Rockwell Hardness Number Research Articles

ロックウェル・クオータロード硬さ試験について(第1報)

The methods of Rockwell and Rockwell superficial hardness tests have practical advantages of getting the hardness number with a small personal error and of making easily the testing procedure automatic, because the hardness number is directly shown on the indicator. The methods of Rockwell quarter load and Rockwell quarter load superficial hardness tests are proposed in order to apply these advantages to test a small or thin specimen. As compared with the usual methods, the indenters of half size and a quarter amount of the loads are applied, and then the coefficients of the depth of indentation in the calculation formulas for hardness number are made twice. Even if the test load is changed, the same Rockwell hardness number is obtained when the indentation is geometrically similar under the condition where the ratio of the load to square amount of the size of the indenter is constant. To confirm this theory of similarity in hardness by experiment, the Rockwell and Rockwell superficial hardness testing machines and respective quarter load machines are produced. The errors of these machines' elements are integrated in HRB or HR 30 T as follows : their algebraic sums are within -0.5-0.3, and the roots of the sum of their squares are lower than 0.3.

Study on Loading Conditions of Rockwell Hardness Testers Commonly Used for C Scale

It is well known that the Rockwell hardness testers are suited to measure quickly the hardness of metals. But, because the Rockwell hardness test is static, the load is better to be applied until every indentation deforms completely. And the speed of the load application must be so slow that the inertia force of the moving parts may not affect the hardness numbers measured. The object of this research is to investigate the influence of the loading conditions of the major load on the Rockwell hardness numbers (HRC) measured by the Rockwell hardness testers commonly used in our country. As the result, the law of similarity for selecting the loading conditions was found. And, for its application, the author proposes the method of selecting the applying time and the keeping time of the major load in the HRC measurement.

On the Errors of Rockwell Hardness Number : 5th Reprot, Case of a Steel Ball of Large Diameter

On the Errors of Rockwell Hardness Number : 5th Reprot, Case of a Steel Ball of Large Diameter

On the Errors Introduced into Rockwell Hardness Number

On the Errors Introduced into Rockwell Hardness Number

On the Errors of Rockwell Hardness Number : 3rd Report, The Effect of the Error of Steel Ball Diameter

On the error introduced into Rockwell hardness numbers by the error of steel ball diameters, this paper reports the results of experiment and the caluculated results from Meyer's law. Results obtained by observation and theoretical calculation respectively coincided well with each other. Accordingly, the errors caused by the errors of total load W2 kg, preliminary load W1 kg and diameter D mm are shown as follows : [numerical formula].

On the Errors of Rockwell Hardness Number : 2nd Report, The Effect of the Form of Diamond Indentor

Regarding the error introduced into Rockwell hardness numbers by the error of form of diamond indentor, this paper reports the results of experiment and the calculated results from Meyer's law. Results obtained by observation and theoretical calculation respectively coincided well with each other. The errors resulted from the errors in the total load W2 kg, the preliminary load W1 kg (see the first report), the tip radius R mm and the angle of cone θ (rad) of diamond indentor will be as follows : [numerical formula]

プラスチックスのかたさおよび膨張率の温度依存性について

The author has inquired experimentally into the effect of the temperature ranging between 20°C and 200°C upon the Rockwell hardness and the thermal expansion behavior of several virgin plasticses after casting, such as phenolic, urea, melamine, polyester, epoxy, nylon 6, polypropylene, polytrifluoroethylene and polytetrafluoroethylene.Generally, the hardness of plastics goes down gradually as temperature rises and drops suddenly at a special temperature region, which nearly corresponds with the deflexion point in thermal linear expansion-temperature curve. The hardness is somewhat recovered again when the temperature surpasses this discontinuous point.The thermoplastic plasticses have generally lower values and more sensitive temperature dependence in Rockwell hardness number as compared with the thermosetting plasticses.The thermosetting plasticses, which contain the filler having more durability against high temperature than the resin itself, show lower temperature dependence for hardness, and a little amount of drop in hardness number at the discontinuous point as compared with the plastics having no filler.

On the Errors of Rockwell Hardness Number : 1st Report, The Effect of the Errors of Testing Load

This paper is a part of the continued study on the errors of measurement of Rockwell hardness number and reports the results of experiment and the caluculated results from Meyer's law to find the effect of the errors of preliminary and total loads. Both results obtained by observation and theoretical calculation respectively coincided very well with each other. The errors due to the error in the total load W2 and the preliminary load W1 are given as follows : [numerical formula] and [numerical formula].

