ASTM D3433 Fracture Strength in Cleavage of Adhesives in Bonded Metal Joints

The ASTM D3433 test method includes the determination of adhesive cleavage fracture strength when evaluated on standard specimens and under specified preparation and testing conditions. This test method is important for developing design parameters for bonded assemblies.

TRUSTED BY ENGINEERS FROM

Introduction

ASTM E340 Macroetching is used to reveal the heterogeneity of metals and alloys. Metallographic specimens and chemical analyses will provide detailed information about specific localities. Still, they can only give data about variation from one place to another if an excessive number of specimens are taken. The information about chemical composition variations is strictly qualitative; however, the locations of extremes in segregation will be displayed. Chemical studies or other methods of establishing the chemical composition would be required to ascertain the degree of variation. Macroetching will also reveal the existence of discontinuities and voids, such as seams, laps, porosity, flakes, bursts, extrusion rupture, cracks, and so on.

Scope of Microteaching in Metals

The ASTM E340 macroetch test is a welding quality assurance test that involves preparing a specimen with a fine finish, etching it, and examining it under low magnification. This test reveals the general microstructure of the weld metal, the heat-affected zone, and any surface defects that may exist. The macroetch test is a significant quality assurance tool in welding. It can reveal possible weld problems, such as metal flaws, heat-affected zones, and surface defects. These issues can be corrected before they cause problems in the finished output. Macroetching can reveal differences in structure, such as grain size, flow lines, columnar structure, and dendrites, as well as chemical composition, including segregation, carbide and ferrite banding, coring, inclusions, and depth of carburization or decarburization.

Procedure

A sample is cut, ground, polished, and then etched with a chemical reagent. Then, the etched surface is inspected visually or using low magnification. Macroetching is mainly used to evaluate the quality of welds and fracture surfaces. Information can be acquired from the sample microstructure. It includes grain size inclusions, segregation, and discontinuities. Following the macro etch test, a report is generated describing the weld metal, heat-affected zone, and any flaws discovered. This report can determine if the weld meets the application quality standards.

Sample Size

The following are the technical specifications of ASTM E340:

Sample dimension	The sample size varies depending on the material, equipment available, and test objectives. The standard doesn’t prescribe exact dimensions, as the sample size is typically chosen to fit the features or defects being investigated.
Sample thickness	Samples should be thick enough to withstand polishing and etching without warping. A section of the material can be cut for large structures or heavy castings.
Sample reagents	The etching solution depends on the material being tested. Common reagents include hydrochloric acid, nitric acid, or a mix with other chemicals based on the metal type.

Result

Macroetching can reveal a variety of information, including:

Structure variations: Grain size, dendrites, and columnar structure
Chemical composition variations: Segregation, coring, and banding
Discontinuities: Laps, seams, cracks, porosity, bursts, pipe, and flakes

Conclusion

The ASTM E340 Macroetching is widely used for quality control in the steel industry to assess the tone of heat in billets regarding inclusions, segregation, and structure. Forge shops also use macro etching to highlight flow lines while determining the optimal forging technique, die design, and metal flow. Forging shops and foundries also use macro etching to detect internal problems and surface imperfections. The copper industry uses macro-etching to regulate surface porosity in wire bars. Macro etching analyzes extrusions and other products like forgings and sheets in aluminum. Defects such as coring, cracks, and porthole die welds are identified.

FAQs

What is the macro etching process?

Inspectors grind and polish the samples, etching the surface of the cross-section with a chemical reagent. This process distinguishes the base metal, heat-affected zone (HAZ), and weld areas for examination while exposing the material's flow lines and microstructure.

What is the chemical used in macro etching?

The most common reagent for macro etching iron and steel is a 1:1 mixture, by volume, of concentrated hydrochloric acid and water. Other reagents included sulphuric acid, ammonium persulfate, and nitric acid.

What is the difference between macro etching and micro etching?

Macro etching enables investigation of the sample surface by eye or magnifying glass (magnification up to 25x). Micro etching enables microscopic inspection at magnifications up to 1,000x (light microscopy) or more (electron microscopy).