The forging industry is the pillar industry of modern industrial production. Many complex and mechanically demanding parts are preferred to be produced by means of forging and blanking. Compared with the cast parts, the forged parts are fine in structure, reasonable in carbide distribution and streamline distribution, and have been inferior in hardness, plasticity, toughness, etc., and have the most superior comprehensive mechanical properties. In addition, replacement can also save after forging a metal material, reducing the amount of machining shavings, improve productivity.
Forged workpieces, generally used as blanks for mechanical parts, are used to eliminate the forging stress and facilitate subsequent cutting. After forging, appropriate heat treatment is performed, and final heat treatment is performed after machining. Mechanical properties are the most important performance indicators for forged parts. Tensile testing is required for almost all forged parts, and most forged parts require a Brinell hardness test. The workpiece after mechanical processing and final heat treatment shall be subjected to Rockwell hardness test. If the workpiece size is too large, the Rockwell hardness test cannot be performed, and the Shore or Leeb hardness test may be used instead.
The authors collected and stipulated some of the requirements for the hardness requirements of forged parts in the American standard ASTM.
This article has two main parts. The first part lists the requirements for hardness requirements of typical forged products in American Standard ASTM. The second part introduces the selection method of hardness tester for forged products.
Provisions on the hardness of forged parts in the American ASTM standard
1. Carbon steel forgings used as pressure vessel components (ASTM A266/A266M-90)
Suitable for 4 grade carbon steel forgings for boilers, pressure vessels and related equipment. The Brinell hardness can be checked at any position on the forged part. The hardness value should be within the following range:
Grade Brinell hardness allowable range (HB)
1 121-170
2 and 4 137-197
3 159-207
2. Alloy forged steel rolls for cold rolling and hot rolling (ASTM A427-87)
A homogeneous hardened alloy forged steel roll for cold rolling and hot rolling of flat rolled black or non-ferrous metals. Hardness requirements.
The manufacturer shall provide the rolls in accordance with the hardness range agreed by both the supplier and the buyer.
The hardness test shall check the hardness of each roll, and the hardness value shall be within the scope specified in the contract. It can be tested using a Shore hardness tester, a Rockwell hardness tester or a Vickers hardness tester. The hardness test procedure, the number of tests and the location can be agreed upon by the supplier and the buyer. In order to ensure the uniformity of the longitudinal and transverse directions of the rolls, a sufficient number of hardness tests should be carried out for each roll. The manufacturer shall provide a hardness test report, and the model number of the steel number, roll, model and hardness tester shall be written in the report.
3. General industrial carbon steel and alloy steel forged parts (ASTM A668-90)
Suitable for general industrial carbon steel and alloy steel forgings for non-treated and heat treated.
Tensile test: Forged parts should meet the tensile properties shown in the table below.
Hardness test: Brinell hardness test shall be carried out after final heat treatment (except for Class A forgings) and roughing; each forged part with weight equal to or less than 7000 lbs (3180 kg) shall be subjected to Brinell hardness test.
The average hardness reading on each forged part shall be within the range specified in the table below. The tolerance of hardness of any forged piece weighing more than 250 lbs (113 kg) shall not exceed 30HB for Class A to Class E, 40HB for Class F to Class J, and 50HB for Class K to Class N.
Two hardness tests shall be carried out on each of the discs, rings and hollow forged parts weighing more than 250 pounds (113 kg). The locations of these two tests should be in the middle of the radius and should be 180 degrees apart. For example: 3:00 and 9:00 clock positions on one side and clock positions at 6:00 and 12:00 on the opposite side. For solid forged parts weighing more than 250 lbs (113 kg), the hardness test shall be carried out at least 4 times on the periphery of the forged part, 2 times at each end, 180 degrees apart. For forged parts with a weight of 250 lbs or less (113 kg), the Brinell hardness test shall be carried out on the fractured specimens representing a furnace steel or several furnace steels contained in each heat treatment furnace batch. It should be within the hardness range specified in the table below.
