Quality is Our Priority
For the past five decades, we have worked hard to make sure that while our customers get bright bar products at the most competitive prices, there is no compromise made in quality. Our dedicated team at Dhand Steels is committed to delivering quality at all stages. Inspections in quality start right from the procurement of raw materials till the delivery of finished goods. We also make sure that besides testing and quality checks throughout the implementation process, we provide our customers with prompt post-sales services.
- Inspection of Raw Material: The raw material is tested and checked before initiating the production for chemical properties and surface defects.
- In-Process Inspection: Our team of quality control supervisors ensures that attributes like tolerance, length, straightness, and surface finish are checked and maintained during different phases of the production cycle.
- Inspection of Finished Products: During this stage, the products are checked for finishing, packaging, color coding, marking, chemical and mechanical properties, corrosion, etc. This is to make sure that the finished products comply with the requirements of the customer. We implement several highly-efficient testing methods to check for the chemical and mechanical properties of steel. Below-mentioned is a comprehensive list of all the types of testing that is performed at Dhand Steels to ensure that customers are delivered a defect-free product.
Types of Testing
A simple uniaxial test or compression test does not always provide adequate information. Instead, when a sample is tested against bends and flexes, it experiences an intricate amalgamation of forces like tension, shear, and compression. The testing equipment simulates a loading condition that is similar to real-life. Our engineers rely on this test to study the material’s behavior and accordingly, look for alternatives to resolve the shortcomings in consistency which get highlighted through the test.
To perform bend testing, the primary requirement is the correct equipment. The bend test has two convex sides and a concave top. So, when the specimen is placed in between the equipment, the convex side produces tensile stress and the concave top compresses the material. In this process, an area of shear stress is created along the midline. Initially, the shear stress is controlled by managing the span to depth ratio. This step helps in ensuring that if there are any primary faults from the tensile or compress stress, they can be identified easily. In most cases, a defect over 3mm in length is the threshold value for rejection of the specimen for further use.
Hardness is often considered to be a physical property of steel. However, what most people don’t know, is that hardness is a characteristic. It has been defined as the resistance to indentation. It is especially considered for materials like steel and its alloys.
To test the hardness of a material, the ASTM E0 and ISO 6506 standards have defined the Brinell Hardness Test.
The Brinell Hardness test is an effective method for evaluating the resistant properties of a material to applied forces for a specific period. The equipment comprises a spherical tungsten carbide indenter, the specimen, a timer, and a constant load of force ranging between 1838.7469N to 29419.95 N.
The indenter is placed on the specimen and the constant force is applied for a minimum of two seconds to a maximum of eight seconds. If the time is increased further, it is mentioned in the calculation of the test. Once the time is over, the indenter is removed from the specimen’s surface and the residual indentation is measured by taking the arithmetic mean of the two perpendicular diagonals. If the indentation left is large, it means that the material is softer than initially anticipated.
Just like the Brinell Hardness Test, the Rockwell Hardness test, too, implements the indentation manner of testing. The difference between the two tests lies in the higher accuracy and versatility of the Rockwell Hardness test. The ASTM E-18 standard has defined this test and it is the most common method of hardness testing.
In this test, different loads are applied to the indenter to check the permanent depth of indentation that is produced on the specimen’s surface. The indenter is generally a diamond or a spherical ball that is placed over the surface before the application of the minor load.
The minor load ranges from 29.4199N to 98.0665N. This load breaks through the surface to ensure that the surface finish does not hamper with the hardness results obtained. After a specific period, the load is removed and the depth of the indentation is measured.
Once this minor load or ‘preload’ is removed, an additional load is added to reach the optimum test load, which ranges between 147.1N and 1471N. This additional force is held to the surface to give time for the elastic recovery of the material. After the removal of this major load, the depth of the indentation is measured again. The Rockwell hardness values are the difference between the two depths of indentation measured. The distance is converted into a hardness number.
The Brinell hardness number is expressed as the ratio of the load to the measured area of indentation while the Rockwell hardness number is the difference in the depth of the indentation measured by applying two different forces.
Ultrasonic testing is widely-applied in the manufacturing of metals. This testing method uses high-frequency sounds to locate cracks, crevices, and other hidden defects. The fault analysis of this testing method is highly accurate and reliable.
Some of the defects that are accurately identified by this test are:
- Corrosion
- Pitting
- Erosion
- Cracks
- Abrasions
- Holes
- Honeycombs
The test also helps in inspecting the irregularities in the wall thickness and the surface coating.
The ultrasound probe is connected to its diagnostic machine. It, then, passes over the specimen for inspection and emits high-frequency sound waves. The presence of any irregularity or defect causes the remission of the sound energy which is then detected by the machine. Both immersion and contact methods of testing are available. However, analysts have found that the immersion method is more accurate and faster when compared to the contact method of testing. It also eliminates the need for direct contact, which in turn, ensures that the external factors are almost null.
The sound frequencies range from 2MHz to 10MHz. Cracks, piping voids, or inclusions are generally tested for solid bars. In tubular products, cracks and porosity are two common defects that are identified. With the advancement of technology, the Ultrasound Testing has been extended to manual, automated, and phased array types, which have proven to be more effective.
