Page 43 - MetalForming February 2019

SOFTWARE,
SENSORS AND
CONTROLS
June 24-25, 2019 Cleveland, OH
MetalForming magazine and
the Precision Metalforming Association (PMA) offer providers of ERP/MRP software, sensors and controls an exclusive opportunity to discuss the Internet of Things (IoT) and plant-floor connectivity with engineers, managers and other team members representing metal-stamping and fabricating companies.
Conference activities include:
• Technology demonstrations by
leading suppliers;
• Presentations describing
successful IoT projects at metalforming and fabricating facilities; and
• Keynote presentations on IoT technology developments and implementation trends.
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The Science of Forming
Table—Differences in Tensile Bars
Tensile bar
Width (mm)
Original gauge length (mm)
ASTM
12.5
50
DIN
20
80
JIS
25
50
0.5 in.
2.0 in.
ASTM Speciemen
25 mm
50 mm
JIS #5 Speciemen
20 mm
80 mm
DIN 20X80 Speciemen
Fig. 2—Tensile bars, depending on the par- ticular testing standard organization, fea- ture differing widths and gauge lengths.
load divided by the cross-sectional area. Even though each of the bars feature a different sample width (and, there- fore, a different cross-section), the load is normalized by this value, which negates differences from sample shape.
Why This Matters
There was a time when all test results received from your service cen- ter likely came from ASTM tests. In the 1990s, New Domestic automakers, pri- marily from Japan and Germany, ramped up production within the United States. For a host of reasons, they sourced sig- nificant tonnage with U.S.-based steel- makers rather than importing sheet- metal from their home countries.
The requirements for steel grades needed by the New Domestics do not differ significantly than those from the Big Three automakers. What is different: how the sheetmetal should be tested —both the shape of the ASTM/JIS/DIN tensile bar and orientation relative to rolling direction.
Sheetmetal pro- duction includes the same con- straints as many manufacturing environments, with batch production of the same product as
the ideal scenario. A heat of steel may total 300 tons of the same composition, and most steel producers target three heats—roughly 1000 tons—as a mini- mum production sequence for one composition.
Consider this scenario: If the end customer needs only 800 tons, that leaves several coils that might be sold to service centers. If the primary cus- tomer needs JIS bars, then all coils from that sequence will be tested with JIS bars. Any coils making it to service centers likely include a JIS-based cer- tified-metal-property document.
Suppose the certs report 32-percent elongation for a coil, which satisfies the requirement of a minimum 30-per- cent elongation. A JIS tensile bar will generate a value a few percentage points higher than that generated from an ASTM tensile bar. Combine this with the normal test-to-test variability, and stamping performance may not coin- cide with your expectations.
Some service centers will provide a copy of the certification document directly from the producing mill. This should indicate the tensile-bar type as well as the test direction listed as L or T, referring to longitudinal or transverse relative to the rolling direction. Other service centers will reprint the test results on their own stationery, but may leave off information about the chosen test bar and test direction. Still others will run their own test, but may or may not include bar type and sample orientation.
When purchasing sheetmetal, check the certified-metal-property document to make sure it has been tested appro- priately to your chosen standards. If not, ask your service center to test a sample to your standard-of-choice at an accredited lab. It may save you from an unwanted surprise. MF
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