Forged parts can only be supplied according to the hardness test if required by the purchaser. Mechanical performance requirements
4. Stainless steel and heat-resistant steel forgings (ASTM A473-91a)
Austenitic suitable for general purpose use and low or high temperatures, austenitic - ferritic, ferritic and martensitic stainless steel forging and heat.
Mechanical performance requirements
Materials should meet the room temperature mechanical strength requirements specified in the table below.
For ferritic and martensitic steels, the manufacturer may specify that the tensile test be replaced by the hardness requirements in accordance with the following table.
Martensitic grade forgings shall be capable of meeting the hardness requirements specified in the table below after heat treatment.
Mechanical performance requirements
Heat treatment and hardness requirements
5. Carbon steel and alloy steel forgings for reducer size gears (ASTM A291-90)
Suitable for normalized and tempered carbon steel forged parts and quenched and tempered alloy steel forged parts for large and small gears.
Brinell hardness requirement
The hardness of the forged parts shall comply with the requirements specified in the following table. The Brinell hardness test shall be carried out on the parts prepared on the forged parts after machining to the size of the purchaser and the stress relief.
The number and location of hardness tests. For each forged part with a diameter greater than or equal to 8 inches (203 mm), four Brinell hardness tests shall be performed on the outer surface of the portion where the teeth are cut out, that is, two on each spiral line separated by a 180o angle. test.
Mechanical performance requirements
6. Carbon steel forgings used as pipe members (ASTM A105/A105M-87a
Carbon steel forged pipe components for pressure systems operating at room temperature and high temperatures, including flanges, pipe fittings, valves and similar components. The maximum weight of forged parts manufactured in accordance with this standard is limited to 10,000 pounds (4540 kg).
Stretching test
If the forged parts are too small, they can be accepted only according to the hardness test. Each batch of forged parts should be arbitrarily taken one hundredth or tenth forged parts (small value), and prepared according to the Brinell hardness test method in ASTM A370 standard. As such, and testing, the location of the indentation should be selected by the manufacturer, but should be chosen to represent the location of the entire forged part. A forged part should have an indentation, but several additional indentations can be additionally pressed to determine a representative hardness value. The hardness of all forged parts should be between HB137-187.
Hardness test
For each continuous or batch workpiece, a minimum of 2 forged parts shall be used for the hardness test to ensure that the hardness of the forged parts is within the range specified in the table below. The test shall be carried out in accordance with ASTM A370, and the hardness shall be measured at any position of the forged part to verify compliance, but such test shall not affect the use of the forged part.
The purchaser may test the hardness of any of the forged parts on the forged part at any position, and the hardness value shall be between HB137-187. Any forged parts that are not within the specified hardness range shall be rejected.
Mechanical performance requirements
7. Forged or rolled alloy steel pipe flanges and forged pipe fittings, valves and components for high temperature operation pipes (ASTM A182/A182M-91)
Suitable for pipe fittings for low pressure alloy steel and stainless steel for pressure systems, including flanges, valves and similar components.
Hardness test
Forged parts treated by batch or continuous heat treatment furnace according to the regulations, at least two samples shall be taken in each batch, and the hardness test shall be carried out in accordance with ASTM A370 to ensure the hardness of the forged parts in the hardness range of each grade specified in the following table. Inside. The buyer can test any part of the forged part to verify compliance, but such testing must not result in the forging being unusable.
When the number of tensile tests can be reduced when certain regulations are met, additional hardness tests should be performed on the specified forged parts or on the samples, and dispersed throughout the batch of forged parts. Forged parts processed by batch heat treatment furnace, at least 8 samples per batch, forged parts heat treated by continuous furnace, at least one sample per hour, such as less than 8 batch forged parts of batch furnace, each All forged parts should be tested. If any one of the tests exceeds the specified hardness range, the entire batch of forged parts should be reworked.
Heat treatment is carried out, and ferritic and martensitic grade steels (each furnace steel shall be subjected to a tensile test in each heat treatment furnace batch).
When required by the purchaser, each forged part shall be subjected to a hardness test, and the hardness value shall comply with the following table.
8. Alloy steel forgings for carburizing (ASTM A837-90)
Alloy steel forged parts for carburizing applications.
