Overlay Strip Research Articles

Strip casting using a roll caster equipped with a scraper

An Al-Mg strip without center segregation could be cast using a single-roll caster equipped with a scraper at speed of 40 m/min. The scraper was useful for flattening a free solidified surface and for cooling the solidification layer by pushing the solidification layer to the roll. Clad strips consisting of 1) an Al-Mn base strip and an Al-Mg overlay strip and 2) an Al base strip and an Al-Sn-Cu overlay strip could be cast using an unequal-diameter twin-roll caster equipped with a scraper at speeds of 30 m/min and 15 m/min, respectively. The base strip and overlay strip were strongly bonded at the interface between the base strip and the overlay strip. The elements of the overlay strip did not diffuse into the base strip. The scraper played two roles in the casting of the clad strip: prevention of the mixture of two kinds of molten metal and making the surface of the base strip a semisolid of high solid fraction.

Experimental and numerical study on behaviour of HSFRC overlay strip strengthened flexural deficient RC beams

Reinforcing the concrete matrix using the steel fibres is an efficient technique for improving the mechanical characteristics of the concrete matrix. In the present study, at first, hybrid steel fibre reinforced concrete (HSFRC) consisting of micro- and macro- steel fibres in the fixed ratio of 1:3 in the concrete mixture is developed for repair applications of deficient/damaged reinforced concrete (RC) structures. HSFRC with 1.5% volume fraction of hybrid fibres is used for pre-casting of overlay strips for retrofitting of flexural deficient (FD-30% deficient) beams. Analytical formulations are presented to arrive at thickness and reinforcements of HSFRC overlay strip for the flexural deficient RC beams to reach the required level of load carrying capacity. HSFRC overlay strips are affixed to the bottom surface of flexural deficient RC beams. Experimental studies are carried out on control, flexural deficient and HSFRC overlay strengthened flexural deficient (HSFRC-SFD) RC beams under static and fatigue loading. It is noted that HSFRC overlay strip of 20 mm thickness has improved the ultimate load and fatigue life of flexural deficient RC beam surpassing that of the control beam (without flexural deficiency). Expression relating stress in reinforcement steel and number of fatigue cycles for failure of RC beams is proposed based on experimental data. This study has demonstrated the efficacy of application of HSFRC overlay strip for retrofitting of flexural deficient beams in easier, cost-effective and effective manner.

Effect of Latent Heat of Aluminum Alloys on Bonding between Strips in Clad Strip Cast by a Twin-Roll Caster

This study shows that the latent heat of the aluminum alloy in an overlay strip is the key factor affecting the bonding quality of clad strips fabricated by a vertical-type tandem twin-roll caster. Three-layer clad strips, for which the base strip was 3003 aluminum alloy and the overlay strip was Al-1%Si, Al-2%Si, Al-11%Si (4045), Al-2%Mg, and Al-4.5%Mg (5182), respectively, were cast. The 4045 overlay strip bonded to the base strip. However, overlay strips made of the other alloys did not bond to the base strip. The latent heat of Si is much higher than that of Al, which in turn is higher than that of Mg. Therefore, the latent heat of the 4045 alloy was higher than that of the other alloys. The high latent heat of the 4045 alloy allowed it to heat the base strip to a temperature at which bonding was possible.

Stellite Surfacing Technology

Currently, there are no methods for calculating the operating conditions of automatic submerged overlay welding (surfacing) with a sintered strip that would concider the features and technological parameters affecting the formation of weld metal. The dependences presented in the article indicate that the magnitude of the welding current has the greatest influence on the penetration depth, while the dependence on the voltage and the welding speed is insignificant. Accordingly, as the voltage increases, an increase in penetration occurs, but in the case of a surfacing rate, an inverse relationship is observed. The developed models are 95% adequate.An experiment was performed to determine the influence of the parameters of the overlay strip on the structure and properties of the weld metal.

