Janka Majerníková

The Comparison of Properties of Tinplates during Uniaxial and Biaxial Stress

--------------------------------------------------------ABSTRACT------------------------------------------------------------The majority of thin steel sheets is used to make of food covers, cans, capsules and other products, which are produced by metal forming. Concerning considerable changes in production of tinplates and still higher requests on their properties there is requirement to use such methods on their evaluation, which are able to determine especially mechanical and plastic properties of sheets quickly and with the low costs. Following of present know-how there were developed new testing methods, which correspond more to steel sheets stress during technological treatment (concerning their stress-strain state). In the contribution we deal with the comparison of properties of tinplates during uniaxial tensile test and biaxial tensile test.

Punch-Die Gap Effect on Blanked Edge in Fine Blanking of Low-Carbon, Micro-Alloyed and High-Strength Steels

This paper analyzes the effect of the punch-die gap on blanked edge quality in fine blanking. The objective is to determine basic mechanical properties of galvanized multiphase steel sheets with a thickness of 0.75, 0.80 and 0.85 mm by a single-axis tensile test, determine the effect of the punch-die gap on plastic phase depth [hv] expressed as the relation of hv to a0, and, finally, determine the effect of material properties of blanked sheet metal on blanked edge quality expressed as the relation of hv to a0.

The Loss of Plasticity Stability

The real values of plastic properties of steel sheets are basic input parameters for objectification of deep drawing technological processes. The loss of stability of plastic properties is the criterion of evaluation of plastic properties of steel sheets in most cases. The loss of stability of plastic properties depends on stress-strain scheme in real conditions of deep drawing of sheets. In the contribution will be evaluated the loss of plastic properties stability of thin double reduced packaging sheets made from low carbon steels. For evaluation of strength and plastic properties of thin packaging sheets is the tensile test most used at present. The material is stressed by uniaxial tension during this test. In the conditions of technological processes of drawing, which thin packaging sheets are mostly treating, is this way of stress not very objective. In most cases it deals about multiaxial stress of sheet by deformation of sheet to require draw cup. At the present, the biggest problem of thin steel sheets by uniaxial tension test evaluation is the loss of plastic deformation stability (localization of plastic deformation). Therefore, obtained results of plastic deformation during this test do not correspond with real plastic properties of thin steel sheets. In the contribution, will be compared the evaluation of plastic properties of these sheets by uniaxial and biaxial load. Biaxial load is unfavourable from stress point, but less sensitive on loss stability of plastic deformation from conditions test influence point.

The Loss of Plastic Properties Stability of Thin Tinplates and its Influence on Change of Corrosive Resistance

Nowadays the thin tinplates are the most important material for a wraps production.Predominant majority of these sheets are treated by drawing, by which are made both parts of tin sheets. By reduction of thicknesses of thin steel sheets and by require speed of deformation during the wraps production made by drawing often leads to the loss of stability of plastic deformation and to its localization. This localization of deformation considerably influences the change of thickness of protective tin layer and its integrity. Because of this it leads to the reduction of thin steel sheets resistance towards corrosion.In contribution are therefore dependencies of stress and strain by uniaxial and biaxial tensile test by different levels of deformation of two types of sheets monitored. After plastic deformation were sheets put under the impact of corrosion environment and was evaluating influence of deformation largeness and localization of deformation at the corrosive resistance of thin tinplates sheets. In contribution are also analyzed some of the cases of concrete corrosive damage of lids, so-called twist lids.

Clinching of Dual-Phase Steels as an Alternative to Resistance Spot Welding

Resistance spot welding is the dominant method for joining the materials in the car body production. Progressive materials are being developed to improve the car’s fuel consumption and the safety of passengers as well. Advanced high strength dual-phase steels are such materials. Despite of the dominancy of resistance spot welding in car body production, innovative methods are being developed to reduce the joining time, process costs and improve the load-bearing capacity of a particular joint. Mechanical clinching is such process. The research focused on the evaluation of the possibility of clinching as an alternative method to the resistance spot welding. Experimental samples were prepared from dual-phase steel sheets DP600. The samples were tested by uniaxial tensile test, microhardness test and metallographic observations. Both joining methods have advantages and disadvantages which could destine them for specific utilization. Clinching joining is a progressive, fast and low-cost technique, but the joint’s load-bearing capacity is lower when compared to resistance spot weld.