Hardness requirement
The maximum hardness value of the forged part is 229HB.
The hardness test shall be carried out on the forged parts preparation table after machining according to the requirements of the purchaser.
For forged parts that are not geared, the number and location of the hardness test can be agreed between the supplier and the buyer.
For forged parts of gears with a diameter greater than or equal to 8 inches (205 mm), four Brinell hardness tests shall be performed on the outer surface of the incisor, ie two tests shall be performed on each spiral at an angle of 180o. And the tests done on these two spirals should be separated by a 90o angle.
For forged parts less than 8 inches in diameter, two Brinell hardness tests are to be performed, one for each spiral on a 180° angle. For hollow cylindrical forged parts, a hardness test is performed at each end 180° apart. The hardness test shall be carried out at a width of 1/4 of the diameter of the tooth.
Test method for hardness of forged parts
In order to eliminate the processing stress, adjust the structure, refine the grain, and prepare good conditions for the subsequent cutting process, the forged part is subjected to appropriate heat treatment after processing, including annealing, normalizing, normalizing and tempering, quenching And tempering, etc. In order to ensure the heat treatment effect, the hardness value of the workpiece is mostly specified within a certain hardness range, and a few are specified below a certain hardness value. Most of the hardness test methods use Brinell hardness testers, and a few use Rockwell hardness testers.
Large workpieces can be either Shore hardness or Leeb hardness testers.
As we all know, the hardness test of forged parts mainly adopts Brinell hardness tester. The Brinell hardness value is almost required in the standard or the user's drawings. Various types of forged parts are required to be tested one by one, and each workpiece is also required. Detect multiple points.
For small forged parts, it can be tested directly on a benchtop Brinell hardness tester. Large and medium-sized forged parts cannot be tested on desktop machines. There are two types of hardness testing methods. One is to use a portable Brinell hardness tester, and the other is to use other portable hardness testers, which are then converted into Brinell hardness values ​​after measurement.
Forged parts are generally only blanks of mechanical parts. After the forged parts are produced, they are sent to a mechanical processing factory for cutting, and the final heat treatment is performed after the cutting. The final heat treatment methods include normalizing, quenching-tempering, carburizing, nitriding, local high frequency quenching, and the like. Some of the final heat-treated workpieces can be used directly as mechanical parts, some of which are finalized by grinding and then used as mechanical parts.
The mechanical parts processed from the forged blanks have the best final mechanical properties compared to the mechanical parts processed by other methods (such as extrusion, rolling, casting, etc.). These workpieces must have good toughness and meet the specified hardness. They must have the strength, wear resistance, surface hardness or local hardness of the workpiece under the conditions of use. Therefore, the final heat-treated workpiece is subjected to accurate hardness testing, and the hardness tester used should be a Rockwell hardness tester. A benchtop Rockwell hardness tester can be used when the workpiece is small. The workpiece is large, and a portable Rockwell hardness tester should be used when it is heavy or long. When there is no portable Rockwell hardness tester or the hardness test accuracy is not high, a Shore hardness tester, a Leeb hardness tester or a hammer type Brinell hardness tester can be used.
At present, there are mainly mature portable Brinell hardness testers at home and abroad:
1. Hydraulic portable Brinell hardness tester
This instrument uses the hydraulic principle and relies on manual pressurization to produce 3000 kg of test force. The instrument has a pressure relief valve. When the pressure reaches 3000kg, the pressure relief valve is opened and the pressure will fall. The instrument specification stipulates that it should be pressurized three times, so that the pressure gauge pointer hits 3000kg three times instead of Brinell. In the hardness test method, the 3000 kg force is applied for 15 seconds. This test method is specified in American Standard ASTM E110.
The effect of the above three pressurization method is the same as the 3000kg force specified in the standard, and the effect produced by pressurizing for 15 seconds is not exactly the same, and the speed of the afterburning is different, and the effect will be different. Therefore, the accuracy of this instrument is lower than that of the desktop. Despite this, the instrument has been widely used, and its test accuracy has been able to meet the requirements for forged parts.
This kind of instrument is not currently produced in China. The typical foreign instruments are KING type produced by American company, 134 type produced by British Fushun Company and WHB120 type produced by American Wobate Company.
