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Casting Defects and Types of Casting Defects

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Definition of Casting Defects:  It is unwanted irregularities that appear in the casting during the metal casting process. There is the various reason or sources which is responsible for the defects in the cast metal. Here in this blog we will discuss all the major types of casting defects. Some of the defects produced may be neglected or tolerated and some are not acceptable, it must be eliminated for better functioning of the parts.  TYPES OF CASTING DEFECTS  1. Gas Porosity:  Blowholes, open holes, pinholes 2. Shrinkage defects:  shrinkage cavity 3. Mold material defects:   Cut and washes, swell, drops, metal penetration, rat tail 4. Pouring metal defects:   Cold shut, misrun, slag inclusion 5. Metallurgical defects:   Hot tears, hot spot. 1. Shift or Mismatch:  The defect caused due to misalignment of the upper and lower part of the casting and misplacement of the core at the parting line. Cause : (1)  Improper alignment of upper and lower part during mold preparation.

Moulding Sand - Types of Properties and its Classification

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  Definition of  Moulding Sand : The principal raw material used in molding is molding sand because it provides several major characteristics that may not be obtained from other materials. Moulding sand is defined as granular particles resulting from the breakdown of rocks, due to the action of natural forces, such as frost, wind, rain, heat and water currents. Rocks have a complex composition and sand contains most of the elements of the rocks. Due to this reason, moulding sand differs considerably in different parts of the world. In nature, it is found on the bottom and banks of rivers and lakes. Moulding sand is classified into different categories according to the nature of its origin. Moulding is a process of making a cavity or mold out of the sand by means of a pattern. The molten metal is poured into the molds to produce the casting. Properties of molding sand. 1: Porosity or permeability It is the property of sand that permits the steam and other gases to pass through the sand

Current Affairs in One Minute 10 February 2021

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1-The prestigious Akashvani Music Festival has been renamed after Bharat Ratna Pandit Bhimsen Joshi, Information and Broadcasting Minister Prakash Javadekar announced.  सूचना प्रसारण मंत्री प्रकाश जावड़ेकर ने घोषणा की कि प्रतिष्ठित आकाशवाणी संगीत समारोह का नाम भारत रत्न पंडित भीमसेन जोशी के नाम पर रखा जाएगा।

Achyranthes Aspera (Apamarga) - Achyra-Aspe

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Introduction: - The use of Achyranthes Aspera is beneficial for curing many symptoms as: excessive urination, diarrhea, astringent, dysentery, dysmenorrhoea (painful menstruations) and the poisons of dog and snakes.  Achyranthes Aspera plant and seeds are rich in carbohydrates, proteins and certain constituents such as flavonoids, tannins, saponins that help maintain the overall health of an individual. According to Ayurveda, taking Achyranthes Aspera powder with honey helps improve digestion due to its Deepan (appetizer) and Pachan (digestive) properties. Regular consumption of a handful of Achyranthes Aspera seeds helps manage weight by reducing excess fat accumulation which results in the reduction of body weight. Directly applying the juice of Achyranthes Aspera leaves at the affected area might help in wound healing due to its astringent and anti-inflammatory. It can also be used to provide relief from ulcers due to its anti-ulcer and gastroprotective activity. It is a

Pattern- Making, Allowances and its Types of Pattern

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A pattern may be defined as a model of the desired casting which when molded in sand forms an impression called mold. The mold when filled with the molten metal forms casting after solidification of the poured metal. The quality and accuracy of casting depend upon the pattern making. The pattern may be made of wood, metal(cast iron, brass, aluminum, and alloy steel.), plaster, plastics, and wax.   Pattern Allowances: A pattern is always made larger than the required size of the casting considering the various allowances. These are the allowances that are usually provided in a pattern. 1: shrinkage or contraction allowance: The various metals used for casting contract after solidification in the mold. Since the contraction is different for different materials, therefore it will also differ with the form or type of metal. 2: Draft allowance It is a taper that is given to all the vertical walls of the pattern for easy and clean withdraw of the pattern from the sand without dam

Electric Resistance Welding

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Electric Resistance Welding It is a type of pressure welding. It is used for joining pieces of sheet metal or wire. The welding heat is obtained at the location of the desired weld by the electrical resistance through the metal pieces to a relatively short duration, low voltage, high ampere electric current. The amount of current can be regulated by changing the primary turns of the transformer. When the area to be welded is sufficiently heated, the pressure varying from 25MPa to 55MPa is applied to the joining area by suitable electrodes until the weld is solid. 

Arc Welding and its Different Processes

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Arc Welding: Arc welding is a fusion welding process in which the welding heat is obtained from an electric arc struck between the work(or base metal) and an electrode. The temperature of the heat produced by the electric arc is of the order of 6000°C to 7000°C. Both the direct current (D.C) and alternating current(A.C) may be used for arc welding, but the direct current is preferred for most purposes. When the work is connected to the positive terminal of the D.C welding machine and the negative terminal to an electrode holder, the welding set up is said to have straight polarity. On the other hand, when work is connected to negative and the electrode to a positive terminal, then the welding set up is said to have reversed polarity. The straight polarity is preferable for some welds while for other welds reversed polarity should be used.