Surface heat treatment is a steel ball heat treatment process that only heats the surface layer of the workpiece to change its surface mechanical properties. In order to heat only the surface layer of the workpiece without excessive heat being introduced into the interior of the workpiece, the heat source used must have a high energy density, that is, to give a large amount of heat energy to the workpiece per unit area, so that the surface layer or local portion of the workpiece can be short-time or instantaneous. Reach high temperatures. The main methods of surface heat treatment include flame quenching and induction heating heat treatment, commonly used heat sources such as aerobic acetylene or oxypropane, induction current, laser and electron beam.
Chemical heat treatment is a steel ball heat treatment process that changes the chemical composition, structure and properties of the surface of the workpiece. The difference between chemical heat treatment and surface heat treatment is that the latter changes the chemical composition of the surface layer of the workpiece. Chemical heat treatment is to heat the workpiece in a medium (gas, liquid, solid) containing carbon, nitrogen or other alloying elements for a long time, so that the surface of the workpiece penetrates into carbon, nitrogen, boron and chromium. After infiltration of the elements, other heat treatment processes such as quenching and tempering are sometimes performed. The main methods of chemical heat treatment are carburizing, nitriding, and infiltration of steel balls.
Heat treatment is one of the important processes in the manufacturing process of mechanical parts and tooling. In general, it can guarantee and improve various properties of the workpiece, such as wear resistance and corrosion resistance. It also improves the microstructure and stress state of the blank to facilitate various cold and hot processing.
For example, white cast iron can be obtained by long-term annealing treatment to obtain malleable cast iron, which improves plasticity. The gears adopt the correct heat treatment process, and the service life can be increased by several times or several times than that of the gears without heat treatment. In addition, the inexpensive carbon steel passes through. Some alloying elements have some high-performance alloy steel properties, which can replace some heat-resistant steels and stainless steels; almost all of the tooling tools need to be heat treated before they can be used.
Classification of steel
Steel is an alloy containing iron and carbon as its main components, and its carbon content is generally less than 2.11%. Steel is an extremely important metal material in economic construction.
Steel is divided into two categories according to its chemical composition: carbon steel (carbon steel for short) and alloy steel. Carbon steel is an alloy obtained from the smelting of pig iron. In addition to iron and carbon as its main components, it also contains a small amount of impurities such as manganese, silicon, sulfur and phosphorus. Carbon steel has certain mechanical properties, good process performance and low price. Therefore, carbon steel has been widely used. However, with the rapid development of modern industry and science and technology, the performance of carbon steel can not fully meet the needs, so people have developed a variety of alloy steel. Alloy steel is a multi-component alloy obtained by preferentially adding certain elements (called alloying elements) on the basis of carbon steel. Compared with carbon steel, the performance of alloy steel is significantly improved, so it is increasingly used.
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A dumbwaiter is a small freight elevator or lift intended to carry objects rather than people. Dumbwaiters found within modern structures, including both commercial, public and private buildings, are often connected between multiple floors. When installed in restaurants, schools, kindergartens, hospitals, retirement homes or in private homes, the lifts generally terminate in a kitchen.
The term seems to have been popularized in the United States in the 1840s, after the model of earlier "dumbwaiters" now known as serving trays and lazy Susans. The mechanical dumbwaiter was invented by George W. Cannon, a New York City inventor. Cannon first filed for the patent of a brake system (US Patent no. 260776) that could be used for a dumbwaiter on January 6, 1883. Cannon later filed for the patent on the mechanical dumbwaiter (US Patent No. 361268) on February 17, 1887.Cannon reportedly generated a vast amount of royalties from the dumbwaiter patents until his death in 1897.
A simple dumbwaiter is a movable frame in a shaft, dropped by a rope on a pulley, guided by rails; most dumbwaiters have a shaft, cart, and capacity smaller than those of passenger elevators, usually 45 to 450 kg (100 to 1000 lbs.) Before electric motors were added in the 1920s, dumbwaiters were controlled manually by ropes on pulleys.
Early 20th-century codes sometimes required fireproof dumbwaiter walls and self-closing fireproof doors and mention features such as buttons to control movement between floors and locks on doors preventing them from opening unless the cart is stopped at that floor. Dumbwaiter Lifts in London were extremely popular in the houses of the rich and privileged. Maids would use them to deliver laundry to the laundry room from different rooms in the house. They negated the need to carry handfuls of dirty washing through the house, saving time and preventing injury.
A legal complaint about a Manhattan restaurant's dumbwaiter in 1915, which also mentions that food orders are shouted up and down the shaft, describes its operation and limitations as follows:
[There is] ... great play between the cart of the dumb-waiter and the guides on which it runs, with the result that the running of the cart is accompanied by a loud noise. The rope which operates the cart of the dumb-waiter runs in a wheel with a very shallow groove, so that the rope is liable to and does at times slip off. ... The cart has no shock absorbers at the top, so that when it strikes the top of the shaft or wheel there is a loud report. ... [T]he ropes of the dumb-waiter strike such wall at frequent intervals with a loud report. ... [T]he dumb-waiter is often negligently operated, by running it faster than necessary, and by letting it go down with a sudden fall.
More recent dumbwaiters can be more sophisticated, using electric motors, automatic control systems, and custom freight containers of other kinds of elevators. Recently constructed book lifts in libraries and mail or other freight transports in office towers may be larger than many dumbwaiters in public restaurants and private homes, supporting loads as heavy as 450 kg (990lbs)
Dumbwaiter Lifts, Service Lifts, Service Lift, Dumb Waiter, Dumbwaiter Lift
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