Effect of Base Strip Temperature on Bonding of Three-Layer Clad Strip Cast by a Vertical-Type Tandem Twin Roll Caster

The effect of the base strip temperature on the bonding between base strip and overlay strips in a three-layer clad strip cast by a vertical-type tandem twin roll caster was investigated. The base strip was 3003 aluminum alloy and the overlay strip was 4045 aluminum alloy. The bonding was investigated for base strip temperatures ranging from 200 °C to 550 °C. The bonding condition was investigated by cold-rolling, bending-to-failure test and tensile shear test. The shear stress increased with the base strip temperature. Sound bonding was achieved at base strip temperatures higher than 450 °C. The results of this study indicated that the second caster is not required to be set below the first roll caster.

Three-Layer Clad Strip Casting Using a Vertical Type Tandem Twin Roll Caster

This paper shows improvements made to a vertical type tandem twin roll caster and the appropriate casting conditions necessary to cast three-layer clad strips, the base strip of which has a lower solidification temperature than the overlay strip. In experiments, 4045 aluminum alloy was used for the base strip and 3003 aluminum alloy was used for the overlay strips. The roll speed was 30 m/min. By connecting the overlay strips to the base strip one at a time and cooling the base strip to between 450 and 530°C after applying the first overlay strip, a sound three-layer clad strip – defined as one in which the interfaces between strips are clear and do not separate during bending-to-failure tests – could be cast. The tensile shear testing between the base and second overlay strip was improved as the base-strip temperature was increased to 450-530°C range.

Casting of aluminum alloy clad strip by an unequal diameter twin-roll caster equipped with a scraper

A single-roll caster equipped with two scrapers and an unequal-diameter twin-roll caster equipped with two scrapers are proposed for casting clad strip without centerline porosity or segregation. Although usually found in roll cast 5182 strip, no centerline porosity or segregation occurred in the 5182 strip, which was the overlay clad strip cast by both types of roll casters. The interface between the 5182 strips and the 3003 base strip was clear. The two strips consisting of layers of the clad strip were bonded strongly at the interface. Both roll casters could cast the clad strip at 30 m/min. This casting speed is much higher than that for the conventional twin-roll caster for aluminum alloys.

Casting of an Mg Alloy Clad Strip Using a Twin Roll Caster Equipped with a Scraper

Casting of an Mg alloy clad strip was attempted with a twin roll caster equipped with a scraper in an oxidizing atmosphere. The base strip was AM60 and the overlay strip was AZ121. The AM60 strip was cast with a roll, and the upper side of the strip was scribed by the scraper. The molten AZ121 was poured on the scribed AM60 strip. The scribed surface of AM60 contacted the molten metal of AZ121 without exposure to the atmosphere. Therefore, the scribed surface was not oxidized. Most of the AZ121 strip was solidified by the other roll. The casting speed was 30 m/min. The roll load was 0.05 kN/mm. The roll speed was very high and the roll load was very small. However, the strips were bonded, and they did not peel with bending until breaking. The interface between the two strips was clear. When AM60 was on the outer side, the results of the V-bending test and the Erichsen test were better. These results mean that the ductility of AZ121 was improved by cladding with AM60.

Investigations on RC Beams Retrofitted with UHSCC Overlay under Fatigue Loading

The present study aims to investigate the use of Ultra High Strength Cementious Composite (UHSCC) overlay strips for strengthening of pre-damaged RC beams. Fatigue loading was conducted in the study, one control beam was tested up to failure. Preloading of 80-90% in terms of number of cycles to failure was applied keeping stress ratio as 0.2 and frequency as 3Hz. Constant amplitude loading spectrum with different maxima minima but keeping stress ratio same was applied to control beam to examine any changes in structural behavior such as deflection and stiffness degradation of beams. The beams used were made of RCC with dimension 1500x100x200mm. The strengthened beams were tested to extract the parameters such as cycles for failure, load, deflection, crack initiation and failure phenomenon. It was observed that the beams retrofitted with UHSCC overlay strips performed efficiently in terms of number cycles to failure in comparison with conventional RCC beams under fatigue loading. Preloaded fatigue beam (FB1) had 17.6% higher load carrying capacity as compared to the control beam. Similarly preloaded fatigue beam (FB2) had 11.7% higher load carrying capacity as compared to the control beam. Acoustic Emission technique is a novel Non-destructive testing method which is used to identify the crack propagation and physical behavior of the beam at selected locations during the onset of loading, which gives a precise idea of the crack initiation and crack propagation under different loading condition.

