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The development of non-quenched steel has gone through three stages.

The development of non-quenched steel has gone through three stages. The first generation of non-quenched steel is ferrite.Pearlite type non-quenched steel.The second generation is bainian type non-quenched steel.the third generation is low carbon martensionic type non-quenched steel.

Ferrite – pearlescent non – tempered steel.

At present, the largest amount of non – tempered steel, about 60% of the total amount.Compared with tempered steel, it has more strength than toughnes.So it is necessary to improve the toughness under the condition of guaranteeing the strength.

Development of non-quenched steel-Nippon steel

The Nippon steel researchers found,by properly controlling the production process.the austenite crystals were allowed to form a large number of ferrite nucleating cores.Then ferrite is formed not only in grain boundary, but also in austenitic crystal package.

These fine, evenly distributed ferrites make the steel remarkably more ductile.

Bayesian type non-tempered steel

It is a kind of strength and toughness is very good non quenched and tempered steel.In order to make the air cooling after forging can get bainite organization, after joined the molybdenum, manganese, boron in steel and other alloy elements.

The effect of manganese

When the content of it to a certain extent can make austenitic isothermal transformation curve is in the shape of epsilon to separate the steel C curve up and down;Boron can significantly delay ferrite transformation.

The combination of molybdenum of development of non-quenched steel

To boron or manganese – boron results in the bainite structure of steel over a wide cooling range.At the same time, manganese can reduce the phase change temperature.improve the toughness and enhance the strength.

Elements such as vanadium and chromium,they are usually added to low carbon bainitic steel,For makeing up for the decrease in strength caused,by the decrease in carbon content.

Martensioned non tempered steel

(1)

In 1988, an American steel company,first proposed the concept.third-generation non-tempered steel with low carbon tempered martensitic structure.

Similar to bainitic non-quenched steel, low carbon martensitic non-quenched steel has high toughness,as well as high strength.It has already been used in automobile walking parts and construction machinery.

(2)

At the same time, after the development and application of ferrite – pearlite (f-p), bainite (B), martensitic (M) non-quenched steel, ferrite – bainitic (F- B), ferrite – martensitic (F- M), composite phase non-quenched steel is gradually developed,and used because of low cost and excellent performance.

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The mechanical properties of non-quenched steel depend on the microstructure of matrix and the strengthening of precipitated phase.

Non quenched and tempered steel introduction

High strength steel used in rolling or normalizing state.

Its microstructure is mainly ferrite and pearlite. The method to improve the strength of non-quenched steel is to refine the structure by adding alloying elements and rolling. Silicon and manganese, which have little effect on weldability and are cheap, are often used as the main alloying elements in non-quenched steel. Controlled rolling can also refine the microstructure and improve the strength and toughness of non-quenched steel.

The typical steel types of non-quenched steel

(1) For ordinary welding structures, which are used in much the same way as mild steel, including Bridges, gas tanks, high-pressure vessels, building components, lifting machinery and civil machinery, etc.;(2) high-strength steel for shipbuilding;(3) high strength steel for gas pipelines.

Non-quenched steel are added vanadium, titanium and niobium microalloying elements

It makes it dissolve in austenite during heating because the solid solubility of vanadium, titanium, and niobium in austenite decreases with cooling. The microalloying elements vanadium, titanium, and niobium will be separated from the ferrite and pearlite in the form of nitride of fine carbides. These precipitates maintain a coherent relationship with the parent phase, strengthening the steel.The mechanical properties of this kind of steel in hot rolling, forging or normalizing state not only shorten the production cycle, but also save energy.

Non-quenched steel can be divided into non-quenched steel for hot forging

Non-quenched steel can be divided into non-quenched steel for hot forging, it’s for direct cutting, and for cold working and high toughness quenched steel. Non-quenched steel used for hot forging (such as crankshaft, connecting rod, etc.), non-quenched steel used for direct cutting is directly processed into parts with hot-rolled parts, cold-working non-quenched steel is used for standard parts (such as nuts, etc.), and high-toughness non-quenched steel is used for parts requiring higher toughness.

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Chromium-nickel-molybdenum steel: represents steel type 4340/34CRNIMO6.It has excellent comprehensive mechanical properties.

4340/34CrNiMo6

Chromium-nickel-molybdenum steel: represents steel type4340/34CrNiMo6.It has excellent comprehensive mechanical properties, high impact toughness at low temperature, low notch sensitivity and no tempering brittleness.Used for making large crankshaft, shaft, connecting rod, gear, bolt and other parts with large force and complex shape.

More application of tempering steel

(1)

Cr,ni, mo, v steel: 45CrNiMoVA for steel type.High strength, good tempering stability, oil quenching up to 60mm (95% martensite).It is used to manufacture elastic shaft and torsion shaft of heavy truck under vibration load.

(2)

Chromium silicon steel: on behalf of the steel type 38CrSi.Hardenability is better than 40Cr, the strength and low temperature impact are higher, the tempering stability is better, the tempering brittleness tendency is greater.It is commonly used to manufacture 30-40mm shafts, bolts and gears with small modulus.

(3)

Chromium molybdenum steel: on behalf of steel 30CrMoA, 4140, ML30CrMo, ML42CrMo.Water quenching 30-55mm, oil quenching 15-40mm;High mechanical properties at room temperature, high strength at high temperature and good impact at low temperature;No tempering brittleness.Used for making parts with large section, bolts and gears with high load and flanges and bolts under 500℃;Conduit and fastener under 400℃.4140 has higher hardenability than 30CrMoA and is used for making parts with higher strength and larger cross sections.

(4)

Chromium manganese molybdenum steel: on behalf of the steel 40CrMnMo.The diameter of oil quenching is 80mm, with high comprehensive mechanical properties and good tempering stability.Used for manufacturing heavy load gear and shaft parts with large section.

