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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.

ThyssenKrupp, Bohler and other top 500 brands are loyal customers of Otai for many years.

Directly click wechat and WhatsApp windows to respond immediately and solve the problem for you!

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.

3 steel grades suitable for making gear

Gear steel is the general name of steel used in gear manufacturing. Gear is one of the most widely used mechanical components, and is widely used in mechanical transmission. There are many types of gears, such as spur gear, chain gear, synchronous pulley, helical gear, internal gear, rack, straight bevel gear, arc bevel gear, zero bevel gear, staggered spiral gear, worm gear, etc.

Gear steel is a key material with high requirements for special alloy steel used in automobile, railway, ship and engineering machinery. Gear material needs strong bending fatigue strength and contact fatigue strength, and the tooth surface should have enough hardness and wear resistance, and the tooth core should have certain strength and toughness. Gears are usually made of forged steel, except for foundry plants with too large size (Dia > 400-600mm) or suitable for complex structures and shapes.
Carbon steel or alloy steel with carbon content of 0.15-0.6% is usually used in gear applications. The Microalloy Elements in gear steel can improve the toughness, impact resistance, wear resistance and adhesion of the material, and the mechanical properties of the material can also be improved by heat treatment or chemical heat treatment. Alloy gear steel usually does not include low carbon alloy steel, such as 15CrMo, 20Cr, etc. and medium carbon alloy steel: 40Cr, 42CrMo, 35CrMo, etc.

15CrMo
Carburizing surface quenching treatment is generally used to pay attention to the strength or toughness of parts or parts that need to bear a lot of friction, such as cylinder piston, spindle, gear, bolt, shaft, etc. It is used to make profile less than 30mm under high speed, medium load or heavy load, impact and friction of important parts; for example, crosshead of gear, ring gear and gear shaft.
In the automotive industry, the cross-section used is less than 30mm; important carburizing parts bear high speed or heavy load and impact; for example, gears, shaft gear rings, gear shafts, sliding bearing spindles, crossheads, claw clutches, worm, etc

25CrMo4
The alloy structural steel 25crmo4 (ASTM 4118) has high hardenability, no temper brittleness, good weldability, little cold crack tendency, good machinability and cold strain plasticity.
25CrMo4 gear steel is used in general conditions or under carburizing quenching conditions, which is used for manufacturing corrosive medium with working temperature lower than 250 ℃, high pressure pipe and various fasteners working with medium containing hydrogen nitrogen mixture, higher carburizing parts and automobile gears, various special wear-resistant parts, such as aircraft, shaft, high pressure pipe and various fasteners.

42CrMo4
42CrMo4 (ASTM 4140) is a medium carbon chromium molybdenum alloy steel. Chromium content provides good hardness permeability, molybdenum element provides hardness uniformity and high strength. The alloy well balances strength, toughness and wear resistance. It has the following advantages: stable composition, less harmful elements, high purity of steel, small decarbonization layer, less surface defects, etc., and easy to process under heat treatment conditions, with good ductility and high temperature stress resistance. This material is widely used in the production of high-strength steel fasteners, such as engine, mould, motor, gear, transmission parts, shaft, gear, arm, cold forging, screw products.

In addition, ASTM 4320, 4340, 8615, 8617, 8620, 8622, 9840 (https://otaialloysteel.com/products/alloy-steel/)and so on can also be used for gear purposes. As common alloy carburizing and bearing steel, they are mainly used as materials for automobile bearings, transmission shafts, gears, screws, tool parts and other impact resistant and wear-resistant parts. The surface after carburization has high hardness, wear resistance and contact fatigue strength, while the core still maintains good toughness and can bear high impact load.

42CrMo4 steel properties

1.Description of 42CrMo4 steel

42CrMo4 steel is a kind of common alloy steel, which is usually used after quenching and tempering. It has high strength and high hardenability. The properties of 42CrMo4 round steel are better than that of 34CrMo4 steel because of higher content of carbon and chromium. 42CrMo4 alloy also has high fatigue strength and good low temperature impact toughness. The temper brittleness is not obvious.
42CrMo4 steel is a kind of high-quality quenched and tempered alloy structural steel, which belongs to high-quality low-carbon, low-alloy Cr, Mo, Ni surface hardening steel. The hardness of oil quenching and tempering is 18-22 HRC. Annealing hardening is less than 250hb. 42CrMo4 has a low carbon content range, so it has good weldability.

