Rockwell B hardness

The as-cast metal produced from electrolytic powder has a Rockwell B hardness of 80-83 (Brinell Hardness Number 150 5). 

The test is conducted in the following manner 200 mg of hexogen are press-loaded at 1115 kp/cm in a polymethylmetacrylate (PMMA) holder. Above it, a primary explosive is filled in the state at which its initiating strength is to be tested freely poured or pressed to a desired density. The initiation of the primary explosive is performed by means of a safety fuse. If the depth of the dent produced after initiation in the steel witness plate of 70-90 Rockwell B hardness is greater than 0.76 mm, the complete detonation of hexogen is... 

CPT Critical pitting temperature HRB Rockwell B hardness number... 

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. 

Other methods of determining the hardness of a material include a variety of "penetration" tests that yield hardness values measured in scales known as the Brinell, Rockwell (B or C), and scleroscope scales. These scales provide reliable hardness values for most materials, including ceramics, glass, metals and alloys, and wood (see Table 21). Unfortunately, as can be seen in the table, the various tests provide somewhat different hardness values for the same materials. 

The A, D, and C Rockwell scales used primarily for steel and hard materials yield hardness numbers from 20 to about 85. Hardness numbers lower than HRC 20 are invalid the Rockwell B, G, or F scales should be used. Hardness conversions from one scale to another are available for some common... 

Fig. 1. Ultimate tensile strength, MPa vs hardness. Rockwell B, A Rockwell C, Brinell, O and Vickers, x. To convert MPa to psi, multiply by 145.

MR0175, For carbon steeft the hardness limit shoiid be 200 Srlneil Rockwell B 95 see NACE Standard RP0472) p4] Avoid use of cement linings or Monel 400 for sour water. See Number 14 for corrosion allowance on carbon steel exposed to sour water. 

Figure 10.23 Hardness indenters (a) Brinell steel or tungsten carbide sphere (b) Rockwell A, C, D diamond cone (c) Rockwell B, F, G steel sphere (d) Vickers diamond pyramid and (e) Knoop diamond pyramid...

Other common hardness tests involve the use of diamond pyramids. In the Vickers hardness test, a square pyramid is used and in the Knoop hardness test, the pyramid is elongated. The area term in the former test is the actual indentation area and in the latter, the projected area. From the impression geometries, shown in Fig. 6.30, the Vickers Hardness Number (VHN) and Knoop Hardness Number (KHN) can be shown to be VHN=1.854F/a and KHN=14.2F/L, respectively. A common hardness test in the USA is the RockweO hardness test, which uses various indenter types and loads. The result of these tests is a dimensionless number and leads to the use of various hardness scales (e.g., Rockwell B, Rockwell C). 

Tube wastage will often be evident and manifested as flat spots on either side of the upstream of flue gas flow, as can be seen in Figure 3.6a. A ring sample (Figure 3.6b) was sectioned from the tube for dimensional and hardness measurements. The tube had thinned significantly at two positions due to coal ash corrosion. The thinnest section of the ring (0.291 in. at the 8 00 position) was at 88% of MWT. The hardness, averaging 73 Rockwell B (RB), showed that the tube had softened after 23 years of service. 

The stainless steel designations are those of the American Iron and Steel Institute. The composition of most of the other materials is listed in Engineering Alloys [23] and those not so listed are included in Table 5-2. All the materials were tested in the annealed condition except in the cases where parentheses follow the alloy designation, in Table 5-3. The number thus enclosed is the hardness of the material on either the Rockwell C (RC) or Rockwell B (RB) scale. 

Procedure B of the Rockwell R hardness test (ASTM D785) applies to plastics. The load on a 0.5 in (1.3 cm) indenter is held for 10 s at 10 kg and then increased... 

Vickers and Knoop indentors, Barcol hardness, and Shore durometers (2) (b) to measure the resistance of a material to scratching by another material or by a sharp point, such as the Bierbaum hardness or scratch-resistance test and the Moh one for hardness and (c) to measure rebound efficiency or resilience, such as the various Rockwell hardness tests. The various tests provide different behavior characteristics for plastics, as described by different ASTM standards such as D 785. The ASTM and other sources provide different degrees of comparison for some of these tests. 

The research objective has been to define the durability of a coating depending on mixture composition Ni-Cr-B. Besides, one had to determine the optimal composition of the given three-component mixture. Since there is a linear correlation between resistance on wear-out and hardness of coating, Rockwell hardness (HRC) has been chosen as the system response. Based on preliminary information, it is known that the response surface is smooth and continuous. Hence, it may be... 

The standard test methods for determining Rockwell hardness are listed in Table 12.6 and the Rockwell scales are given in Table 12.7. For example, ISO 2039 employs a hardened steel ball, 5 mm diameter. The ball is pressed into the specimen under a specified load selected to give an indentation between 0.07 and 0.10 mm (Method A) or between 0.15 and 0.35 mm (Method B). The recommended thickness of the specimen is 4 mm and the suggested time of application of the load is 30 s before the depth reading is taken. 

There are four major indentation hardness tests, which differ from each other in the shape of the indenter (Figure 10.23). The first of these, described in 1900, was the Brinell test, using a 10 mm steel ball indenter (Figure 10.23a), giving the Brinell hardness number, BHN. This was suitable only for metals softer than steel. In 1920 Rockwell developed a number of tests, including the B, E, F and G scales, in which the indenter is steel, and the A, C and D scales, using a conical diamond indenter with a spherical tip (Figures 10.23b and 10.23c). In the Rockwell test the difference in size between the... 

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