On the Relation Between Pressing Energy and Green Strength at Compaction of Hard Metal Powders

AbstractThe relation between pressing energy and green strength is examined experimentally and numerically using a commercially available design of experiment (DOE) software, at compaction of five hard metal powder materials. This is of substantial practical importance, in particular at pressing of complicated geometries when high values on the green strength is necessary. The compaction energy is here experimentally determined at uniaxial compaction of a cylindrical die, filled with powder material, by measuring punch force and compression. The corresponding measurements of the resulting green strength are performed using standard three-point bend (3PB) testing. The statistical analysis of the results shows that the relation between the two properties, pressing energy and green strength, is very close to a linear fit with the coefficient of determination R2 taking on the value 0.92. This suggests that the pressing energy is an important quantity for reaching a target value on the green strength and the linear relation is certainly convenient in particular when compaction of similar materials is at issue. In parallel with the experimental work finite element calculations are performed in order to evaluate the effect from friction between the powder and the die wall, and it was found that this feature has a limited effect on the pressing energy when similar materials are at issue and is not detrimental for the usefulness of the present correlation approach.

Download Full-text

Correlation Between Granule Strength and Green Strength at Compaction of Cemented Carbide Powder Materials

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-06089-1 ◽

2021 ◽

Author(s):

Kristin Salmi ◽

Erik Könberg ◽

Hjalmar Staf ◽

Per-Lennart Larsson

Keyword(s):

Practical Importance ◽

Hard Metal ◽

Strength Properties ◽

Coefficient Of Determination ◽

Carbide Powder ◽

Powder Materials ◽

Metal Powders ◽

Green Strength ◽

Granule Strength ◽

Point Bend

AbstractThe correlation between granule strength and green strength of hard metal powders is examined. The approach is based on experiments and numerics. In the latter case, a Design of Experiment software is used. The granule strength of the powder (particle) is determined by GFP-measurements (“Granularfestigkeits-Prüfsystem”). During this test, a single particle is pressed from one side until breakage. The corresponding measurements of the green strength are done using three-point bend (3PB) testing. The experimental results show that the pressing agent has a strong influence on the behavior of both quantities. The statistical evaluation shows that the relation between the two strength properties is very close to linear with coefficient of determination R2 taking on the value 0.97. This of course indicates that it is possible to get information about one of the properties for a similar set of materials by experimentally determining the other one. This is of substantial practical importance as for one thing it can limit the amount of testing required. Even though the present investigation is pertinent to hard metal powders, the results could be of value for many other types of powder materials.

Download Full-text

Investigation of pre-sprayed powders for electric contact welding

Tekhnicheskiy servis mashin ◽

10.22314/2618-8287-2020-58-1-143-149 ◽

2020 ◽

pp. 143-149

Author(s):

Dinar R. Masalimov ◽

Roman R. Galiullin ◽

Rinat N. Sayfullin ◽

Azamat F. Fayurshin ◽

Linar F. Islamov

Keyword(s):

Adhesion Strength ◽

Electrical Contact ◽

Research Purpose ◽

Flame Spraying ◽

Powder Materials ◽

Electric Contact ◽

Metal Powders ◽

Unstable Flow ◽

Gas Flame ◽

Contact Welding

There are a number of difficulties in the electrical contact welding of powder materials: shedding of powder from the surface of a cylindrical part, impossibility of hardening the layer during welding due to flushing of the powders with coolant and unstable flow of powder into the welding zone. One solution is pre-spraying the powder in some way. (Research purpose). The research purpose is investigating the possibility of electric contact welding of metal powders preliminarily sprayed by a gas-flame method, namely, adhesion strength and losses during preliminary gas-flame spraying of powders. (Materials and methods) Powders of grades PG-NA-01, PrKhIIG4SR, PRZh3.200.28 were sprayed onto flat samples of St3 steel, polished to a roughness of Ra 1.25. The strength of powder adhesion to the base was studied by the cut method. (Results and discussion) The percentage loss of the powder as a whole is 3-23 percent for all the distances studied. The greatest powder losses appear at a distance of more than 180 millimeter from the tip of the burner for powders of grades PG-NA-01 and PrKhIIG4SR. The smallest powder losses were observed for PrZh3.200.28 powder, which totaled 3-7 percent. The maximum adhesion strength of the sprayed powders to the surface was 22.1 megapascals' when spraying the PG-NA-01 powder. The adhesion strength of powders of the grades PrKhIIG4SR and PrZh3.200.28 is small and amounts to 0.2-3 megapascals'. (Conclusions) The use of preliminary flame spraying of powders for their further electric contact welding is possible using PG-NA-01 grade powder, while the best adhesion to the base (that is more than 20 megapascals') is achieved with a spraying distance of 120-140 millimeter. The smallest powder losses during flame spraying are achieved at a spraying distance of 100-160 centimeters', at which the powder loss for the studied grades was 4-12 percent.

