The following report and data are courtesy of Ohio State University Graduate Student, Eren Billur, from the Center for Precision Forming (CPF) as it appeared in FMA Publication, The Stamping Journal.

Die materials and wear in stamping AHSS, Part III

Research results and recommended die materials and lubrications

Many cast-iron and steel grades are used for manufacturing dies in the stamping industry. The cost of these materials varies considerably, but with appropriate surface treatments, coatings, and lubricants, a cost-effective die material can outperform the expensive ones.

Die material selection requires a systematic evaluation of tool materials, coatings, and heat treatments, with cost considered as a parameter. Having a proper knowledge of surface treatments and coatings can save money in stamping die manufacturing.

Comparative Studies

Several studies rank tool materials and coatings using a widely accepted standard test.^{1, 2} However, they do not give quantitative information regarding tool life under practical stamping conditions. There are a number of publications on comparative die wear studies, yet not many of them use advanced high-strength steel (AHSS) as sheet material. Figure 1 provides a summary of ranking results.³

Benchmark Studies

Benchmark studies give a numeric comparison of tool life (number of good parts stamped) for a given tool material and coating. Forming tests were conducted until galling and scratches were visible on the sheet metal.

The first study was a channel forming test using uncoated DP600. Figure 2 shows the results of this study.

A similar study was performed with uncoated DP980 material using the part seen in Figure 3. The forming tests were conducted up to52,000 stampings, and results are shown in the figure.4  As a benchmark, forming of a B-pillar inner also showed that conventional tool materials fail from heavy galling after making a few hundred stampings in AHSS. Figure 4 shows how the tool life of D2 changes with three different coatings.5

Guidelines and Recommendations

For the forming of AHSS with 500-to 800-MPa tensile strength, several tool steel companies, industrial experts, and research facilities recommend the following tool materials, treatments, and coatings.^6,7

• Hardened Carmo
• D2 + TD
• D2 + PVD CrN
• D2 + CVD TiC
• Vanadis 4E + PVD CrN
• Vanadis 4E + CVD TiC
• Vanadis 6 + PVD CrN
• Vanadis 6 + CVD TiC
• Hardened Vancron 40

FEA Prediction of Die Wear

The wear coefficient can be used to simulate wear progression using the pressure distribution and sliding distances are not constant throughout a stamping die, inserts may be used to reduce wear at critical locations in the dies. At this point, simulations can be useful for the proper design of die inserts. Figure 5 shows how simulations can be used to determine the locations of mild and severe die wear.

When the wear coefficient and surface hardness of tools and sheet used to estimate how many successful parts can be stamped before galling and scratches become visible. With these parameters, we can estimate tool life, and insert design can be improved.

The original version of this article from the May 2010 version of The Stamping Journal is available at http://nsmwww.eng.ohio-state.edu/May10R_DUpdate_628-9.pdf 

Slightly more Americans now say the United States makes better-quality vehicles than Asia does, with 38 percent saying U.S. cars are best and 33 percent naming autos made by Asian countries, according to an Associated Press-GfK Poll.

The survey suggests those numbers are largely fueled by a plunge in Toyota's reputation and an upsurge in Ford's. The poll was conducted in March, as Toyota was being roiled by nightmarish publicity over its recall of more than 8 million vehicles around the globe and allegations that it responded sluggishly to safety concerns.

Though the U.S. advantage is modest, it marks a significant turnabout for American automakers battered by recession and relentless competition from foreign manufacturers. When the same question was asked in a December 2006 AP-AOL poll, 46 percent said Asian countries made superior cars, while just 29 percent preferred American vehicles, reflecting a perception of U.S. automotive inferiority that began taking hold about three decades ago.

"Toyota's problems are not to be minimized here," David Williams, dean of the business administration school at Wayne State University in Detroit, Mich., said in explaining the attitude shift.

In both AP polls, Japan – home to brands like Toyota, Honda and Nissan – was by far the dominant Asian nation volunteered as producing the best cars. European autos – which include BMW, Mercedes Benz and Volkswagen – were called top quality by 15 percent last month, about the same as the 17 percent who said so four years ago.

Williams and others also cited a fresh look Americans are giving U.S. automakers, especially Ford and General Motors. Though GM and Chrysler went through bankruptcy last year and the federal government invested $80 billion to keep them afloat, GM has revamped its lineup with more fuel-efficient and crossover vehicles. Analysts say Ford revived its reputation by not accepting the taxpayer bailout and improving its vehicles' gasoline mileage.

The most notable findings of the poll were:

•Fifty-six percent own vehicles made by U.S. automakers, about the same as in 2006.

•Eight in 10 live in households with autos, including about two-thirds who have two or more cars.

•Six in 10 autos were bought used.

•About four in 10 say their dream car would be a foreign brand, compared with three in 10 wishing for a domestic car.

View the entire, "AP-GfK Poll: U.S. Cars Superior To Asian Cars" article by AP writer Alan Fram.

According to the Detroit Free Press, "The move doesn't affect city or county property tax collections but makes Ford eligible for up to $10 million in state business. The company said it plans to invest up to $100 million in the plant to make parts for electric vehicles."

The driving market of this demand? It's apparently Mexico.

Closely related to the North American auto parts industry, the Mexican auto parts industry has approximately 1,000 auto parts manufacturers. Approximately 70% of these operations are subsidiaries of foreign corporations, including those from the United States and Canada. The export-oriented auto industry is Mexico’s largest single manufacturing sector. As a result of Mexico’s low labor costs and current technological developments in the auto industry, many automotive companies are investing in Mexico. Companies look to Mexico for lower manufacturing and export costs.

According to the Mexican Auto Association, the best export opportunities for North American firms are OEM parts and components, hybrid vehicle components, suspension systems, along with materials, pre-assembly components such as small and progressive stampings, electronic components, equipment and specialized tooling.

It is predicted that U.S. and Canadian automotive parts, component and equipment manufacturers will realize an increase in export sales as global assembly plants relocated to Mexico.