Improved Impact Properties Research Articles

Intercritical annealing as a means of improving impact properties of plate steel

The influence of long time intercritical heat-treatments (720 to 750 °C) on the impact and tensile properties of ferrite/pearlite steels has been examined. Intercritical annealing enables Mn to diffuse to the α/ γ boundaries and refine the grain-boundary carbides on cooling to room temperature. When the resulting microstructure formed on cooling to room temperature is ferrite/pearlite, this treatment can result in a significant improvement in impact behavior compared to a normalizing treatment. On heating to the intercritical annealing temperature, Mn enrichment of the γ combined with a fast enough cooling rate results in martensite formation. This may be beneficial to both strength and impact behavior at low volume fractions of martensite, but a marked deterioration in impact behavior occurs at high volume fractions, even though grain-boundary carbides remain fine.

Applications Of TEM and image analysis in impact-modified thermoplastics

Polymers can be blended to produce improved properties appropriate for a wide range of applications. For example, rubbers when added to rigid thermoplastic polymers produce blends with improved impact properties. Generally, the properties of blends are dictated by phase morphology, which can be controlled by processing conditions and chemical composition.This study demonstrates that TEM/image analysis can be used to study deformation of dispersed rubber particles in a matrix and to quantify phase morphologies for process optimization. For TEM, ultrathin specimens were produced by microtomy and stained with heavy atoms to enhance contrast between the different phases. In the present examples, thin film samples were embedded in epoxy and sectioned on a LKB Ultramicrotome. For bulk samples, cryogenic thin sectioning was performed using a Reichert Cryo Ultramicrotome. The thin cross-sections were then vapor stained with OsO4. and carbon coated. Electron microscopy was performed on a JEOL 100CX TEM.

Application of 20 MnMoNi 5 5 steel with lowered Si content to heavy thick steam generator tube sheet forgings

The 20 MnMoNi 5 5 steel with a lowered Si content, in which the addition of Al for grain refining is made before vacuum degassing in the steel making process, was applied to the heavy thick tube sheet forging for the steam generator of a light water reactor. The properties of the forging were compared with a forging of the conventional Si/Al deoxidized steel. The steel with lowered Si content showed less A- and V-segregations than the Si/Al deoxidized steel. And also the steel with lowered Si content has improved impact properties and ductility as well as a greater isotropy of properties. The excelent weldability was confirmed by the tangential sectioning test. The less segregated 20 MnMoNi 5 5 steel with lowered Si content, which has improved material properties such as impact properties and weldability, assures a better integrity of the component and easier fabrication.

Morphology of solution-cast films of polypropylene homopolymer/ethylene-propylene random copolymer blends and polypropylene/ethylene-propylene sequential copolymer

Abstract The addition of ethylene-propylene random copolymer (EPR) to polypropylene (PP) homopolymer and the synthesis of polypropylene/ethylene-propylene block-sequential copolymer (PP/E-P) have been developed in order to improve upon the mechanical properties of PP resin. The block-sequential polypropylene/ ethylene-propylene copolymer or the appropriate blend of EPR with PP gives improved impact properties without loss of elastic modulus [1–3].

Rubber‐modified epoxies. II. Morphology and mechanical properties

AbstractA wide range in morphology paralleling a spectrum of phase separated and dissolved rubber, can be developed in rubber‐modified epoxies through control of rubber‐epoxy compatibility and cure conditions. These morphologies result in different stress response mechanisms. Dissolved rubber promotes plastic deformation and necking at low strain rates that provide large increases in the elongation to break. Dissolved rubber is ineffective in providing improvement at impact rates. Phase separated rubber domains can also increase the elongation to break since cavitation is promoted at the interfacial boundary. The elongation is limited to the extent of cavitation and therefore large increases in the energy to break are not found. The presence of rubber domains was found to be a necessary but not sufficient condition for impact energy improvement. Optimum materials contained a relatively large amount of dissolved rubber and a low volume fraction of phase separated rubber. These combine high elongations at low strain rates with improved impact properties.