2.Heat treatment of 42CrMo4  steel
Annealing of 42CrMo4 alloy structural steel
Heat slowly to 872 ℃ for enough time to allow the steel to heat thoroughly and then cool slowly in the furnace. The maximum hardness of 42CrMo4 alloy steel is 250 HB (Brinell hardness).
Hardening of alloy structural steel 42CrMo4
First, the quenching is slowly heated to 880 ° C, then fully soaked at this temperature and quenched in oil or water. The tool is tempered immediately after reaching room temperature. Second quenching to 780-820 ° C followed by quenching in oil or water.
Tempering of 42CrMo4 alloy structural steel
Heat to 205-649 ° C and then cool in water or oil. The normal delivery hardness is 18-22 HRC.
Forging of 42CrMo4 alloy steel
42CrMo4 alloy steel forged at 926 to 1205 ° C (1700 to 2200 ° f)

3. Application of 42CrMo4 steel
42CrMo4 steel is characterized by high strength, high hardenability, toughness and small deformation after quenching, high strength and creep fracture strength at high temperature. The requirement of manufacturing higher strength than 35CrMo steel and the cross section of tempering forging are larger, such as large locomotive traction gear, supercharger drive gear, pressure vessel, gear, rear axle, which are greatly affected by load and spring clip link. It can be used for 2000m deep oil drill pipe joint, fishing tool, bending machine mould, etc.

4. Processing of 42CrMo4 steel
42CrMo4 plate and alloy steel round bar can be cut according to your requirements. Can also provide 42CrMo4 alloy steel grounding rod, according to your requirements tolerance to provide high quality tool steel precision grounding tool steel bar. 42CrMo4 steel can also be used as grinding plate / gauge plate of standard and non-standard sizes.

7 methods to improve the quenching&tempering process

1. Control of tempering treatment
After the mold parts are taken out from the coolant, they should not stay in the air for a long time, but should be put into the tempering furnace in time for tempering treatment. When tempering, low temperature temper brittleness and high temperature temper brittleness should be avoided. In order to eliminate the internal stress, reduce the deformation and avoid the tendency of cracking, several tempering treatments are adopted after quenching for some die parts with precision requirements.

2. Protection of quenched parts
Quenching and tempering treatment is an important link that affects the deformation or cracking of stamping die parts during heat treatment. Effective protective measures should be taken for the parts that are easy to deform or crack, such as punch and die, so as to make the shape and section of the parts symmetrical and the internal stress balanced. The common protection methods are as follows: A. packing method; B. filling method; C. blocking method.

3. Determination of heating temperature
If the quenching temperature is too high, the austenite grains will be coarse, oxidation and decarburization will occur, and the tendency of deformation and cracking will increase. Within the specified heating temperature range, if the quenching heating temperature is too low, the inner hole of the part will shrink and the diameter of the hole will become smaller. Therefore, the upper limit of heating temperature should be selected; for alloy steel, if the heating temperature is too high, the inner hole will expand and the pore size will become larger, so the lower limit of heating temperature should be selected.

4. Improvement of heating mode
For some small punch dies or slender cylindrical parts (such as small punches), they can be preheated to 520-580 ℃ in advance, and then put into a medium temperature salt bath furnace to heat up to the quenching temperature. Compared with the direct use of electric furnace or reverberatory furnace to heat and quench, the deformation of the parts is obviously reduced, and the cracking tendency can be controlled. Especially for high alloy steel die parts, the correct heating method is: preheat first (530-560 ℃), and then rise to quenching temperature. During the heating process, the time of high temperature should be shortened as far as possible to reduce the quenching deformation and avoid the production of small cracks.

5. Selection of coolant
For alloy steel, isothermal quenching or step quenching in hot bath of potassium nitrate and sodium nitrite can be used to reduce quenching deformation. This method is especially suitable for stamping dies with complex shape and precise size. The austempering time of some porous die parts (such as porous die) should not be too long, otherwise the hole diameter or hole distance will become larger. Vacuum gas quenching can also be used. When the cooling effect of gas quenching is poor, professional vacuum quenching oil is recommended.

6. Quenching treatment before WEDM
For some stamping die parts processed by WEDM, the hierarchical quenching and multiple tempering (or high temperature tempering) heat treatment process should be adopted before WEDM to improve the hardenability of parts and make the internal stress distribution tend to be uniform and in a small internal stress state. The smaller the internal stress is, the smaller the tendency of deformation and cracking is.

7. Optimization of cooling mode
When the parts are taken out from the heating furnace and put into the coolant, they should be put into the air for proper precooling, and then put into the coolant for quenching, which is one of the effective methods to reduce the quenching deformation and prevent the cracking tendency of parts. After putting the coolant into the die parts, they should be rotated properly, and the rotation direction should be changed, which is conducive to maintaining a uniform cooling rate of the parts, and can significantly reduce the deformation and prevent the tendency of cracking.

The consequences of buying inferior Cr12MoV

Cr12MoV tool steel has high hardenability. The cross section is 300 ~ 400mm. It can harden completely. It can keep good hardness and wear resistance at 300 ~ 400 ℃.

Cr12MoV can be used to make various moulds and tools with large cross section, complex shape and bearing large impact load. It has the characteristics of wear resistance, hardenability, micro deformation, high thermal stability and high bending strength. It is second only to high speed steel. Cr12MoV is an important material for die cold heading. The consumption of cold working die steel(https://otaialloysteel.com/products/tool-steel/)ranks first.

In fact, some unreliable suppliers may, regardless of the interest of the customers, cheat customers with inferior products. These dishonest actions not only disrupt the market. At the same time, it also has a serious impact on customers.