プラスチックスのロックウエル硬さにおける押込み加圧時間と除圧後の時間の影響について

The authors have inquired experimentally into the effects of the times of impressing the specimen and after unloading upon the Rockwell hardness numbers for plastics and steel.The experiments have been carried out under the constant impressive load, 150kg, using the constant indentor, 1/4 inch steel ball. The materials of specimens tested are a soft steel and the five kinds of plastics, such as phenolic, urea, polyester, polystyrene and nylon.As the results, two empirical formulas have been derived as follows: HR=H1-ΔH0·(logt)m (1) and HR=(H1-k·logt)+(n1+l·logt){log(logt')} (2) where HR is the total depth of indented hole under impressive loading in the scale of Rockwell hardness numbers, H1 hardness numbers at impressive loading instant, ΔH0 hardness numers' changes from H1 to 10sec impressive loading's, HR Rockwell hardness numbers, t duration of impressive loading, t' time after unloading, and H1, k, l, m and n1 are the constants proper to the materials.Accordingly, the Rockwell hardness numbers HR1 for the standard duration of impressive loading t1 and time after unloading t'1 may be obtained by the following formula HR1=HR+k·logt/t1+n1·log(logt'1/logt')+l·{logt1·log(logt'1)-logt·log(logt')} (3) where HR is the Rockwell hardness numbers of the material for any duration of impressive loading t and time after unloading t'.

The Effects of the Roughness of the Testing Surface and of the Reverse Surface of the Specimen on the Vickers Hardness

In this report, at first, the of the roughness of the testing surface of on the Rockwell hardness was investigated, and then the of the roughness of the reverse surface was investigated, after the experiment on many specimens which were of different hardness or material. As a result, these effects on the Rockwell hardness number have been made clear, and it has been revealed that the roughness of the testing surface of affects the hardness number, but on the other hand the roughness of the reverse surface does not influence the hardness number. The critical roughness curve which shows the relation between the surface condition ranging from the maximum (critical) roughness for the testing surface to free-from-the-effect of the roughness and the hardness of was given. And after discussion of this result, it was presumed that the so-called effect of the roughness of the reverse surface of specimen which is told to be existed in industrial measuring is not due to the roughness itself but to the more direct causes related to the condition of the reverse surface. And also, the effects on three hardnesses, the Shore, Vickers and Rockwell, which are most widely used nowadays, were compared in this report.

歯科用切削工具の切削性に関する研究 (第3報)

The life of machinability of commercial round type burs produced in Japan, Germany, America and Denmark were measured by vertical drilling methylmethacryllic resin blocks and aluminium: alloy plate reciprocally. Aluminium alloy plate has the Rockwell hardness number 84.0 to 88.2 in B; scale and 3 mm thickness.From results of this work, this report might be concluded as follows.1. Relation between thrust (T) and number of drilling of Al-alloy plates (N) is classified as follows.i) The more N increases, the more T increases gradually.ii) As N increases, T increases extremely periodically. This type burs' lives are bad.iii) T increases parabolically as N increases. This type burs indicate not so good lives.2. From the minimum N giving be the product of initial thrust Ti and arbitrary constant K, the degree of fall of machinability can be compared with.3. From the microscopic inspection, the form of blades are classified as follows, i) No changes are observed.ii) Dull of the edges are observed partially.iii) Dull and wear of the blades and edges are observed in all.4. There is no relation between the initial thrust and life.

高炭素鋼の恒温焼鈍について

High Carbon steel (1.5%C) used in file making shows Rockwell hardness number HRC 46∼48 at hot rolled condition, but to make the next works easy, it must be softened down to HRC 20∼23. We intended to adopt isothermal annealing for this purpose. The present experiment has been carried out to aquire some practical data for isothermal annealing of the steel; for instance, the effects of annealing temperature (denoted by T1, which is higher than Ar1 transformation temperature) and annealing time, the effects of holding temperature (denoted by T2, which is lower than Ar1) and its time, on the Rockwell hardness number. The results led to the following conclusion:—The annealing temperature T1=800∼850° (1 hr) and the holding temperature T2=650∼700° (1∼1.5 hr) are found to be applied for our purpose.

A theory of rockwell ball hardness

A theoretical analysis of the Rockwell method of ball hardness measurements is made. A general expression for Rockwell ball hardness numbers in terms of the Meyer constantsn andb is given. It is shown that the theoretical results are in agreement with experimental results. The conversion of Meyer and Brinell hardness numbers to Rockwell hardness numbers is discussed.

Theory of Hardness and Measurements Applicable to Contact Problems

The theory of the hardness is reviewed and measurements are made with respect to the application of hardness data to contact problems, particularly for the determination of the real contact area. The ball indentation method is recommended, with hardness H defined as the ratio P/Sm between the contact load P and the mouth area Sm of the indentation. This hardness is not a single valued material constant but is a function of the specific depth D of the indentation, where D is the ratio between the actual depth and the radius of curvature of the indentation. The variation of H with geometric and metallurgical conditions is discussed together with some empirical formulae to describe the experimental results. The relation between the hardness and the yield point is discussed. A comparison with Brinell and Rockwell hardness numbers is also made. The indentation which two crossed cylindrical rods produce in each other is found to give nearly the same hardness as the ball indentation tests if D exceeds a certain value.

The Testing of Metallic Materials

THE Rockwell hardness number is based on the additional depth to which the penetrator is driven by a heavy load beyond the depth to which the same penetrator has been driven by a definite light load. A minor load is applied and often, without moving the specimen, a major load is applied. The major load is then removed leaving the minor load on, and the hardness number is indicated on the dial.