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Bearing Steel 100Cr6-Through-hardening Bearing Steel

Chemical composition

Through-hardening steel contains typically 1% carbon and alloying elements for hardenability, exhibiting very high strength but low ductility. Used with martensitic or bainitic hardening.

100Cr6 is equivalent to AISI 52100, GB GCr15.

Heat Treatment

In order to harden steel, the iron matrix must contain a certain amount of carbon.

The higher carbon content in the steel the higher achievable hardness. In through-hardening steel, there is a relatively high level of carbon added to the steel. When the component is heat treated, it becomes hard all the way through from the surface to the core, hence the term “through-hardened”. Through-hardened steel components are relatively brittle and can fracture under impact or shock loads.

Applications

for through-hardening bearing steel are typically roller bearing components but also components that require high fatigue strength such as diesel injection components.

The hardness levels these steel reach also makes them excellent in wear applications or cutting/slitting/grinding applications.

When also combined with a stabilizing heat treatment they give a dimensional stability needed in many tool steel applications.

What is Engineering Steel?-30crnimo8-Alloy Steel

30crnimo8 round bar stock

1.Grade 30CrNiMo8 is used for production of heavily loaded parts, shafts and drive axes, steering shafts, crankshafts of engines, screws and elements exposed to temperatures in the power industry.

2. 30CrNiMo8 equal to 1.6580, 30NCD8, 30CND8 alloy steel

3. Alloyed structural steel with medium hardenability designed for heavy duty components, characterized by high elasticity and strength properties reaching over 1560 N/mm2 at small diameters. When softened, the hardness reaches max. 248 HRB.

4 development direction of special steel bearing steel

Bearings are widely used in mining machinery, precision machine tools, metallurgical equipment, heavy equipment and high-end cars and other major equipment fields, as well as wind power generation, high-speed rail motor cars and aerospace and other emerging industries. The bearings produced in China are mainly medium and low-end bearings and small and medium-sized bearings, which are characterized by low-end surplus and high-end lack. Compared with foreign countries, there is a big gap in high-end bearings and large bearings. China’s high-speed railway passenger car special supporting wheelset bearings all need to be imported from abroad. For the key bearings used in aerospace, high-speed railway, high-end cars and other industrial fields, there is a big gap between China’s bearings and the advanced level in service life, reliability, DN value and bearing capacity. For example, the service life of foreign automobile gearbox bearings is the lowest of 500000 km, while the service life of domestic similar bearings is about 100000 km, with poor reliability and stability.
Aviation
As a key basic component of aero-engine, the second generation aero-engine bearing with thrust ratio of 15-20 is being developed abroad, which is ready to be assembled into the fifth generation fighter around 2020. In the past 10 years, the United States has developed the second generation of bearing steel for aero-engine, and the representative steels are css-42l with high strength and corrosion resistance at 500 ℃ and x30 (cronidur30) with high nitrogen and rust resistance at 350 ℃. China is developing the second generation of bearing steel for aero-engine.
Automobile
For automotive hub bearings, the first and second generation of hub bearings (ball bearings) are widely used in China, while the third generation of hub bearings have been widely used in Europe. The main advantages of the third generation hub bearings are reliability, short payload spacing, easy installation, no adjustment, compact structure, etc. At present, most of the imported vehicles in China adopt this kind of lightweight and integrated hub bearing.
Railway vehicles
At present, China’s railway heavy haul train bearings are made of domestic ESR g20crni2moa carburized steel, while foreign countries have applied the vacuum degassing smelting technology, inclusion homogenization technology (IQ steel), ultra long life Steel Technology (TF steel), fine heat treatment technology, high purity bearing steel (EP steel) and other technologies Surface super hardening treatment technology and advanced sealing lubrication technology are applied to the production and manufacturing of bearings, which greatly improves the service life and reliability of bearings. The quality of ESR bearing steel in China is not only low, but also the cost is 2000-3000 yuan / ton higher than that of vacuum degassing steel. In the future, China needs to develop ultra-high purity, fine-grained, homogenized and stable quality vacuum degassing bearing steel to replace the current ESR bearing steel.
Wind power and energy
For wind turbine bearings, at present, China has not been able to produce high-tech spindle bearings and speed increaser bearings, basically relying on imports, and the localization of bearings for wind turbine units above 3MW has not been solved. In order to improve the strength, toughness and service life of wind turbine bearings abroad, a new type of special heat treatment steel SHX (40crsimo) is used. For yaw and variable pitch bearings, the depth of hardened layer, surface hardness, width of soft belt and surface crack are controlled by surface induction hardening heat treatment; Carbonitriding is used for speed increaser bearing and main shaft bearing, so that more stable volume fraction of retained austenite (30% – 35%) and a large number of fine carbides and carbonitrides can be obtained on the surface of parts, and the service life of bearing under pollution lubrication condition is improved.
In order to improve the service life and operation accuracy of rolling mill bearings, it is necessary to research and develop ultra-high purity vacuum degassing smelting of GCr15SiMn and g20cr2ni4 bearing steels for rolling mill and large austenite mass control heat treatment of bearing surface in the future. NSK and NTN have developed the surface austenite strengthening technology respectively, that is, TF bearing and WTF bearing have been developed by increasing the surface austenite content, so that the service life of bearing has been increased by 6-10 times.

