Steel, roughness value

Thus, if we were to use the same pipe material (commercial steel) for the model as in the field, we would also have to use the same diameter (48 in.). This is obviously not practical, but a smaller diameter for the model would obviously require a much smoother material in the lab (because Dm -C Df requires em drawn tubing such as copper or stainless steel, all of which have equivalent roughness values of the order of 0.00006 in. (see Table 6-1). 

Most thin-film processes require a steel surface of high quality. Oil- or water-based polishing processes have been developed to obtain high quality surface finishes. Roughness values Ra below 10 nm can be achieved. 

What steel and brass compositions and what surface roughness values were used for the discs ... 

The steel disc was made of plain carbon steel with about 0.2% carbon in it. The composition of brass was about 70% Cu and 30% Zn. The arithmetic average surface roughness values for glass and brass disc surfaces were 0.006 ym and 0.08 Pm, respectively. The roughness parameters for the steel disc surfaces are given in the table below. 

The effect of different pressing forces of DP and RB processes on the mean roughness of low-, medium-, and high-carbon steel is shown in Figures 7.4 and 7.5. The initial average surface roughness values (Rj) were 0.9, 0.6, and 0.56 mm for the three steels, respectively (see Table 7.2). 

The RMS roughness values for steel ball and silica disk used for MTM are 11 and 2 nm, respectively (obtained from PCS instruments) and those for the steel ball and glass... 

If better surface roughness and geometrical accuracy is required, such as for mirror gloss surfaces roughness values of about 0.1 p and for optical purposes when 0.04 p is necessary, lapping can be used for normal steel grades to flatten the surface. 

Commercially provided 25.4 mm diameter steel balls of two different roughness values were employed in this study. The balls have no preferential surface roughness pattern. The glass disc has 150 mm in diameter and its surface is optically smooth. The silicon dioxide spacer layer about 195 nm thick covers almost entire underside of the glass disc with the exception of a narrow radial strip where only chromium layer is deposited. Scanning probe microscopy examinations of silicon dioxide films shows that they are extremely smooth [14]. Material properties of the contact bodies are summarised in Table 1. The surface roughness parameters of steel balls measured by stylus technique are given in Table 2. 

The most important displacive transformation is the one that happens in carbon steels. If you take a piece of 0.8% carbon steel "off the shelf" and measure its mechanical properties you will find, roughly, the values of hardness, tensile strength and ductility given in Table 8.1. But if you test a piece that has been heated to red heat and then quenched into cold water, you will find a dramatic increase in hardness (4 times or more), and a big decrease in ductility (it is practically zero) (Table 8.1). 

The relative roughness is expressed as E D, where E = the surface roughness and D = the internal pipe diameter. Typical values of E D are 0.0015 for drawn tubing, 0.046 for commercial steel and 0.12 for asphalted cast iron. 

These values are roughly constant across a range of electrolyte environments except where noted but the variations between alloys, heat treatment conditions, etc. creates a range for each metal. For some metals such as iron and steel the range is low ( 100 mV), but for lead, nickel, stainless steels a range is given. The corrosion potential is reported with respect to the saturated calomel reference electrode. 

Li et al. (2003) studied the flow in a stainless steel micro-tube with the diameter of 128.76-179.8 jm and relative roughness of about 3-4%. The Poiseuille number for tubes with diameter 128.76 and 171.8 jm exceeded the value of Po corresponding to conventional theory by 37 and 15%, respectively. The critical value of the Reynolds number was close to 2,000 for 136.5 and 179.8 pm micro-tubes and about 1,700 for micro-tube with diameter 128.76 pm. 

Spherical rollers were machined from AISI 52100 steel, hardened to a Rockwell hardness of Rc 60 and manually polished with diamond paste to RMS surface roughness of 5 nm. Two glass disks with a different thickness of the silica spacer layer are used. For thin film colorimetric interferometry, a spacer layer about 190 nm thick is employed whereas FECO interferometry requires a thicker spacer layer, approximately 500 nm. In both cases, the layer was deposited by the reactive electron beam evaporation process and it covers the entire underside of the glass disk with the exception of a narrow radial strip. The refractive index of the spacer layer was determined by reflection spectroscopy and its value for a wavelength of 550 nm is 1.47. 

An alternative to the measurement of the dimensions of the indentation by means of a microscope is the direct reading method, of which the Rockwell method is an example. The Rockwell hardness is based on indentation into the sample under the action of two consecutively applied loads - a minor load (initial) and a standardised major load (final). In order to eliminate zero error and possible surface effects due to roughness or scale, the initial or minor load is first applied and produce an initial indentation. The Rockwell hardness is based on the increment in the indentation depth produced by the major load over that produced by the minor load. Rockwell hardness scales are divided into a number of groups, each one of these corresponding to a specified penetrator and a specified value of the major load. The different combinations are designated by different subscripts used to express the Rockwell hardness number. Thus, when the test is performed with 150 kg load and a diamond cone indentor, the resulting hardness number is called the Rockwell C (Rc) hardness. If the applied load is 100 kg and the indentor used is a 1.58 mm diameter hardened steel ball, a Rockwell B (RB) hardness number is obtained. The facts that the dial has several scales and that different indentation tools can be filled, enable Rockwell machine to be used equally well for hard and soft materials and for small and thin specimens. Rockwell hardness number is dimensionless. The test is easy to carry out and rapidly accomplished. As a result it is used widely in industrial applications, particularly in quality situations. 

Effect of surface conditions While the value of the CHF is assumed not to be significantly affected by variation in heating surface roughness for ordinary liquids, some experiments with boiling liquid metals (cesium) on horizontal 0.43-in. (ll-mm)-diameter stainless steel-clad cylindrical heaters of three different surface types (Kutateladze et al., 1973 Avksentyuk and Mamontova, 1973) showed different magnitudes and kinds of crisis. These experimenters tested three types of surfaces ... 

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