2, the cutting type portable Brinell hardness tester
The instrument uses a handle to drive a precision screw system to apply the test force, and uses a shear pin to precisely control the test force. The instrument uses a test force of 1580 kg. When the test force reaches 1580 kg, the shear pin is broken and the test force is unloaded. except. When the test force reaches 1580 kg, the shear pin is broken, and the test force disappears instantaneously. It is impossible to maintain the standard 15 seconds. In order to compensate for this difference, the instrument manufacturer has carried out a large number of comparative tests according to the formula in the Brinell hardness test principle, established a mathematical model, and made a Brinell hardness table. According to the diameter of the indentation after the test, the corresponding table can be obtained. Brinell hardness value. The instrument head diameter is Φ7.26mm, and the test condition is F/D2=30, which is equivalent to the test condition of 3000kg force and 10mm ball. The instrument test force error is less than 1%, and the Brinell hardness test accuracy is 2-3%.
This kind of instrument has been produced in China. The PHB150 and PHB300 models produced by Shenyang Tianxing Testing Instrument Co., Ltd. are instruments of this principle. This type of instrument produced abroad is a STE type produced by ERNST, Switzerland.
3, hammer type Brinell hardness tester
The hammer type Brinell hardness tester relies on hammering to simultaneously press the steel ball into the surface of the sample and the standard hardness block, and compares the diameter of the sample indentation with the diameter of the standard hardness block indentation to determine the Brinell hardness value of the sample. This is a simple dynamic hardness tester. The hardness tester can determine the hardness of the forged part approximately and quickly. The instrument has a simple structure and is convenient to use, and the error is generally greater than 10%.
4, portable simple Brinell hardness tester
This is a simple dynamic hardness tester. The instrument uses a spring to apply an impact force to the steel ball, so that it is pressed into the surface of the sample to obtain an indentation. After measuring the diameter of the indentation, the Brinell hardness value is obtained by looking up the table, and the error of the instrument is also greater than 10%.
5, shear-type hammering Brinell hardness tester
The shear-type portable Brinell hardness tester can be conveniently taken down as a hammer-type Brinell hardness tester. The test force can be accurately controlled by the shear pin, and the test accuracy can reach ±5%, and its accuracy is significantly higher than other Hammer Brinell hardness tester, this instrument can be tested by touching one side of the workpiece, and can test any large workpiece. It is very suitable for one-piece inspection of general forged parts at the production site, and only one test is required for each test. A cheap cut-off can be used.
When the forged parts are large, inconvenient to move, and inseparable, they cannot be tested on a benchtop Brinell hardness tester, and portable Shore hardness and Leeb hardness testers are often used.
6, Shore hardness tester
The Shore hardness tester uses the principle of dynamic hardness test to let a steel ball fall from a certain height and impact on the surface of the sample. Under the action of this impact, the surface of the sample is plastically deformed, and part of the energy is absorbed. The remaining energy makes the steel The ball bounces back. The harder the sample, the smaller the deformation and the higher the bounce height. The maximum hardness of the steel ball rebound is tested to obtain the hardness of the sample.
The Shore hardness tester is a portable instrument that can test a variety of large workpieces. However, this type of instrument requires vertical use. It requires a high surface finish of the workpiece, which affects the accuracy of the test. The error is also large. The accuracy should be on the desktop. Between the old hammered Brinell hardness tester. The Shore hardness test is generally used for the hardness test of forged steel rolls.
7, Leeb hardness tester
The Leeb hardness tester is an instrument developed in the last decade. It is an improvement of the Shore hardness tester. It also uses a steel ball to impact the surface of the sample. It measures the ratio of the rebound speed and the falling speed of the steel ball at 1 mm from the surface of the sample. The instrument is electronic, with a computer that does not have to be used vertically, and the test value can be automatically converted to Brinell, Rockwell or Shore hardness values. The instrument is compact and easy to use. It can test different parts of the workpiece. The test accuracy is higher than the Shore hardness tester, which is much lower than the Brinell and Rockwell hardness tester.