Steel is one of the major metals that dominate the manufacturing industry, as it has a wide range of applications. The Steel Industry in India accounts for 2% of the GDP. Therefore, the production of steel requires high precision and accuracy. The Magnetic-Particle testing helps in detecting linear flaws that are located at or near the surface of steel and other ferromagnetic materials like, Copper and Nickel, which too, find their extensive use in the Industries.
This method of inspection is very effective in exposing the surface faults like surface breaking, cracking, pores, cold lap, and lack of sidewall fusion in welds. The common technique of carrying out this test is by painting the specimen with white paint that can be stripped off after use, magnetizing the area with a yoke magnet, and then using a magnetic ink that is composed of iron powder particles to identify the areas of deformities. The electromagnetic yoke magnet has a power of 110v AC. The thickness of the paint should not be more than 0.005”.
The visual Testing method uses optical instruments to detect any present discontinuities on the surface of the steel. The magnification power of more than 10x allows the tester or analyst to identify any deviation of size and shape other than the specified allowed values.
Any unwanted particles on the surface of the materials are removed before placing the specimen under scrutiny as rust, scale, oil, dirt, paint, metal spray, and other such impurities can tamper with the obtained results. The visual testing method is the most commonly employed test. It does not require additional power equipment, and it also leads to quick identification of defects.
ISO Tolerance
As you may know, in the steel industry, each product has certain defined dimensions and sizes. And, for each size of product, there will be some standard tolerance requirements. Below-mentioned in the post are the different bright bar tolerance requirements between BS 970-3 and ISO 286-2 standard.
Tolerances classes
Tolerances on dimensions, (diameter, thickness, width), are those established by ISO 286-2. The tolerances shown in this tables-below are normally applied to metric sizes of drawn bright steel bars.
| Nominal Dimension | Tolerance Zone in mm (External Measurements) |
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|---|---|---|---|---|---|---|---|---|---|---|
| over | to | m6 | h6 | h8 | h10 | h11 | h13 | h14 | h15 | h16 |
| 0 | 1 | +0.002 +0.008 | 0 -0.006 | 0 -0.014 | 0 -0.040 | 0 -0.060 | 0 -0.14 | |||
| 1 | 3 | +0.002 +0.008 | 0 -0.006 | 0 -0.014 | 0 -0.040 | 0 -0.060 | 0 -0.14 | 0 -0.25 | 0 -0.40 | 0 -0.60 |
| 3 | 6 | +0.004 +0.012 | 0 -0.008 | 0 -0.018 | 0 -0.048 | 0 -0.075 | 0 -0.18 | 0 -0.30 | 0 -0.48 | 0 -0.75 |
| 6 | 10 | +0.006 +0.015 | 0 -0.009 | 0 -0.022 | 0 -0.058 | 0 -0.090 | 0 -0.22 | 0 -0.36 | 0 -0.58 | 0 -0.90 |
| 10 | 18 | +0.007 +0.018 | 0 -0.011 | 0 -0.027 | 0 -0.070 | 0 -0.110 | 0 -0.27 | 0 -0.43 | 0 -0.70 | 0 -1.10 |
| 18 | 30 | +0.008 +0.021 | 0 -0.030 | 0 -0.033 | 0 -0.084 | 0 -0.130 | 0 -0.33 | 0 -0.52 | 0 -0.84 | 0 -1.30 |
| 30 | 50 | 0 -0.39 | 0 -0.62 | 0 -1.00 | 0 -1.60 |
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| 50 | 80 | 0 -0.46 | 0 -0.74 | 0 -1.20 | 0 -1.90 |
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| 80 | 120 | 0 -0.54 | 0 -0.87 | 0 -1.40 | 0 -2.20 |
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| Nominal Dimension | Tolerance Zone in mm (Internal Measurements) |
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|---|---|---|---|---|---|---|---|
| over | to | H7 | H8 | H9 | H11 | H13 | H14 |
| 0 | 1 | +0.010 0 | +0.014 0 | +0.025 0 | +0.060 0 | +0.14 0 | |
| 1 | 3 | +0.010 0 | +0.014 0 | +0.025 0 | +0.060 0 | +0.14 0 | +0.25 0 |
| 3 | 6 | +0.012 0 | +0.018 0 | +0.030 0 | +0.075 0 | +0.18 0 | +0.30 0 |
| 6 | 10 | +0.015 0 | +0.022 0 | +0.036 0 | +0.090 0 | +0.22 0 | +0.36 0 |
| 10 | 18 | +0.018 0 | +0.027 0 | +0.043 0 | +0.110 0 | +0.27 0 | +0.43 0 |
| 18 | 30 | +0.021 0 | +0.033 0 | +0.052 0 | +0.130 0 | +0.33 0 | +0.52 0 |
| 30 | 50 | +0.39 0 | +0.62 0 |
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| 50 | 80 | +0.46 0 | +0.74 0 |
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| 80 | 120 | +0.54 0 | +0.87 0 |
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Limitation of Liability: The information contained in the tables mentioned-above is not an exhaustive statement of all relevant information. It is a general guide for customers to the products and services available from Dhand Steels and no representation is made or warranty given in relation to this information or the products or processes it describes.
