Low+Stress+Die+Stamp+White+Paper+Atema+Inc+Feb+2012

Date Feb 2012 Atema Inc. All rights reserved

742 N. LaSalle St. Chicago, IL 60654

312.861.3000 www.atema.com

Guide To The Definition and Understanding

Of Low Stress Die Stamp In the Structural Steel Industry

By Terry E. Logan Vice President

CQE, CQA, CMfgE, CWI, RAB, SSMBB

An Atema Inc. White Paper

Date Feb 2012 Page 2 of 9 Atema Inc. All rights reserved

Contents Introduction.3 Problem statement3 Definitions4Identification...5 Die Stamping Practice..5 Need for Low Stress Die Stamping...6 Die Stamp Sized Defined..6 Recommendations.7 Summary..8 References...9 Relevant Researched Documents.9


Introduction Within the Structural Steel industry, the phrase low stress die stamp has been used to identify how steel is to be identified (marked) by means other than paint, chalk, etc. The intent of this White Paper is to provide a single source for definition, and reference on what exactly a low stress die stamp consists of.

Problem Statement There are numerous references to the phrase low stress die stamp in codes, contract requirement, state specifications and even federal guidelines, yet very few of these documents define or explain the tool criteria. Research into AWS, AREMA or AASHTO documents gives no guidance, which in turn creates confusion during quality inspections, or purchase orders to suppliers who are required to adhere to the requirement. Thus the user is left in limbo on what the exact criteria is. This paper will give guidance to the reader in the definition of low stress die stamps.


Definitions Identification Marking Identification marking consists of letters, numbers, directional arrows or symbols intentionally added to metal surfaces of components or components parts for identification or instructional purposes. Marking can be separated into two categories: permanent and temporary. Permanent Marking Permanent marking is marking which is intended to remain integral with a component or component part for purposes of permanent identification. Temporary Marking Temporary marking is marking which is intended to remain integral with a component or component part for a limited time only. Temporary marking may be applied for identification, recording inspection information or dimensional layout or control. Low Stress Die Stamp A low stress die stamp is defined as a round bottom impression tool producing an indentation conforming to tabulated dimensions.


Identification The structural industry has always required surface marking on components or component parts for purposes of identification in steel making, fabrication, erection, dimensional layout, quality classification or other needs to complete projects. Requirements for marking of raw materials have also been vital in the industry as it serves to show critical information in which traceability is established. Temporary marking is generally used for short term identification and is not permanently applied. Permanent markings are used to allow for identification during any time of the life cycle of the item. This allows for traceability and item part number recognition at any time. Die Stamping Practice Die stamping normally consists of a single letter or number stamp, or in automated machinery, a single V point style punch in consecutive punches to create a letter or number. Both are applied by force to leave an indentation into the steel. The basic intent is a round bottom impression tool producing an indentation to make a permanent marking into the steel for identification purposes. The imprint in the steel should be as light as is practical and still allow for easy reading.


Need for Low Stress Die Stamping Die stamp impressions can cause stress concentrations which may lead to fatigue cracking; this is a crucial negative situation, especially for the structural steel bridge industry. AWS has long stated that only low stress stamps should be used in areas of bridge members subject to tensile stress, as other die stamps may cause the same fatigue cracking problem. Die Stamp Sizes Defined As noted before, die stamps consist of a single letter, number, or a single V point style punch in consecutive punches to create a letter or number. A low stress die stamp needs to have a round bottom to produce an indentation which will not create fatigue cracking. The below table shows the radius of the die stamp tip for the appropriate character size.

Character Size Minimum tip radius

Nominal impression width for 0.010 inch depth

1/16 inch 0.005 inch 0.020 inch 3/32 .006 .021 1/8 .007 .022 3/16 .008 .026 1/4 .010 .031 3/8 .014 .042 1/2 .020 .062


Recommendations Ordering Low Stress Dies In order to assure the proper application of low stress die stamp impressions, the process must begin at the die stamp purchase order step. The following recommendations are made when purchasing dies;

The company purchasing agent should include the above table within the die stamp purchase order.

The purchase order should also include a request

for Certificate of Compliance (CoC) stating the radius at the end of the die stamps are at the minimum as noted for each size character.

Maintain the CoC on file for reference. Verification of Low Stress Dies There are several ways to verify the radius of a low stress die stamp beyond the CoC provided by the stamp supplier. These include

Measuring the radius with an optical comparator. Use of a radius gage.

Use a die stamp on wood or steel and make an

impression. Then make a mold with clay, drywall mud, etc. and measure the radius of the mold with one of the above methods.

[Note: Another white paper on the measurement instruction of these techniques will be published.]


Summary The intent of this White Paper was to provide a single source for definition, reference and sizes for low stress die stamps. As the structural steel industry advances to align with other industries in advanced practices, the need for clarification and classification of tooling (or methods) needs to be published in order to eliminate confusion and lack of consistency. Hence the reasoning for this publication. As will all projects or contracts, every party must agree on the conditions and criteria for product, process and application methods. Use of this white paper can assist in making such specifications clearer. The dimensional sizes referenced within this paper were the results of research within the references noted herein. There is never a time, paper or method which can assure the radius sizes mentioned will fully prevent detrimental situations. Yet the application and history of the references, and practices within industry have proven a high degree of certainty in the use of these recommended low stress die stamp sizes.


References MIL-STD-792F (SH) 19 May 2006 AASHTO/AWS D1.5M/D1.5:2010 An American National Standard Bridge Welding Code RDT Standard F 7-3T Marking of Components and Parts June 1975 U.S. Energy Research and Development Administration Division of Reactor Research and Development Relevant Researched Documents Federal Highway DOT Spec 506 AREMA Letter Ballot No. 15-10-18 AISC Code of Standard Practice for Buildings and Bridges ASTM A6/6M

ContentsIntroductionProblem StatementDefinitions

Low+Stress+Die+Stamp+White+Paper+Atema+Inc+Feb+2012

Documents

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