The Leeb hardness tester also requires a high surface finish of the workpiece, which affects the accuracy of the test. The error in conversion to Brinell hardness is also large. Despite this, due to its simple operation and ease of use, it has been quickly accepted by people, and it has been widely used in forging parts, especially for workpiece hardness testing after finishing.
Large workpieces are generally inconvenient to move, and do not allow cutting, but the hardness detection accuracy requirements are higher. In the past, portable Rockwell hardness testers for large workpieces that lack high precision have been used worldwide. As a last resort, people had to use a lower precision Shore hardness tester. Later, the Shore hardness tester was modified to produce a Leeb hardness tester, and the main disadvantage of the Leeb hardness tester was its low precision, especially when the surface of the workpiece was not smooth. Accurate hardness testing of large workpieces has always been a problem that plagues people.
However, the situation is different now.
8, large portable Rockwell hardness tester
In 2008, Shenyang Tianxing Test Instrument Co., Ltd. produced a large portable Rockwell hardness tester of PHR series. The opening dimensions of the instrument are 200mm×100mm, 200mm×250mm, 500mm×300mm (width×depth). The accuracy of the instrument is the same as that of the desktop 150A. It can meet the requirements of the national standard GB/T 230. After testing by the Chinese Metrology Institute, the instrument error is less than 1.5HRC and the minimum can reach 1.0HRC. It can test various large workpieces made from forged blanks after final heat treatment. It can test plates, blocks, tubes, shafts and other shapes. The shape of the instrument is like a large micrometer, as long as the instrument can be firmly installed. On the workpiece, and the probe can be perpendicular to the surface of the workpiece, in principle any workpiece can be tested.
9, chain portable Rockwell hardness tester
In 2008, Shenyang Tianxing Testing Instrument Co., Ltd. also produced the PHR series chain Rockwell hardness tester, which is specially used to test large workpieces with cylindrical surfaces or other curved surfaces such as shafts, tubes and rings. The test range of the instrument is divided according to the diameter of the workpiece: 200-450mm, 400-850mm, 800-1600mm. Workpieces with a diameter of up to 1600 mm can be tested, and in principle, larger sizes can be manufactured if required. This instrument uses the same measuring head as the PHR C portable Rockwell hardness tester and has the same test accuracy. It has been tested by China Metrology Institute with an error of less than 1.5HRC.
10, portable Bloor hardness tester
In 2008, Shenyang Tianxing Testing Instrument Co., Ltd. also developed the PHBR series portable Bloor hardness tester, which adds the function of Brinell hardness tester to the PHR series Rockwell hardness tester, which has two hardness test functions. The instrument is available in three sizes: small, large and chain. The instrument meets the standards of Brinell and Rockwell hardness tests at home and abroad, and the test accuracy is high. The test value meets the product standard or drawing requirements of most metal parts without conversion, and can solve most metal hardness tests encountered in the industrial field. problem. The instrument is ideal for testing the hardness of castings .
Several portable hardness testers produced by Shenyang Tianxing provide a very important means of testing for the foundry industry, enabling accurate hardness testing of large cast blanks and finished parts. The test principle of the instrument complies with the specifications of most casting products. Measurement results are also easily accepted in domestic and foreign trade. The adoption of these instruments will certainly contribute to the quality improvement of China's foundry products and the technological advancement of the foundry industry.
The successful manufacture of PHBR large Bulu hardness tester and chain type Blo hardness tester provides a much-needed detection method for accurate hardness detection of large workpieces. The application of this instrument will improve the product quality and process level of large workpieces, and will promote heavy duty. Technological advances in the fields of machinery and large workpiece production.
Aluminum Profiles are more and more used in the production of doors and windows being their advantages such as light weight, high strength, corrosion resistance, and high cost performance. In addition, aluminum windows and doors have various styles and easy to install. It is an excellent choice for doors and windows of modern buildings.
Aluminum Extrusion Manufacturers In Usa,Aluminum Extrusion Usa,Aluminium Extrusion Usa,2080 Aluminum
Foshan Knilex Aluminum Co., Ltd. , https://www.aluprofilemaker.com