Download Full-text

Test Method for Green Strength of Specimens Compacted from Metal Powders

10.1520/b0312 ◽

2008 ◽

Author(s):

Keyword(s):

Test Method ◽

Metal Powders ◽

Green Strength

Download Full-text

Analysis of Densification Process and Structure of PM Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn Alloys

Archives of Metallurgy and Materials ◽

10.2478/amm-2014-0003 ◽

2014 ◽

Vol 59 (1) ◽

pp. 17-23 ◽

Cited By ~ 1

Author(s):

R. Bidulský ◽

J. Bidulská ◽

M. Actis Grande

Keyword(s):

Test Specimen ◽

Hardened Steel ◽

Pressing Pressure ◽

Metal Powders ◽

Compaction Process ◽

Cylinder Test ◽

Die Compaction ◽

Uniaxial Compaction ◽

Compaction Behaviour

Abstract The paper is focused on the role of the pressing pressure on the densification behaviour of PM aluminium alloys. Commercially aluminium based powders Al-Mg-Si-Cu-Fe and Al-Zn-Mg-Cu-Sn were used as materials to be investigated. The apparent density of the powder mixes was determined according to MPIF St. 04. A set of cylinder test specimen 55x10x10 mm3 was uniaxially pressed in a floating hardened steel die. Compaction pressures ranged from 50 MPa up to 700 MPa. Considering the densification of metal powders in uniaxial compaction, quantification of aluminium compaction behaviour was performed. The compressibility behaviour was evaluated, considering the effect on specimens, as well as on their microstructure. The development of compressibility values with pressing pressure enables to characterize the effect of particles geometry and matrix plasticity on the compaction process.

Download Full-text

Numerical Analysis of Metal Powders in Uniaxial Compaction

Materials Science Forum ◽

10.4028/www.scientific.net/msf.591-593.218 ◽

2008 ◽

Vol 591-593 ◽

pp. 218-222

Author(s):

Magna Monteiro Schaerer ◽

Deane Roehl ◽

José Luís Silveira

Keyword(s):

Mechanical Properties ◽

Numerical Analysis ◽

Yield Function ◽

Densification Behavior ◽

Metal Powders ◽

Elastoplastic Model ◽

High Quality ◽

Powder Consolidation ◽

Function Coefficient ◽

Uniaxial Compaction

Powder consolidation constitutes an important step in the manufacture of products of high quality and precision. To obtain these components, with desired forms and final mechanical properties, it is of extreme importance to have knowledge about the processes to obtain powders, compacting and sintering. The objective of this work is to verify which model, obtained from the literature, better describes the compaction densification behavior of iron powder in closed-die. Doraivelu’s criterion was carried through the method of the finite elements with the implementation of an elastoplastic model with hardening. The influence of the yield function coefficient against the relative density was evaluated, as well as, the yield function in the hydrostatic space.

Download Full-text

Statistical Analysis of Results Obtained in the Hardening Surface of the Metal Powder Materials with Optical Radiation Impulses

Scientific Bulletin ◽

10.1515/bsaft-2015-0012 ◽

2015 ◽

Vol 20 (2) ◽

pp. 79-85

Author(s):

Ioan Virca

Keyword(s):

Statistical Analysis ◽

Metal Powder ◽

Voltage Pulse ◽

Optical Radiation ◽

Experimental Program ◽

Energy Sources ◽

Powder Materials ◽

Metal Powders ◽

Analysis Of Results

Abstract The paper presents how is processed the data resulted from application of pulsed optical superficial treatments on surfaces of materials made of metal powders. The parameters of the electrotechnological regime work are variable in the experimental program, namely the distance between the axis focal energy sources and surfaces play, the number of energy pulses applied to the voltage pulse of optical radiation, which causes a statistical analysis more complex, after which it will precise drawing lessons that will lead to a calculation microhardness model in the superificial layer of material.

Download Full-text

Powder materials and methods for their preparation

Tekhnicheskiy servis mashin ◽

10.22314/2618-8287-2020-58-3-108-118 ◽

2020 ◽

pp. 108-118

Author(s):

Anna P. Karpunicheva ◽

Dar’ya A. Lebedeva

Keyword(s):

Powder Metallurgy ◽

Fire Hazard ◽

Point Of View ◽

Research Purpose ◽

Powder Materials ◽

Metal Powders ◽

Resource Saving ◽

Technical Literature ◽

Mechanical Methods ◽

Information Materials

Powder metallurgy, along with other knowledge-intensive industries, is one of the priority areas of high-quality, modern, technologically advanced production, one of the main tasks of which is resource-saving technologies. (Research purpose) The research purpose is in analyzing the existing methods for obtaining metal powders and metal-like compounds in order to review and systematize information. (Materials and methods) The methodological basis is the scientific and technical literature on the topic of manufacturing materials for powder metallurgy. The solution of the problem was carried out by means of comparative and logical analysis based on theoretical and empirical methods of scientific research. (Results and discussion) There are two groups of methods for producing metal powders: mechanical and physical-chemical, as well as methods for manufacturing metal-like compounds. Each of the production methods is analyzed from the point of view of technology, equipment, feasibility of application and the resulting materials. (Conclusions) When manufacturing powders by mechanical methods, there is a high probability of particles of grinding bodies or linings entering the final product. Dispersion allows to automate the process, adjust the properties of powders at a fairly low energy consumption. Physical and chemical methods of production require complex equipment, as well as compliance with safety regulations due to high fire hazard.

Download Full-text