The future R & D direction of bearing steel in China is mainly reflected in four aspects:
One is economic cleanliness: on the premise of considering economy, further improve the cleanliness of the steel, reduce the content of oxygen and titanium in the steel, so that the mass fraction of oxygen and titanium in the bearing steel is less than 6 × 10-6 and 15 × The content and size of inclusions in the steel are reduced and the distribution uniformity is improved.
The second is the refinement and homogenization of microstructure: through the application of alloying design and controlled rolling and cooling process, the uniformity of inclusions and carbides can be further improved, the network and band carbides can be reduced and eliminated, the average size and maximum particle size can be reduced, and the average size of carbides can be less than 1 μ The goal of M; The grain size of the matrix is further improved, and the grain size of the bearing steel is further refined.
The third is to reduce macrostructure defects: further reduce the central porosity, central shrinkage and central composition segregation in bearing steel, and improve the uniformity of macrostructure.
Fourth, high toughness of bearing steel: through new alloying, hot rolling process optimization and heat treatment process research, improve the toughness of bearing steel.

heat treatment of H13 die steel

1. Soft spots on the surface of the mold
There are soft spots on the surface of H13 tool/die steel after heat treatment, which will affect the wear resistance of the too/diel and reduce the service life of the die.
(1) Causes
1) There are oxide scale, rust spot and local decarburization on the surface of the mould before heat treatment.
2) After the mold is quenched and heated, the selection of cooling and quenching medium is improper, and the impurities in the quenching medium are too much or aging.
(2) Preventive measures
1) The oxide scale and rust should be removed before the heat treatment of the mould. The surface of the mould should be properly protected during quenching and heating. The mould should be heated in vacuum electric furnace, salt bath furnace and protective atmosphere furnace as far as possible.
2) When the mold is cooled after quenching and heating, the appropriate cooling medium should be selected, and the cooling medium used for a long time should be filtered or replaced regularly.
2. Poor organization of die before heat treatment
The final spheroidizing structure of the die is coarse and uneven, the spheroidizing is not perfect, and there are network, band and chain carbides in the structure, which will make the die easy to produce cracks after quenching and cause the die to be scrapped.
(1) Causes
1) There is serious carbide segregation in the original structure of die steel.
2) Poor forging process, such as too high forging heating temperature, small deformation, high stop forging temperature, slow cooling rate after forging, makes the forging structure coarse and has network, band and chain carbide, which is difficult to eliminate during spheroidizing annealing.
3) Poor spheroidizing annealing process, such as too high or too low annealing temperature and short isothermal annealing time, can cause uneven microstructure or poor spheroidizing.
(2) Preventive measures
1) Generally, H13 die steel with good quality should be selected according to the working conditions of the die, the production batch and the strength and toughness of the material itself.
2) In order to eliminate the inhomogeneity of network and chain carbides and carbides in raw materials, the forging process is improved or normalizing heat treatment is adopted.
3) Solution refining heat treatment can be used for high carbon die steel with severe carbide segregation which can not be forged.
4) To make correct spheroidizing annealing process specification for forged die blank, quenching and tempering heat treatment and rapid uniform spheroidizing annealing can be used.
5) Reasonable charging can ensure the temperature uniformity of mould billet in the furnace.
3. Quenching crack of mould
The crack of H13 die steel after quenching is the biggest defect in the process of die heat treatment, which will scrap the processed die and cause great loss in production and economy.
(1) Causes
1) There is serious network carbide segregation in H13 die steel.
2) There are mechanical or cold plastic deformation stresses in the die.
3) Improper operation of mold heat treatment (too fast heating or cooling, improper selection of quenching medium, too low cooling temperature, too long cooling time, etc.).
4) The complex shape, uneven thickness, sharp angle and threaded hole of the die result in excessive thermal stress and microstructure stress.
5) Overheating or overburning occurs when the heating temperature of die quenching is too high.
6) Tempering is not timely or holding time is not enough after quenching.
7) When the die is repaired and quenched, it is reheated and quenched again without intermediate annealing.
8) The heat treatment of the mould is poor and the grinding process is improper.
9) There are high tensile stress and microcracks in the hardened layer during EDM after heat treatment.
(2) Preventive measures
1) Strictly control the internal quality of raw materials for die steel
2) The forging and spheroidizing annealing processes were improved to eliminate network, band and chain carbides and improve the uniformity of spheroidizing structure
3) The die after machining or cold plastic deformation should be annealed (> 600 ℃) and then quenched.
4) For the mould with complex shape, asbestos should be used to plug the threaded hole, wrap the dangerous section and thin wall, and adopt the step quenching or isothermal quenching.
5) Annealing or high temperature tempering is required when repairing or renovating the mould.
6) The mould should be preheated during quenching and heating, precooling measures should be taken during cooling, and suitable quenching medium should be selected.
7) The heating temperature and time of quenching should be strictly controlled to prevent the die from overheating and overburning.
8) After quenching, the die should be tempered in time, the holding time should be sufficient, and the high alloy complex die should be tempered 2-3 times.
9) Choose the right grinding process and grinding wheel.
10) The die EDM process was improved and stress relief tempering was carried out.
4. The structure of the die is coarse after quenching
After quenching, the structure of the die is coarse, which will seriously affect the mechanical properties of the die. When the die is used, it will fracture and seriously affect the service life of the die.
(1) Causes
1) The actual quenching temperature of die steel is far lower than that of required die material (for example, GCr15 steel is regarded as 3Cr2W8V steel).
2) The correct spheroidizing process was not carried out before quenching of die steel, resulting in poor spheroidizing structure.
3) The heating temperature of die quenching is too high or the holding time is too long.
4) If the mould is not placed properly in the furnace, it is easy to overheat in the area near the electrode or heating element.
5) For the die with large cross-section variation, improper selection of quenching and heating process parameters leads to overheating at thin cross-section and sharp corner.
(2) Preventive measures
1) The steel products should be inspected strictly before they are put into storage to prevent them from being mixed up.
2) Correct forging and spheroidizing annealing should be carried out before quenching to ensure good spheroidizing structure.
3) The quenching and heating process specification should be established correctly, and the quenching and heating temperature and holding time should be strictly controlled.
4) Check and calibrate the temperature measuring instrument regularly to ensure the normal operation of the instrument.
5) When the mould is heated in the furnace, it should keep a proper distance from the electrode or heating element.