Casting of Clad Strip by a Vertical Type Twin Roll Caster

A sound three-layer clad strip of 4045, 3003, and 4045 was cast by a vertical type tandem twin roll caster. However, a sound three-layer clad strip of 5182, 3003, and 5182 could not be cast. The 5182 overlay strip did not bond to the 3003 base strip. The latent heat of Si and Mg are 1787 kJ/kg and 230 kJ/kg, respectively. The latent heat affected the rise in temperature of the base strip. The 3003 was not heated up to a temperature suitable for bonding with the 5182 overlay strip. A sound two-layer clad strip of 3003 and 5182 could be cast by a twin roll caster equipped with a scraper. The temperature of the 3003 was near the solidus line, and sound bonding occurred.

A Vertical Type Tandem Twin Roll Caster for Clad Strip Equipped with a Scraper

A vertical type tandem twin roll caster equipped with a scraper for the clad strip was invented. This roll caster could cast three layers clad strip which base strip had lower melting point than that of the overlay strips. The base strip was cast by an upper twin roll caster and the overlay strips were cast by a lower twin roll caster. The scrapers were attached to the lower twin roll caster, and were innovated to cast this type of three layers of clad strip. Solidification layers those became the overlay strips were pulled from between the scraper and the roll. The melt of the alloy which was as same as the base strip was poured between the scraper and the base strip. This melt connect the overlay strip and the base strip. The base strip was not re-melted. The scraper enabled that the solidification layer of the overlay strip contact to the melt of the base strip without mixing of the melt of the base and overlay strip. In this way, the sound three layers clad strip which base strip had lower melting point than that of the overlay strip could be cast by the vertical type tandem twin roll caster equipped with a scraper.

A Roll Caster to Cast Clad Strip

A tandem-type roll caster that can cast a three-layered clad strip was developed by mounting one twin roll caster on another twin roll caster. In this caster, the base strip is cast by the upper twin roll caster, and the overlay strips are cast by the lower caster. The three strips are metallurgically bonded by the lower caster. This study investigated three aspects of this caster. First, the clad ratio could be controlled by the solidification lengths of strips from the upper and lower twin roll casters, and a clad ratio of 1:8:1 was attained. Second, although it is known that fabrication of clad strips from Al-Mg alloy and other Al alloys is very difficult, the clad strip with the Al-Mg alloy as the base strip or the overlay strip could be cast. Finally, by adding scrapers, the caster could cast the clad strip with a base strip having a lower melting point than the overlay strip. Element strips of the clad strip are made by many processes, such as direct chill (DC) casting, scraping of the ingot surface, heat treatment, hot rolling, and cold rolling. Typically, surface treatment and hot rolling are used to clad the strips. Since many processes are required, clad strips require consume much energy. Therefore, producing clad strips is expensive. A vertical-type tandem twin roll caster was developed to cast clad strips. This caster has the advantages of process saving and energy saving, and so can fabricate economical clad strips. In the fabrication of clad strips, control of the clad ratio is very important. In the brazing sheet for automobile radiators, the base strip is made from AA3003 and the overlay strips are made from AA4045, and the clad ratio is usually 1:8:1. In the present study, a clad strip with a clad ratio of 1:8:1 was attained. The cladding by hot rolling of Al-Mg and other aluminum alloys, which is considered to be a very difficult process, was also investigated. Clad strips with either a base strip or an overlay strip of an Al-Mg alloy were cast by the roll caster. Although the cladding was not easy, the Al-Mg alloy could be cast into the clad strip. In addition, a clad strip with a base strip having a lower melting point than that of the overlay strip was investigated. Such cladding cannot be cast by the vertical-type tandem twin roll caster as mentioned above because the base strip is re-melted from the heat of the overlay strips. In the present study, a scraper was developed and adopted to cast a clad strip with a base having a lower melting point than that of the overlay strips. This type of clad strip could be cast because the scrapers prevented the re-melting of the base strip. In this paper, these three aspects of fabrication are reported.