Method of Evaluation of the Properties of Thin Steel Sheets by Springback Test

Production of thin packaging sheets has gone through significant changes in recent years. Thickness of thin packaging sheets has decreased from 0.24mm down to 0.14 – 0.18mm due to the material saving, and the thickness of tin coating layer has decreased as well. Thin packaging sheets with the thickness lower than 0.18mm are produced with so called double reduction. Materials produced with this method possess higher strength properties and lower plastic properties. There exist several tests for examination of strength and plastic properties. Requirements of the processors of these sheets are that these tests are simple, without a complicated production of specimens, and easily repeatable. Exactly because of these reasons, the springback test is used for evaluation of double reduced packaging sheets by many processors from various countries. This contribution compares properties of double reduced thin packaging sheets obtained with the springback test, uniaxial tensile test and biaxial tensile test. Goal of this comparison is to objectify mechanical and plastic properties of packaging sheets obtained with the individual tests.

The Evaluation of Properties of Mechanically Clinched Joints Made of Ferrous and Non-Ferrous Materials

Nowadays, there are several reasons for the utilization of the sheets made of aluminum in the car body production. Besides decreasing the car body weight, there is a need to reduce fuel consumption of the vehicle as well as the environmental impact by lower production of emissions. Moreover, such reasons are mutually dependent or influence each other. The application of the aluminum sheets in hybrid car body production resulted in the need for innovative joining techniques, which could make it possible to successfully join sheets from aluminum alloys. Mechanical clinching is one of the new or innovative joining techniques, which belongs to cold-forming joining process, which makes it possible to join different kinds and thicknesses of sheets. Individual materials and thicknesses can be combined. The mechanically clinched joints are durable, and the joining process duration is very fast (duration of 1s) and does not have a distinctive impact on the environment; a protective layer of the sheets remains intact. The paper focuses on the evaluation of the properties of hybrid joints that were prepared by the single stroke clinching process with a rigid die. The hot-dip galvanized steel sheets DC06 and H220PD combined with the sheets from aluminum alloys EN AW 5754 (having different values of the hardness – H11, H22, and H24) and EN AW 6082 were used for joining. The results from experiments confirmed the mechanical clinching is the suitable technique for joining such combination of sheets. However, some considerations, such as the arrangement of the sheets about the punch and die, must be regarded.

Analysis of Cutting Surface During Cutting of Electric Sheets

The contribution evaluates the influence of the size of the cutting gap on the quality of the cutting surface during the cutting process. Four types of electrical sheets were evaluated. Examined sheet types have the nominal thickness of 0.65 and 0.5 mm. Sheets differ in mechanical properties (yield strength, ultimate tensile strength, and elongation). For the impact analysis, four values of the 0.02, 0.05, 0.1, and 0.2 mm cutting gap were used.

Increasing of Durability of Cutting Tools

The article evaluates durability of punches and cutting tools when cutting of the cut-outs. Durability of punches made of the same material without coating, with the TiCN-MP coating and with the TiN coating is compared. Durability is evaluated by the tolerance of the cut-outs. Border durability, which requires grinding of the tool, is a determined durability, at which the deviation of the tolerance of a cut-out is at the lowest border. By comparing the dependency of change of the holes’ dimensions on the number of strokes in the case of all three types of punches, it can be stated that the durability increased by 10–12 times in the case of the tools with coatings.

Inhomogeneous plastic deformation and fracture of double reduced thin plates

Original scientific paper This paper discusses causes and consequences of plastic deformation of packaging sheets which are nowadays used in a wide range of applications. The article deals with a specific inhomogeneity and localization of plastic deformation which is analysed in detail. For material testing, uniaxial and biaxial tensile test was used and the results were also compared and evaluated. In the last part of this paper microstructure of material was analysed by localized deformations.