Metal(Steel) machining

Metal manufacturing involves many processes, one of which is processing, which is a necessary requirement of modern large-scale manufacturing. The machine cuts, drills, grinds or otherwise shapes the metal by removing some of the metal using a cutting or grinding surface. Generally, the machine tool has two parts: one part holds and guides the metal to be formed, and the other part completes the forming work. Machining, especially in the computer age, can carry out accurate and fine metal processing.

Casting, forging and machining
There are several main forms of creating metal shapes.
Casting is the process of filling a mold with molten alloy and cooling it. Forging metal can change the properties of materials by applying compressive force to change the metal lattice. Bending, twisting, impact and folding operations are common in forging. To machine, carve, grind, cut, drill, or otherwise mold metal. The way a mechanic handles metal is similar to the way a carpenter handles wood; Although the shape and finish have been processed, most of the materials have not changed.
In modern times, machining is usually the finishing step of forging or casting products, in order to make the forging or casting objects reach the precision tolerance range. Milled plates, blanks and bars can also be machined from their original geometry.
Casting and forging usually occur before machining. The processed object may be further processed before the metal object is finished. Workpieces can be connected by fasteners or welds, heat treated, or other surface treatment.

What is CNC machining? Machining tool steel
CNC stands for computer numerical control. In CNC machine, the computer precisely controls the movement of the machine. The design generated in CAD software is converted to motion on X, y and Z axes. In this way, a computerized machining shop can carve metal in three dimensions with precise tolerances.

Commonly used machine tools are as below:
Lathe – turning the metal work against the cutting tool,

Drilling machine – pushing the drill through the metal surface

Grinder – turning the abrasive or grinder against the metal work,

Belt machine – cutting the metal work with a continuous saw blade,

Milling machine – shaping the metal work on the surface with a rotary cutting tool,

Broaching machine – filing objects, only remove a small amount of material

Laser cutting and etching – beams used to cut, drill or etch objects

Ultrasonic machining – Ultrasonic and abrasive slurries to remove metal

Electron beam machining – a beam of electrons generates high heat and vaporizes metal

Chemical and electrochemical methods – use chemicals to remove and shape metal

Lathe is the ancestor of many machine tools. The lathe rotates the object against the edge of the cutting tool. Therefore, the lathe can be used for boring, drilling, thread cutting, milling and grinding: as long as it can turn metal products, the lathe can replace other tools.