Influence of carbide thickness on impact transition temperature of ferritic steels

A large number of ferrite–pearlite steels have been examined and measurements made of grain size, pearlite volume fraction, degree of precipitation hardening, and thickness of grain-boundary carbides, the latter being measured using a scanning electron microscope. Multilinear-regression analyses were carried out on these measurements and on the composition of the steels, to obtain statistically the best structure–property relationships for 500;0 FATT, and 54J and 27J Charpy impact transition temperatures. Regression equations based solely on the structural parameters, grain size, precipitation hardening, and carbide thickness were found to give improved predictions over previous regression equations in which no factor for carbide thickness has been included. The importance of carbide thickness in influencing the impact properties was substantiated using data from pearlite-free steels in which the major variable was the carbide thickness. The carbide thickness was found to be dependent primarily on the manganese content and cooling rate from the austenite temperature range, an increase in either leading to finer carbides and improved impact properties. At the lower manganese levels (<1%Mn), micro-alloying additions also were found to influence the carbide thickness.

Factors affecting stress cracking in cold/warm cropping of steel billets

In the forging industry, the traditional method of billet production by sawing is being replaced increasingly by shearing or cropping, as the latter offers substantial economic advantages. A considerable range of steels can be cropped satisfactorily in the cold condition for use by the forging industry. However, a number of steels of specific composition, which are used currently for hot-forged automobile components, cannot be cropped satisfactorily by the conventional cold-cropping method. This is because the billets cropped from these materials tend to exhibit stress cracks on the cropped faces, making them unsuitable for forging. This type of billet defect appears to be the most difficult to prevent, particularly as the cracks may not be visible immediately after shearing and can remain undetected for several hours/days. These delayed cracks and other billet deffects are influenced by several factors, which fall into two main groups. The first of these is metallurgical and primarily relates to the chemical compositions, existing impurities and the physical properties of the bar stocks in as-received condition. The second group consists of mechanical effects such as billet geometry, type of cropping machine and the characteristics of the tooling employed. Both groups of factors are interrelated and the proper selection of the latter is, often, guided by the former. One of the ways of producing crack-free billets is to preheat the bar stock before the cropping operation, which acts primarily to provide an increase of the material ductility and/or improved impact properties. However, it appears that current preheating practice varies widely within the forging industry without any apparent scientific basis. The present paper examines the relevant factors in order to establish their respective influence on stress cracking. Their identification is necessary if guide lines are to be established for either the efficient use of the thermal energy consumed in preheating, or possibly its total elimination through better cropping techniques and improvements in the as-recieved bar stocks.

Carbon fibre and glass fibre hybrid reinforced plastics

A review of the literature on carbon fibre and glass fibre hybrid reinforced plastics is presented. There are indications that the incorporation of both fibres into a single matrix sometimes leads to better properties than would be expected from consideration of the rule of mixtures. The incorporation of glass fibres in cfrp appears to improve impact properties and to increase the strain to failure of the carbon fibre in tension. The addition of carbon fibres to the surface of grp beams markedly increases the flexural modulus. A system of nomenclature for the diverse types of hybrid composite lay up is proposed.

Control-rolled high-strength low-alloy plate steel

In a combined laboratory-mill development program Bethlehem has found that lower carbon and the proper rolling practice provide a desired balance of yield strength and improved impact properties.

High temperature polymers. II. High temperature polymers from 4,4′‐[sulfonylbis‐(p‐phenyleneoxy)]dianiline

AbstractNovel aromatic diamines have been prepared which contain an ordered sequence distribution of thermally stable, flexible, or rigid units. The synthesis of these materials involves a nucleophilic displacement reaction in aprotic solvent with, for example, the alkali metal salt of p‐aminophenol, optionally, the salt of a bisphenol and an activated aromatic halide. Such monomers are useful “building blocks” for various polymeric systems but are of special interest in those which can benefit from the high glass transition temperature imparted by polar or rigid moieties, together with improved impact properties conveyed by either groups. Polyimides and polyamide‐imides are examples and display high heat distortion temperatures, good solvent resistance, excellent mechanical properties, high thermal and oxidative stability and depending on diamine structure and molecular weight, thermoplastic characteristics. The synthesis and properties of polyamides, polyimides and polyamide‐imides based on 4,4′‐[sulfonylbis(p‐phenyleneoxy)] dianiline are presented in this paper.

Improvements in or relating to the reinforcement of plastics sheets or pipes: improved impact properties : Tansley, A. V. UK Patent Specification, 1,197,562 (8 July 1970)

Improvements in or relating to the reinforcement of plastics sheets or pipes: improved impact properties : Tansley, A. V. UK Patent Specification, 1,197,562 (8 July 1970)