Clad Strip Casting by a Roll Caster

Casting of clad strip, which was one of the composite alloys, was tried using a roll caster. A vertical tandem type twin roll casters for clad strip were designed and assembled to cast the clad strip. Three layers of clad strip could be cast. The interface between the base strip and overlay strip was clear. The as-cast clad strip could be cold rolled without peeling at the interface. The element of the each strip did not diffuse to another strip at the interface. The effects of the roll speed and melt temperature of the overlay strip on the cladding of the strip were investigated.

Clad Strip Casting Using a Twin Roll Casters

The three layers clad strip was fabricated by a vertical type tandem twin roll caster for clad strip (VTTCC). The effect of the casting conditions of the base strip and the overlay strip on the interface between the base strip and the overlay strip was investigated. The temperature of the molten metal and roll-load were investigated casting conditions. Base strip was AA8079 and overlay strip was AA6022. The proper melt temperature of the overlay strip was around the liquidus line of the base strip. The proper roll-load, which was smaller than rolling, was existed.

Casting of Clad Strip by a Roll Caster

The three layers clad strip was fabricated by a tandem positioned vertical type twin roll casters. The effect of the casting conditions of the overlay strip on the interface between the base strip and the overlay strip was investigated. The temperature of the molten metal, roll-load and solidification length were chosen as the casting conditions. Base strip was AA8079 and overlay strip was AA6022. The proper melt temperature of the overlay strip was above the liquidus line of the base strip. The proper roll-load, which was lower than rolling, was existed. There was not clearance at the interface when the solidification length was appropriate.

Roll Casting of Three Layers Clad Strip

A roll caster, which could cast the three layers of clad strip directly from the molten metal, was designed, assembled and tested. The base strip was AA3003 aluminum alloy and overlay strips were AA4045 aluminum alloy. An unequal diameter twin roll caster was modified to cast clad strip. Two small rolls were amounted on a large roll. A scraper plate was used to prevent the mixture of the different kinds of melts. The casting of three strips and the connecting of strips could be operated by one roll caster. The interfaces between the strips were clear, and the mixture of the melt did not occur. The clad strip could be cold rolled without the annealing. The clad strip did not peel at connecting surface by the cold rolling and continuous bending. The strips were connected strictly. The casting speed was 20m/min, and this speed was much higher than the casting speed of the conventional twin roll caster for aluminum alloys.

A twin-roll caster to cast clad strip

A single-roll caster and two kinds of twin-roll casters to cast clad strips were designed and assembled. One of twin-roll casters was suitable for clad strip casting. This twin-roll caster can cast clad strips of aluminum alloys at the speed of 20 m/min. The thickness of the clad strip is about 2.0 mm. The clad strip has a clear interface between the two strips. The clad strip is connected strongly at the interface. Therefore, the clad strip does not peel off at the interface after bending until broken. The clad ratio of the thickness between the overlay strip and the base strip is 2:1–1:10. An alloy with a melting point lower than that of the base strip is suitable for the overlay strip. The roll speed, cooling distance of the base strip, and the temperatures of the melt for the overlay strip are important factors in producing sound clad strips.

The open tension-free mesh repair of inguinal hernia Analysis of 1,235 cases

1235 outpatient repairs of inguinal hernias under local anesthesia with IV sedation were performed between September 1993 and June 1997. The average age was 63. Twelve percent were recurrent repairs. All indirect hernias and all focal diverticular type V direct defects were treated with a cone-shaped polypropylene plug plus an overlay mesh strip. All broad fusiform type IV direct defects were repaired either by the same plug method or in the manner of a Lichtenstein repair. Mortality was zero. There were 3 recurrences, 5 superficial hematomas, 5 seromas, 1 questionable neuralgia, 1 dysejaculation, 1 ischemie orchitis, 1 flare-up of gout and 1 TIA, for a complication rate of 1.46%. Infection rate was zero. Recurrence rate thus far is only 0.24%, 0.16% for primary repair and 0.67% for recurrent repair.