testing.

Control welds are identified by the word ’Control’ attached to specific spot welds in the Metaphase data file. More information relative to the identification of control welds in I-DEAs can be obtained from Section 5.3.6 of the following Ford Intranet web-link: (Ref: http://www.cadmethods.ford.com/cad_methods/welding/weld_namnum_eu.html,.

8.2 Satisfactory Welds

Those welds tested and found to be satisfactory to the requirements of this specification.

8.3 Tolerance:

8.3.1 General Tolerance

The general tolerance for all Common Welds on the whole body shall be a minimum acceptance of 80 % “Satisfactory Welds”. The same tolerance applies to any weld joint on a vehicle (see Section 2.8 for the definition of a weld joint). Specific requirements apply to groups of 1 to 9 spot welds as outlined in Table 8.3 below.




8.3.2 Tolerance For Control Welds

Tolerance for Control Welds shall be a minimum of 90 % “Satisfactory Welds”. Specific requirements apply to groups of 1 to 9 spot welds as outlined in Table 8.3 below.

Common Welds Control Welds

Number Of Common / Control Spot Welds In A

Weld Joint

Missing Welds

Undersized Welds )*1

Missing Welds

Undersized Welds )*1

1 - - - - 2 - 1 - - 3 - 1 - - 4 1 - - 1 5 1 - - 1 6 1 - - 1 7 1 1 1 - 8 2 - 1 1 9 2 - 1 1

)*1 The diameter of an undersized spot weld button must be minimum 50 % of the button or fracture face diameter specified as “dp” in Table 6.2.

Table 8.3: Number Of Common / Control Welds In A Weld Joint 8.4 Defective Welds

Those welds which fail to meet any one or more of the requirements of this specification are classified as defective welds (see Table 8.3). Missing welds are also classified as defective welds. Defective welds will have to be corrected in accordance with appendix A under consideration of tolerances mentioned in Section 8.3.

8.5 Crucial Welds

The following welds are classified as Crucial Welds:

• Welds that are adjacent. • Welds that are separated by only one satisfactory spot weld. • Welds that are common to two lines of welds at their intersection. • Welds at the extremities of a line of welds (first and last spot of a joint).

Crucial Welds need to be reworked in any case - irrespective of the class and tolerance. Rework shall be performed according to the components specific repair standard or – if no specific repair standard exists – according to appendix A of this Engineering Specification. 9. WELD FINISH The surface appearances after spot welding are classified into the following categories

The class of finish and the actual surface of the component will be identified on the drawing, or in the CAD Data file, and applies to the visible side if not otherwise specified. On surfaces where no class of finish is specified, class 3 finish applies.

9.1 Class 1-Finish

This weld finish classification covers sheet metal surfaces that must be free from surface markings or imperfections after metal finishing to the extent that they are not apparent after painting and within the limits as described below. Class 1 welds for subsequent metal finish to a class 1 metal surface should be held to the least possible marking on the surface to be metal finished. Weld marking must not exceed a depth such as can be removed by metal finishing.




Metal finishing shall not remove more than 10 % of the surface thickness, or marking on excess of 10 % of surface sheet thickness must be filled prior to metal finishing. No surface expulsion of metal will be acceptable:

Welds on hemmed flanges or doors - decks - hood - glove box doors - tailgates which are specified Class 1 will be governed by the following exceptions:

Satisfactory welds will have a minimum slug diameter of 2.5 mm. Slug will be pulled from either the inner panel or turned over flange. Fusion between inner panel and surface sheet is not required. 9.2 Class 2-Finish

This weld finish classification covers a minimal marked welded surface and shall be used where a minimum amount of metal displacement is acceptable (a max. 10 % above and a max 15 % below normal surface). Surface expulsion (weld whiskers) will not be acceptable. .

Outside surface sheet metal assemblies in which Class 2 welds are required, will be governed by approved “specific” visual samples. “Outside Surface Sheet Metals” are defined as those surfaces that are visible from the outside of the vehicle in its normal running condition.

9.3 Class 3-Finish

9.3.1 Category A- and B-Steels & Their Combinations

The surface indentation shall not exceed 25 % of the specified thickness of that sheet. Where metal expulsion or displacement of the metal above the normal surface is unacceptable for safety, appearance, fit or other reasons on a general finish class of weld, the assembly drawing, or CAD Data shall specify “flash free” for each weld of this type. This will require that any excess metal so formed above the surface is removed.

9.3.2 Combinations Involving Category C-Steels

Sheet metal combinations involving Category C-steels are sensitive to joint gap related effects of indentation, specifically in combinations with Category A- and B-steels. The acceptance criteria for the indentation in joints involving Category C-steels are as follows:

Ø Scenario A: Part Matching Stays Within Common Production Tolerances. In this case, the same acceptance criteria as outlined in Section 9.3.1 apply.

Ø Scenario B: Part Matching Exceeds Common Production Tolerances In this case, deviations from the acceptance criteria outlined in Section 9.3.1 can be granted on a case-by-case basis in a joint effort of Body & Manufacturing Engineering as well as Craftsmanship. In any case, the indentation should not exceed 40% of the thickness of the thinnest sheet.




APPENDIX A:

REPAIR OF DEFECTIVE SPOT WELDS:

Spot welds which do not meet the requirements in clauses 8.1 - 8.5 must be repaired by one of the following methods, agreed by Product Development Engineering. The preferred method will be method “A“. Specific permission must be obtained to use other methods but agreements may be made to cover general situations.

A. Resistance Spot Welding

Additional effective spot weld placed as near as possible halfway between the existing spot welds.

B. Plug Welding

A plug weld may be used as a repair for a single spot weld or two plug welds for two adjacent spot welds. A plug weld involves drilling a hole in the top component which is filled by fusion welding, preferable MIG or MAG. Only two thicknesses may be permitted to be repaired.

C. Shielded Arc Spot Welding

A single shielded arc spot weld may be used as a repair for a single spot weld, or two shielded Arc spots may be used for two adjacent defective spot welds. Only two thickness of material may be permitted to be repaired. The spots must be of at least equal size to those specified and can only be used in well fitting areas and before painting, MIG or MAG welding preferred.

D. Fusion Fillet Welding If allowed, details must be agreed with the component Engineer.

E. Gas Brazing

If allowed the details to be agreed by the Product Engineering Development.

F. Gas-Shielded Metal Arc Brazing

If allowed the details to be agreed by the Product Engineering Development.

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Ford Spot Weld Spec