The tool steel can be devided into the below:

Rough machining H13 tool steel.
Tool steel turning guidelines include tools and parts manufacturing applications.
Metal cutting should be considered as an integrated system, which includes three equally important elements: work pieces, tools and machines. Traditionally, end users are more focused on cutting tools than on the machine tools (assuming it has enough power to do the work), unfortunately, too little attention is paid to the work pieces. The information of workpiece is usually limited to the type of work piece material, such as steel, cast iron, aluminum alloy, etc. The most important mechanical properties of the workpiece materials, such as hardness and ultimate tensile strength, are sometimes not provided or provided with customer requirements. If these data are missing, the integrated system of metal cutting will become incomplete. In this case, the maximum cutting productivity cannot be calculated.
Tool steel is high carbon steel, alloy steel and high speed steel which can be quenched and tempered. Traditionally, they are used to make tools for cutting, forming, and forming. Other applications include manufacturing parts that are critical to specific properties such as wear resistance, strength, toughness and hardness, which cannot be achieved by carbon steel, alloy or stainless steel.
The classification of tool steel is based on the system developed by the American Steel Association (AISI). The system classifies tool steel according to heat treatment, application or major alloy elements. There are six main categories and 10 subcategories, marked by letters followed by one or two digits.
In addition to AISI classification, tool steel is identified by the name in the unified numbering system for metals and alloys (UNS), which is established by the association of automotive engineers and the American Society for testing and materials. The UNs identification system consists of the letter T and five numbers: the first three identify the tool steel categories, and the latter two identify the grades of the tool steel categories.

Water hardening tool steel
The water hardening tool steel is basically carbon steel with 0.6% to 1.40% carbon. They are the cheapest tool steel.
Three types of water hardening steel of standard AISI (UNS) types are being produced: W1 (t72301), W2 (t72302) and W5 (t72305). W3, W4, W6 and W7 sections are no longer commonly used.
The water hardening tool steel has 100% processability grade, which is the basis for comparison with other tool steel groups. Compared with AISI 1212 steel, the cutting performance grade of water hardening steel is 40%.
The hardness of the steel is 150 to 200 Hb in annealed condition.
Water hardening steel is used for cutting tools (cutting blades, reamers, taps and twist drills), clamps and dies for blanking, stamping and thread processing.

Seismic tool steel
Seismic tool steel has been developed to provide an effective combination of high hardness, high strength and high toughness or impact fracture resistance. These steels were originally developed for springs and are still widely used in spring applications that require good fatigue resistance.
There are five types of seismic tool steel of standard AISI (UNS): S1 (t41901), S2 (t41902), S5 (t41905), S6 (t41906), and S7 (t41907). S3 and S4 are no longer used.
The main alloy element is silicon, which varies from 1.0% to 2.5%, depending on S-shaped steel. Silicon provides the ability of resisting softening during tempering to maintain the microstructure of fracture resistance.
Aisi S1 steel is the only grade containing tungsten (1.5% to 3.0%). This steel is also known as tungsten chisel steel, because it is used to make seismic tools.
The machinability of seismic tool steel is about 75%, while that of water hardening tool steel is 100%.
The hardness of annealed seismic tool steel is 175 to 225 Hb.
The application of these tool steels includes heavy blanking and forming dies, punches, chisels, shear blades, slitting knives, seals, heads, piercers and forming tools.

Cold working tool steel
Cold working tool steel does not have the alloy content required to resist high temperature softening. They are limited to the need to be at 400 ° To 500 ° F（200 ° To 260 ° C) Applications that have been heated for a long time or repeatedly in the range. The category is divided into three subcategories (Table 1).
The high hardness and wear resistance of oil hardening tool steel are derived from the high carbon content and medium content of chromium, molybdenum, vanadium, tungsten and silicon in the range of 0.85% to 1.55%.
There are four types of AISI (UNS) standards: O1 (t31501), O2 (t31502), O6 (t31506) and O7 (t31507).
The most popular oil hardening steel is O1. It has enough hardenability to produce enough hardening and surface hardness depth, thus prolonging service life. The toughness of O1 steel is slightly higher than other oil hardening steel, and it is the most widely used O-shaped steel. At 22 HRC, the tensile strength of O1 steel is 112 Ksi, while that of O2 steel is 108 Ksi. At 31 HRC, the tensile strength of O1 steel is 133 Ksi, while that of O7 steel is 128 Ksi. The minimum size change of O2 steel was observed during heat treatment. O6 steel contains free graphite in microstructure to improve the processability of complex die. O7 is the most wear-resistant Oil hardened steel, which may be the first choice for tool manufacturing and application.
O6 has a workability rating of 125%, which means that O6 steel is easier to process than water hardening tool steel. The machinability grades of other o-sections are about 65% to 90%.
The hardness of the tool steel is 200 to 250 Hb in annealed condition.
All oil hardening tool steels are used in similar applications, including blanking, forming, rolling, stamping, forming, cold trimming and drawing dies. The steel is also used to make reamers, taps, drills, small shear blades, slitting saws, round cutters and hobs, spindles, gauges, collets, broaches, polishing tools, knurled tools and punches.

