Nitriding Steel 32crmov12-10 Tool steel

Steel Grade: DIN 32CrMoV12-10 | W-Nr 1.7765 | 32CDV12

Steel Chemical Content

Nitriding steel grades contain strong nitride formers such as molybdenum, vanadium, aluminum or chromium.

Chemical composition

Heat treatment 

Nitriding is a heat-treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. The processes are thus similar to case-hardening but performed at a lower temperature.

The advantage with nitriding is mainly the reduced distortion behavior compared to carburizing and still give a high surface strength and ductile core.

However, since the process is performed at lower temperature, the same case depth as for carburizing will take considerable time to reach.

Nitriding can also increase the corrosion resistance of a component.

Application

Nitriding steel grades Typical applications are small gears,  crankshafts  and wear parts.

Alloy steel SCM440 PLATE stocking, cutting and grinding

SCM440 Steel-JIS G4105 Alloy steel Grade 4140

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Steel Processing

we offer a range of cutting and grinding services and we find that the majority of our steel grades are supplied as cut pieces.

Whether it’s bandsaw or flame cut, black, bright or ground we can quote and supply our wide range of steel specifications to bespoke sizes and requirements, regardless of whether it’s a one-off or multiple cut pieces.

This saves you buying any material surplus to your requirements.

When enquiring please provide our sales team with full details of the sizes, quantities and specifications required.

Chemical composition of JIS alloy SCM440

Application

JIS SCM440 is commonly used in oil and gas sector. 

Typical applications as Connecting rod, Pin seam jacketed conveyor, gears, stem assembly, pump shaft and the tool holder.

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.

Engineering Steel 30crnimo8

What is Engineering Steel?-30crnimo8 steel  Alloy Stee

30crnimo8 round bar
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1.)Engineering Steel Alloying elements

Engineering Steel is a steel that has had small amounts of one or more alloying elements (other than carbon) such as manganese, silicon, nickel, titanium, copper, chromium, and aluminium added.

2. Relevant Specification for 30CrNiMo8 Material

EN 10083-3	BS970
30CrNiMo8 / 1.6580	823M30

3. DIN 30CrNiMo8 Chemical Composition 

GRADE	CHEMICAL COMPOSITION
	C	Si	Mn	P	S	Cr	Mo	Ni
		max		max	max
30CrNiMo8 / 1.6580	0,26 ~ 0,34	0,40	0,50 ~ 0,80	0,025	0,035	1,80 ~ 2,20	0,30 ~ 0,50	1,80 ~ 2,20

2.) Engineering Steel Properties

This produces specific properties that are not found in regular carbon steel.

Engineering Steels are workhorses of industry because of their economical cost, wide availability, ease of processing, and good mechanical properties. Alloy steels are generally more responsive to heat and mechanical treatments than carbon steels.

4) Engineering Steel 30crnimo8 Applications:

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!

New shipment

1045 pipe to Pakistan

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.