steel pipe fitting

Dec 21


Allice S Lee

Allice S Lee

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Introduce some basic knowledge of steel pipe fitting


Pipe Fittings knowledge A pipeline system:     You must use the elbow bend the pipe,steel pipe fitting Articles the pipe size to use adjustable head, forked: to transport liquid or gas, you must use a variety of channels, in addition to straight pipes with steel pipes, but also use all kinds of pipe fittings use a tee, use the pipe flange joints and fittings are connected, in order to achieve the purpose of open transmission medium, but also with a variety of valves, to reduce the impact of thermal expansion or shrinkage of the piping system vibration frequency, but also with the expansion Section. In addition, in the pipeline, as well as with a variety of instruments connected to various joints Q plug and so on. We used to be in the pipeline system and other accessories in addition to straight pipes collectively referred to as pipe fittings.Second metallic materials common sense:      Metal materials are on our daily lives and the most widely used industrial materials. It is mainly divided into steel, iron and non-ferrous metals and other categories, and one of the most widely used steel is the most common material, steel is the main ingredient is iron, and the rest is artificially added various alloying elements and impurities. It is because of these different varieties added alloying elements. A different number before the formation of a variety of steel, such as ordinary carbon steel, stainless steel, alloy steel, etc. In these added elements, the carbon C plays a very important role .  2.1 common chemical element in steel:   Various steels majority percentage of iron (Fe), other than the, typically contain several of the following elements (commonly referred to as the alloying elements in steel):C (carbon) Si (silicon) Mn (manganese) P (phosphorus) S (sulfur) andCr (chromium) Ni (Nickel) Mo (molybdenum) Ti (titanium) V (vanadium) and so on.In general, where P, S is an impurity component, the lower the better the quality of steel.

2.2 Classification of Steel: Steel added according to the different varieties of alloying elements, we can simply be divided into three categories of steel: carbon steel, alloy steel, stainless steel.

1. Carbon steel: an alloy element has only C, Si, Mn, P, S five kinds, which according to P, S impurity content level, is divided into carbon steel (P, S general ≤0.040%), and quality carbon steel (P, S general ≤0.03%), common steel grades are:             Carbon steel: Q215A Q235BF             Quality carbon steel: 20 # 45 # 16Mn etc.This steel strength and toughness in general, impatience corrosion, can be used in less demanding situations, the lowest cost.

2. Steel: In addition to five kinds of elements contained in steel, also added Cr 10% or less of Mo V and other elements, common steel grades: 15CrMo 12Cr1MoV 1Cr5Mo like.Compared with carbon steel, alloy steel, higher strength, heat resistance is also improved, but is still poor corrosion resistance, therefore, steel corrosion is not typically used for high temperature and pressure applications, such as boiler steel, thermal power plant steam delivery etc., the cost at a medium level

3. Stainless steel: carbon steel is usually based on the increase in the proportion of high Cr, Ni alloy is made, the content ratio of up to 20%. Common steel grades: 304, 304L, 321, 316,316L, 1Cr18Ni9Ti, steel front for several numerical Japan, the United States steel representation, the last one (1Cr18Ni9Ti) for domestic steel representation. The following numeric notation steel to illustrate the relationship between several stainless steel components: As a general understanding, but also easy for beginners to remember, we can not think so (but not quite accurate to say):            304 ...- basic steel species containing only (C <0.08%), Cr (~ 18%), Ni (~ 9%)            304 (C <0.05%) 304L ..- C is called ultra-low carbon 304L            321 ...- 304 + Ti (~ 0.5%)            316 ...- 304 + Mo (~ 2.5%)            Ultra-low carbon 316L ..- C of 316 (C <0.05%) called 316LStrength stainless steel, various steel toughness index is the best, the most outstanding advantage is anti-corrosion, chemical and paper corrosive occasions it is necessary to use stainless steel, of course, the cost is the highest.

Performance 2.3 Steel, said:    A steel performance is good or bad, always use some indicators to reflect, to represent. For steel, we usually use the chemical composition which contains numerical mechanical properties to reflect its quality and performance. Mechanical properties usually have three indicators:    Tensile strength (σb, TS): the material can withstand pull off the greatest external tension.Yield strength (σs, YS): plastically deformed material can withstand a minimum external tension.    Elongation (ψ, EL): fractured material, extending in the longitudinal direction of the percentage, the greater the value, the better the described plastic material. Sometimes, with hardness values, impact toughness values reflect the performance of other materials.Our most common carbon steel 20 #, Q235 and abroad SS400, SS41, St37, etc., their performance is very close, or that which can substitute for one another, their relevant parameters as follows:C: 0.18-0.21% Si: 0.30% Mn: 0.5% P, S 0.025%TS: ~ 550Mpa YS: ~ 260Mpa EL: ~ 25%

2.4 Steel organization and change:Why the difference in the performance of steel, in fact, the internal organizational structure of steel related. It can be seen through a microscope, the interior steel is composed of many different cells in the same small tranches as stacked together, and then carefully observed, these small tranches actually belong to several different categories, we usually use the same kind of small tranches described as a "phase" or of a "body." As we usually say austenitic, ferritic steels refers to the two most common organizational structure, which is two phases. A steel which contains phase, how much each phase proportion occupied, how phase morphology, which have a direct impact properties of the steel. That is, if the type of steel in phases, proportion, shape changes, the performance of the steel necessary to follow the changes. Then, what factors will lead these years changes? Obviously, changes in composition of the steel change will definitely affect the performance of the steel, and fixed for a certain kind of ingredients steels, such as 20 # steel, or 304L, when they are performed deformation processing, heat treatment, and its performance It will change. To sum up, the main factors affecting the properties of steel are: composition, deformation and temperature.

2.5 steel heat treatment:      In order to make some kind of steel to achieve the best performance we want, we must make certain internal organizational structure and stability of the structure of a stable state.     In many cases, we have to be subjected to heat treatment of steel. Because many of our products are processed from the deformation, deformation of steel by the above-mentioned, it is necessary to change the organizational structure, that is, the performance of steel on the change, and this change is often what we I do not want to, then we must take measures to eliminate heat treatment of these changes, restore the original characteristics of the steel. Of course, because we have other considerations other heat treatment methods.

2.6 steel representation:World steel representation as endless, but most represented by two methods: a class of its content alloy containing elements to represent a class to the value and strength of steel symbol to represent. E.g:20 # quality carbon steel carbon content represents about 0.20 per cent45 # quality carbon steel carbon content of about 0.45% of1Cr18Ni9Ti- represents the carbon content: 0.1%                        About Cr18%                        About Ni 9%                        Ti: containing little0Cr18Ni9- indicates a very low carbon content, ≤0.08%                        About 18% Cr                        About Ni 9%Q235 ..- represents the yield strength> 235MPA of carbon Steel

SS400.- represents tensile strength> 400MPA of quality carbon steel