Air hardened, medium hardening tool steel
Because of the combination of high carbon (0.55% to 2.85%) and other alloy elements with medium and high content (such as chromium, molybdenum, vanadium and nickel), air hardening steel can achieve its performance characteristics.
These steels are of eight standard AISI (UNS) types: A2 (t30102), A3 (t30103), A4 (t30104), A6 (30106), a7 (30107), a8 (30108), A9 (30109), and A10 (30110). A5 tool steel is no longer used.
The air hardening tool steel has high hardenability and high dimensional stability during heat treatment. They have good wear resistance, fatigue life, toughness and deep hardening properties.
Air hardening tool steel can be divided into chromium grades (types A2, A3, a7, a8 and A9) with 4.75 to 5.75% chromium and up to 1.0% manganese, and manganese grades (types A4, A6 and A10) with 1.60 to 2.50% and 0.90 to 2.20% manganese.
The chromium air hardening type is easier to obtain and widely used. Chromium type has higher wear resistance (at the same carbon content) and higher thermal hardness than manganese type. Compared with other A-shaped steel, A9 steel is the strongest, but also the worst wear resistance. However, the wear resistance of manganese type is poor and difficult to process.
The processability grade of medium alloy and air hardening steel is about 65%.
The hardness of the air hardening tool steel is 200 to 250 Hb in annealed condition.
The application of air hardening tool steel includes cold forming mould, blanking mold, bending mold, forming roll, drilling sleeve, knurled tool, assembly mould and measuring tool, and other applications requiring low heat treatment deformation and wear resistance.

High carbon and high chromium tool steel
High carbon and high chromium tool steel is the highest alloy content steel.
These steels have five standard AISI (UNS) types: D2 (t30402), D3 (t30403), D4 (t30404), D5 (t30405), and D7 (t30407). D1 and D6 are no longer used.
Each type contains 11 to 13% chromium as the main alloy element. All grades are characterized by high carbon content, ranging from 1.40% to 2.60%.
The machinability grade of high carbon and high chromium tool steel is 40% to 60%.
The hardness of high carbon and high chromium tool steel is 200-250hb under annealing condition.
The applications of these steels include spindle, hob, cold roll, Slitter, blanking die, forming die, press die, bushing, tap, broach, sand blasting nozzle, plug gauge and ring gauge.

Otai sells 42CrMo plate, H13, P20 and other special steel!

4140 Alloy steel plate

With over 20 years’pre-sales and after-sales special steel, Our steel materials meet DIN / ASTM / EN / JIS etc different international standards. For 4140 plate, we keep above 1000tons daily stock, which is the largest stockist in Sounth China.  We supply in Round bar, gauge plate steel, pipe, tube, rod, square, hexagonal, blanks, plate, sheet, precision ground flat bar.

4140 steel plate belongs to ultra-high strength steel, with high strength and toughness, good hardenability, no obvious temper brittleness, high fatigue limit and multiple impact resistance after quenching and tempering treatment, and good low temperature impact toughness. The 4140 flat bar is suitable for manufacturing large and medium-sized plastic moulds requiring certain strength and toughness.

Otai’s advantage:
1. There are thousands of tons of steel inventory in our warehouse, especially for 4140/42CrMo4 plate, Otai is the largest stockist in South China.
2. Small order can be received. Compared with large steel mills, MOQ is lower, which is more conducive to foreign small and medium stockers.
3. We can finish all kinds of machining process like milling, polishing, turning and other processing.
4. With independent testing equipment, including spectrometers, UT flaw detection equipment, etc., compared to traders, we can fully guarantee product quality for customers.

