1. Codes & Standards

2. Codes & Standards Learning Activities View Slides; Lesson Objectives
Read Notes,
Listen to lecture
Do on-line workbook
Lesson Objectives
When you finish this lesson you will understand:
Several of the codes and standards in common use
Keywords
Codes, Standards

3. Industrial Specifications
General Motor/Fisher Body
Specification (MDS-247)
Ford Motor Company
Ford Specification BA13-1
Ford Specification BA13-4
Chrysler Corporation
Specification LP.461K-170
Generally, automotive specifications are used to assess weldability of sheet steels, coated and uncoated. These specifications are largely used for the purpose of qualifying material suppliers and materials for production applications. The automotive qualification tests are mainly concerned with the current level, current range/lobe and electrode life.

4. General Motor/Fisher Body Specification
In this specification (MDS-247), all sheets less than inch thick use the following parameter:
Electrode force: 500 lbs
Tip contact size: inch
Nominal nugget diameter: inch
Minimum nugget diameter: inch
Criteria for rejection of a material include:
Hold time sensitivity (shear-type weld fracture when peel tested)
Brittle welds (during peel tests)
Laminated base metal (observed during peel test)
Narrow lobe (minimum 2000 amps at nominal weld time)
This specification is a procedure to determine weldability lobe. The weldability lobe is a means of graphically expressing the numerous combinations of welding current and weld time that will produce welds which satisfy a specific set of conditions. The left boundary of the lobe defines the combinations of current and time that will produce an acceptable nugget diameter. The right boundary defines the expulsion. Welding at points to the right of this curve results in heavy expulsion, excessive electrode indentation and/or sticking. For convenience, there is a third curve which indicates the curve and time that will produce a nominal diameter weld nugget.

5. Ford Specification BA13-1
Electrode
Configuration
Initial Button Diameter
(inch)
Minimum Button
Diameter (inch)
0.31” x (0.79 cm) (0.71 cm)
0.25” x (0.63 cm) (0.56 cm)
0.19” x (0.48 cm) (0.41 cm)
This specification is a conventional electrode life test which provides data on weld nugget diameter as a function of the number of welds up to 2000 welds. In this test, welds are made at a minimum rate of 20 per minute on galvanized steel panel. Every 250 weld, the weld button diameter is determined using peel test. Failure is determined when the weld nugget is established to be below the minimum specified (for 0.25 inch tip size, the minimum button diameter is 0.22-inch).

6. Ford Specification BA13-4
Actual Thickness
(inch)
Minimum Button
Sizes (inch)
Minimum Current
Range (Ampere)
This specification includes tests for sensitivity to hold time and for current range. To pass the hold time sensitivity test, no shear fracture of the weld is allowed when 30 cycles of hold time are used.
In the current range test, the minimum current (minimum nugget diameter), the maximum (expulsion) current and the current range are determined. Minimum button diameters are given in the above slide for various types of steels and steel thicknesses.

7. Chrysler Corporation Specification LP.461K-170
Heat-Affected Zone
Weld Nugget
This specification includes three parts: the electrode life test (electrode endurance test), a hold time sensitivity test (weld quality test), and the metallographic examination with microhardness measurements.
In this test, a high welding rate of 60 welds per minute is used. Peel tests are performed every 100 welds up to 2000 welds for galvanized steel. The acceptance criteria call for no more than one interface weld fracture or undersize weld.
The hold time sensitivity test requires welding with 30 cycles of hold time. The welds should meet the minimum button size and with no interface-type fracture.
The metallographic examination in this specification includes characterizations of base metal micro-structure, grain size, weld penetration and diameter measurements. In addition, microhardness traverse through the weld area (the above slide). This metallographic examination is to provide additional information about the material properties.
Micro
Hardness
Traverse
Cross Section Through Center of Spot Weld

8. Codes and Equations Used for Electrode Face Selection
Ayers & Fisher
D = 1.5t (Leng)
D = 2t (AWS)
Ford BA 13-4