The consequences for end users who purchase these crude Cr12MoV cold work tool steels are as follows:
1) The microstructure of inferior Cr12MoV die steel is seriously segregated. Because of the poor processing performance, drilling and tapping difficulties are often encountered.
2) The deformation of heat treatment is large and the risk of cracking and bending is high. It can’t guarantee the stability of the mold size, affect the appearance of the mold and even scrap.
3) There are many impurities in Cr12MoV die steel after scrap renovation. It makes the mold produce poor red hardness at high temperature. The hardness of the die decreases quickly and the knife edge is easy to wear.
4) The purity of die steel is poor and there are many non-metallic inclusions. The impact toughness of the die is poor, and the knife edge is easy to collapse and fall.

3 KINDS TOOL STEEL

Die steel can be roughly divided into cold work tool (die) steel, hot work tool (die) steel and plastic mould (die) steel, which are used for forging, stamping, cutting and die casting. Due to the different uses and complex working conditions of various dies, the die/tool steel should have high hardness, strength, wear resistance, sufficient toughness, high hardenability, hardenability and other technological properties according to the working conditions of the die. Due to different uses and complex working conditions, the performance requirements of die steel are also different.

1.1 Cold working tool (die) steel includes cold stamping die, drawing die, drawing die, embossing die, rolling die, rolling plate, cold heading die and cold extrusion die. According to the working conditions of the tools, the cold working dies should have high hardness, strength, wear resistance, enough toughness, high hardenability, hardenability and other technological properties. The alloy tool steel used for this kind of purpose generally belongs to high carbon alloy steel, and the carbon content is more than 0.80%. Chromium is an important alloy element of this kind of steel, and its mass fraction is usually not more than 5%. However, for some die steels with high wear resistance and small deformation after quenching, the highest chromium content can reach 13%, and in order to form a large number of carbides, the carbon content in the steel is also very high, up to 2.0% ~ 2.3%. The carbon content of cold working die steel is high, and most of its microstructure belongs to hypereutectoid steel or ledeburite steel. The commonly used steels are high carbon low alloy steel, high carbon high chromium steel, chromium molybdenum steel, medium carbon chromium tungsten plutonium steel, etc.

1.2 Hot work tool (die) steel is divided into hammer forging, die forging, extrusion and die casting, including hot forging die, press forging die, stamping die, hot extrusion die and metal die casting die. In addition to the huge mechanical stress, the hot deformation die has to bear repeated heating and cooling, which causes great thermal stress. In addition to high hardness, strength, red hardness, wear resistance and toughness, hot work die steel should also have good high temperature strength, thermal fatigue stability, thermal conductivity and corrosion resistance. In addition, high hardenability is required to ensure consistent mechanical properties of the whole section. For die casting die steel, the surface layer should not produce cracks after repeated heating and cooling, as well as withstand the impact and erosion of liquid metal flow. This kind of steel generally belongs to medium carbon alloy steel, with carbon content of 0.30% ~ 0.60%, which belongs to hypoeutectoid steel. Some steels become eutectoid or hypereutectoid steel due to adding more alloy elements (such as tungsten, molybdenum, vanadium, etc.). The commonly used steels are chromium manganese steel, chromium nickel steel, chromium tungsten steel, etc.

1.3 Plastic molud steel includes thermoplastic mold and thermosetting plastic mold. The steel for plastic mould is required to have certain strength, hardness, wear resistance, thermal stability and corrosion resistance. In addition, good processability is also required, such as smaller heat treatment, better processability, corrosion resistance, good grinding and polishing performance, good repair welding performance, high roughness, good thermal conductivity and stable size and shape under working conditions. In general, hot work die steel can be used for injection molding or extrusion molding, and cold work die steel can be used for thermoset forming and high wear resistance and high strength die.

The steel grades of tool steel

2.1 Cold work tool steel
High carbon low alloy cold working die steel
9SiCr, 9CrWMn, CrWMn, Cr2, 9Cr2Mo
Wear resistant cold working die steel
Cr4W2MoV, Cr5Mo1V, Cr6WV, Cr12, Cr12MoV, Cr12W
Impact resistant cold working die steel
4CrW2Si, 5CrW2Si, 6CrW2Si
Carbon tool steel for cold working die
T7, T8, T9, T10, T11, T12
High speed steel for cold working die
W18Cr4V
Non magnetic die steel
2.2 Hot work tool steel
Low heat resistance hot working die steel
5CrMnMo,5CrNiMo
Medium heat resistant hot working die steel
8Cr3
Hot working die steel with high heat resistance
3Cr2W8V
2.3 Plastic mould steel
Carbon plastic die steel
SM45,SM50,SM55
Pre hardening plastic die steel
3Cr2Mo,40Cr,42CrMo、
Carburized plastic die steel
20Cr,12CrNi3A
Age hardening plastic die steel

Corrosion resistant plastic die steel
2Cr13, 4Cr13, 9Cr18, 9Cr18Mo, cr14mo4v, 1Cr17Ni2 in the steel plate (plate), there are many materials are included in the die steel series: 45 (45), P20, S45C, S50C and so on.