Customer case:

One of our customer in Vietnam purchased 1045 round steel to produce products from other suppliers, and the products cracked and collapsed during using. Due to the unstable life cycle of product parts, the customer’s production efficiency slows down, the production cost rises, and more importantly, the customer’s delivery commitment to the end user is badly affected.
In 2017, we received this customer’s question and went to Hanoi on a business trip to check the parts with quality problems. Our engineering proposed 4140 material as a substitute by checking the use environment of the parts and communicating the mechanical performance requirements with the customer’s product engineering, and introduce the advantages of 4140 in impact energy and tensile performance, Customer decided to replace 1045 with 4140. From that time, customers have been purchasing 4140 plate from us.

How to anneal spring steel

The purpose of spring steel annealing is to reduce the material stress, otherwise there will be barbed cracks during winding. During annealing, the material must be isolated from the air, otherwise surface decarburization will occur.
Annealing is a heat treatment process of heating spring steel to appropriate temperature, holding for a certain time, and then cooling slowly. Annealing is mainly used for casting, forging, welding blanks or semi-finished parts, for preparation of heat treatment. Pearlite structure was obtained after annealing.

The main purpose of annealing is to soften spring steel for cutting; Eliminate internal stress to prevent workpiece deformation; Refine the grain, improve the structure, prepare for the final heat treatment of parts. According to the composition and annealing purpose of spring steel, the common annealing methods are complete annealing, isothermal annealing, spheroidizing degradation, homogenizing annealing, stress relief annealing and recrystallization annealing.

1. Complete annealing and isothermal annealing
Complete annealing is to heat the spring steel to 30-50 ℃ for a certain period of time, cool it to below 600 ℃ with the furnace, and then air cool it out of the furnace. It is mainly used for casting and forging of hypoeutectoid spring steel, and sometimes for welding structure. The purpose of complete annealing is to refine grains, eliminate overheated fabric, reduce hardness and improve machinability. Complete annealing is not suitable for hypereutectoid spring steel in order to avoid secondary cementite precipitation along austenite grain boundary in network form, which will bring adverse effects on cutting and subsequent heat treatment. Complete annealing is time-consuming, and isothermal annealing is often used in production. The heating temperature of isothermal annealing is the same as that of complete annealing, but the cooling mode is different. Isothermal annealing is to cool rapidly to a certain temperature below, isothermal for a certain time to make austenite transform into pearlite structure, and then air cooling. For some alloy spring steels with stable austenite, the annealing cycle can be greatly shortened by isothermal annealing.

2. Spheroidizing annealing
Spheroidizing annealing is to heat the spring steel to 20-40 degrees, fully keep the temperature, and then cool it to below 600 degrees with the furnace for air cooling. When the spheroidizing annealing passes through AR1 temperature, the cooling should be slow enough to spheroidize eutectoid cementite. Spheroidizing annealing is mainly used for hypereutectoid spring steel. The purpose is to spheroidize the cementite in the spring steel, so as to reduce the hardness of the spring steel, improve the machinability, and prepare the structure for the later heat treatment process. If there is serious cementite network in the original structure of spring steel, normalizing should be carried out before spheroidizing annealing to ensure the effect of spheroidizing annealing.

3. Homogenization annealing (diffusion annealing)
Homogenization delayed ignition is to heat the spring steel to a temperature slightly lower than the solidus temperature (150-300 ℃), keep it for a long time (10h-15h), and then cool it with the furnace, so as to homogenize the chemical composition and microstructure of the spring steel. The energy consumption of homogenization annealing is high and the grain size is easy to coarsen. In order to refine the grain, complete annealing or normalizing should be carried out after homogenization annealing. This process is mainly used for alloy spring steel ingots, castings or forging billets with high quality requirements.

4. Stress relief annealing and recrystallization annealing
Stress relief annealing, also known as low temperature annealing, is to heat the spring steel to a certain temperature below AC1 (generally about 500-600 ℃) for a certain period of time, and then cool with the furnace. The purpose is to eliminate the residual stress of casting, forging, welding and cold stamping parts.
Recrystallization annealing is mainly used for spring steel after cold deformation, which can soften the hardening phenomenon caused by cold deformation.

How to select the right tool steel for your products?

The brand of tool steel and its application
Tool steels are available in various grades depending on their composition, the temperature range of forging or rolling and the type of hardening they experience. The general grades of AISI – SAE tool steel are O1, A2, and D2. These standard grades of steel are considered cold work steel, which can keep its cutting edge at up to about 400 °C. They have good hardness, wear resistance and deformation resistance.

Check our tool steel products page:https://otaialloysteel.com/products/tool-steel/
O1 is a kind of oil hardening steel with high hardness and good cutting processability. The grade of tool steel is mainly used for cutting tools, drill bits and knives and forks.
A2 is an air hardening steel containing an intermediate equivalent amount of alloy material (chromium). It has good machinability and wear resistance and toughness balance. A2 is the most commonly used air hardening steel variety, which is commonly used in punching and shaping punch, edge cutting mold and injection mold.
D2 steel can be Oil hardened or air hardened and contain a higher percentage of carbon and chromium than O1 and A2 steels. It has high wear resistance, good toughness and low deformation after heat treatment. The high carbon and chromium content in D2 steel makes it an ideal choice for the application that needs longer tool life.

Other tool steel grades include different types of alloys with a higher percentage, such as high speed steel M2, which can be selected for mass production. Various hot working steels can be up to 1000 ° C keep sharp cutting edge at higher temperature.

How can tool steel fail?
Before selecting tool steel grade, it is important to consider which tool is most likely to fail in this application by checking the failure tool. For example, some tools fail due to abrasive wear, in which the material being cut will wear the surface of the tool, although this type of failure occurs slowly and is predictable. Tools that wear to failure require tool steel with higher wear resistance.
Other types of faults are more catastrophic, such as cracking, fragmentation, or plastic deformation. For tools that have been broken or cracked, the toughness or impact resistance of tool steel should be increased (note that impact resistance will be reduced due to notch, undercut and sharp radius, which are common in tools and dies). For tools that deform under pressure, the hardness shall be increased.
But remember that the properties of tool steel are not directly related to each other, so for example, you may need to sacrifice toughness for higher wear resistance. That’s why it is so important to understand the characteristics of different tool steels and other factors (such as the geometry of the mold, the materials being processed, and the manufacturing history of the tool itself).

Tool steel cost
The last issue to consider when selecting tool steel grades is cost. If the tool is proven to be inferior and fails prematurely, the cut in in material selection may not reduce the overall production cost. Cost benefit analysis shall be carried out to ensure that the selected tool steel material can provide the required performance.

Why Pakistani customer turn to Otai Steel?

Otai accepts all kinds of large, medium and small orders, and can help customers with cutting, machining, and heat treatment to solve customers’ problems in one stop.

Otai’s advantage:
1. There are thousands of tons of steel inventory(https://otaialloysteel.com/products/ )in our warehouse, especially for 4140/42CrMo plate, Otai is the largest stockist in South China.
2. Small order can be received. Compared with large steel mills, MOQ is lower, which is more conducive to foreign small and medium stockers.
3. We can finish all kinds of machining process like milling, polishing, turning and other processing.
4. With independent testing equipment, including spectrometers, UT flaw detection equipment, etc., compared to traders, we can fully guarantee product quality for customers.

3 major traps in steel procurement:

• Using low-value materials as high-value materials; Otai will never be provide shoddy goods.
• Offering low prices to attract customers regardless of customer performance requirements; Otai will only quote the most accurate price based on customer needs.
• Delivery is not possible within the delivery period, making customers unable to keep up with the project; Otai promises to deliver within the fastest delivery time.

There are a Pakistani customer who had cooperated with us for many years, but in 2020 he didn’t place order, said that there was something wrong with our hardness. But he came back to us, place an order this year and paid the price the next day once we sent him the quotation. You know why? In fact, the customer recognized the quality of our products. Last year, he might have bought a bargain with an Indian supplier,  he now realizde that our products are reasonable in price and guaranteed in quality after stepping on a pit from other suppliers.

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What is the difference between 42CrMo and 42CrMo4?

42CrMo is a medium carbon alloy structural steel with good comprehensive properties and hardenability. It is often used in manufacturing gear, connecting rod, high strength bolts and other important parts in the processing process.
They come from different standards in different countries. 42CrMo is the material of Chinese standard GB / T 3077 and the specification of alloy structural steel. The material of 42CrMo4 belongs to EN 10083 series, Quenched and tempered steel.

1. Differences in chemical composition. As shown in the figure below, there is a slight difference in the content of element Si, and the content of Si in 42CrMo is less than that in 42CrMo4. In addition, according to gb3077, P and s contents can be divided into three grades, while 42CrMo4 only limits its maximum content.

2. Different Hardenability Requirements. The hardenability of 42CrMo has no specific value of quenching bandwidth. If there are special requirements, the buyer and the supplier can discuss the solution by themselves. The specific value of hardening bandwidth is specified in 42CrMo4. 42CrMo4 is divided into three grades h, HL and HH for reference when ordering.

3. Different delivery conditions. 42CrMo pipes are usually delivered in hot rolling and hot forging conditions. If the customer needs heat treatment conditions (annealing, normal goods, high temperature tempering), it should be indicated in the contract. For en1008342crmo4 pipe, there are five delivery conditions to choose from: no heat treatment, heat treatment, softening annealing, quenching and high temperature tempering.

4. Differences in impact test requirements. When the impact test is carried out according to GB / t2975, 42CrMo sample is taken at 1 / 4 of the outer diameter of the rod as the center of the rod with diameter greater than 50 mm. When the diameter of the sample bar is 25 mm, it should be modulated according to the requirements of heat treatment process, and then the tensile sample should be tested. In en10083 standard, bars are tempered according to the recommended heat treatment. When the sampling diameter is greater than 25 mm, the sampling position should be centered 12 mm around the outer diameter of the rod. In addition, 42CrMo uses Charpy u-notch toughness, while 42CrMo4 uses Charpy V-notch toughness. The two notches have the same depth, but the radii at the bottom of the notches are different (U-shaped 1 mm, V-shaped 0.25 mm).

Hot rolled carbon steel is a kind of metal alloy, which is mainly composed of iron and some carbon. These carbon will be rolled from the ingot to a certain size at a temperature higher than its recrystallization temperature. Forming hot rolled carbon steel at such a high temperature gives it excellent mechanical properties while keeping the cost lower than that of cold rolled carbon steel.

ASTM A36

ASTM A36 steel is one of the most popular hot rolled steels sold by steel mills. For hot rolled steel A36 is ASTM specified material. It is considered low carbon steel because its carbon content is usually 0.25% to 0.29% by weight. The “36” in A36 is important because it specifies a minimum yield tensile strength of 36000 psi. A36 has high machinability, weldability and excellent mechanical properties. This is one of the reasons why it is so popular, and part of the reason why it is widely used in structural applications.

C1010 and C1018
AISI C1010 and AISI C1018 are two very similar hot rolled steels. They are all low carbon. In fact, the only obvious difference between their chemical composition is their carbon content. C1010 is 0.08% to 0.13% by weight of carbon and C1018 is 0.14% to 0.20% by weight of carbon. Differences in carbon content between them may lead to slight changes in ductility and tensile strength, but in most cases they are very similar. Compared with alloy steel and high carbon steel, they are weldable, machinable and relatively easy to form. Tube C1010 and rod and mesh C1018. C1010 and C1018 are widely used in structural applications, as well as in automotive and furniture industries.

A1011
A1011 is another ASTM specified hot rolled steel plate. The grade can also have a small amount of other trace elements, making it a very flexible steel. It is widely used in steel structural applications, car body, drum, and general metal manufacturing.

C1026
C1026 is AISI specified steel, which closely imitates astm-a36 specified steel, as mentioned above. Their chemical properties overlap greatly, and their carbon content constitutes the upper limit of low carbon steel. Aisi 1026 has a target carbon content of 0.22% and 0.26% by weight. When they are all hot rolled, their mechanical properties are very similar. Both AISI c1026 and ASTM A36 are good choices when hot rolled strips are needed, with more strength in addition to a1011, C1010, C1018 or available. Several AISI hot-rolled steel parts are used in the field of automotive structures, such as c1026. C1026 is available in square and rectangular tubes.

A500
ASTM A500 is another low carbon hot rolled steel. It can pass its chemical composition in weight with up to 0.26% carbon and is quite similar to ASTM A36. The main difference between ASTM A500 and ASTM A36 is the shape available for each hot rolled steel. As mentioned earlier, A36 is available in round bar, rectangular bar, square bar, channel steel, angle steel, plate, pedal, round pipe, and shafting. A500, on the other hand, is used only for pipes, similar to other low carbon hot rolled steel plates for ASTM A500 applications; they are widely used in structural applications.

C1045
C1045 is another hot rolled steel designated by AISI. The difference between this hot rolled steel and the steel mentioned before is that it is medium carbon steel. When the carbon content is 0.42% to 0.50% by weight, it usually provides higher strength than low carbon hot rolled steel. C1045 also has enough carbon to be easily heat treated. This means that the mechanical properties can be changed by quenching, hardening and annealing. The use of c1045 is similar to that of low carbon hot rolled steel, but it is usually preferable to low carbon steel when strength is more concerned than ductility.

C1141
AISI c1141 is another medium carbon hot rolled steel, similar to c1045. However, AISI c1141 has different properties due to the addition of sulfur and manganese. First, heat treatment is more effective on c1141 than c1045. Secondly, c1141 is considered as a free working steel. This means that it’s easier on the machining tool, which is important as the carbon content increases, because the corresponding increase in hardness affects machinability. However, it is important to note that the addition of sulfur, which makes c1141 easy to process, also generally makes it non weldable. AISI c1141 is often used in parts that require a lot of machining and some types of fasteners.