(5)

Manganese molybdenum vanadium steel: on behalf of the steel 30Mn2MoWA.Good hardenability: water quenching up to 150mm, the heart structure is upper and lower bainite plus a small amount of martensite;Oil quenching 70mm, more than 95% martensite in the heart;Good low temperature impact toughness, low notch sensitivity and high fatigue strength.It is used to manufacture important parts under 80mm.

(6)

Chromium manganese silicon steel: on behalf of the steel 30CrMnSiA.Water quenching 40-60mm (95% martensite), oil quenching 25-40mm.High strength, impact toughness, temper brittleness.Used for manufacturing high pressure blower blade, valve plate, clutch friction plate, shaft and gear.

(7)

chrome-nickel steel: on behalf of the steel 40CrNi and 45CrNi.Water quenching up to 40mm, oil quenching up to 15-25mm;Good comprehensive mechanical properties, good low temperature impact toughness, little tempering brittleness.30CrNi3A has high hardenability, good comprehensive mechanical properties, white point sensitivity and temper brittleness.Used for making large section of crankshaft, connecting rod, gear, shaft and bolt.

Ms Sharon Wan

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1.2083 AISI 420 plastic mold steel is German DIN standard grade 1.2083, American AISI standard grade is 420.

1.2083 AISI 420 mold steel is suitable for electric corrosion operation, suitable for acid plastics and molds that require good polishing. It is mainly used in the production of PVC molds, wear resistance and filling molds. It is including thermosetting plastic molds, long-life molds. Such as: disposable tableware molds, optical product parts production, like cameras and sunglasses, medical containers, etc. .

Now this plastic mold steel 1.2083 AISI 420 is very hot popular in China because it is widely and hugely applied on the different mold tools. And the mold tools will be used on the different medical machines.
The epidemic is spreading rapidly around the world, which has a huge negative impact on global public health security. The global crisis seemed to bring the world into the long night. There is no borders on the virus.

Facing the epidemic situation, it is imperative for all countries to strengthen cooperation. Governments of various countries need to learn some experience. Like take strict detection and tracking measures, actively share knowledge about epidemic prevention and control. And establish temporary hospitals, allocate resources to the places where they are most needed through monitoring. Developed countries should consider providing assistance to developing countries and countries with weak public health systems when possible. The international community should work together to reduce the infection rate so that the medical system can effectively respond to the outbreak. Then make vaccines to be developed, and allow patients to receive timely and appropriate treatment.

Each piece of dark cloud is inlaid with gold. Despite the negative impact of the epidemic, we still have to see positive results. Over the past few years, global conferences have continually called on countries around the world. That is to work together to meet the challenges posed by climate change. But some countries are not attentive. After the outbreak of the New Coronary Pneumonia, many countries have adopted “closing the city” measures. It gives us the opportunity to think more deeply about the impact of humans on the planet and take effective measures in time to protect the common homeland of humanity.

Now it is the time for mankind to work together to create a common vision. This vision will promote people’s mutual concern and arouse people’s concern for the entire planet. If human beings expect to have a bright future, they must work together. When fighting against the epidemic, even if it falls into the long night. As long as the light of the community of human destiny shines, we can fill the world with warmth and love through solidarity and cooperation.
Otai undertakes every order to the end and solve customer’s problem without any hesitate on responsibility. That is why OTAI is professional in the special steel line for more than 21years.

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34CrNiMo6 Intorcution –classification and chemical analysis

34CrNiMo6 Introduction –classification and chemical analysis

classification:

① quenched and tempered structural steel

②Surface hardened structural steel

① The carbon content of quenched and tempered steels is generally about 0.25% to 0.55%. For structural parts of a given cross-sectional size, when quenching and tempering along the cross-section during quenching and tempering (quenching and tempering), the mechanical properties are good. If it is not quenched and free ferrite appears in the microstructure, the toughness decreases. For steels with a tendency to temper brittleness, such as manganese steel, chromium steel, nickel-chromium steel, etc., they should be cooled quickly after tempering. The critical quenching diameter of this type of steel increases with the increase in grain size and alloying element content. For example, 40cr and 35simn steel is about 30-40mm, and 40crnimo and 30crni2mov steel is about 60-100mm, which is commonly used in manufacturing Structural parts such as shafts and connecting rods with large loads.

②Surface hardened structural steel is used to manufacture hard and wear-resistant surface parts and flexible parts, such as gears and shafts. In order to increase the toughness of the core of the part, the carbon content in the steel should be low, generally 0.12 to 0.25%, and there is also an appropriate amount of alloying elements to ensure proper hardenability. Nitrided steel also needs to add alloy elements (such as al, cr, mo, etc.) that are easy to form nitrides. Carburized or carbonitrided steel, after carburizing or carbonitriding at 850 ～ 950 ℃, quenched and used under low-temperature tempering (about 200 ℃). The nitrided steel is directly treated by nitriding (480 ～ 580 ℃), and it is no longer quenched and tempered.

34CrNiMo6 (1.6582) belongs to European standard high-strength alloy structural steel.

According to the carbon equivalent calculation formula recommended by the International Welding Society (IIW) Ceq = C + 1 / 6Mn + 1/5 (Cr + Mo + V) +1/15 (Ni + Cu) (%)

(1) When Ceq <0.40%;

(2) When Ceq = 0.40 ～ 0.60%, the hardening tendency of the steel gradually becomes obvious, and the weldability is acceptable. When welding, appropriate preheating before welding and slow cooling after welding should be adopted to control its welding line energy;

(3) When Ceq> 0.60%, the steel has a strong hard tendency and poor weldability. It is a steel type that is more difficult to weld, and a higher preheating temperature and strict process measures must be taken to select suitable welding. material. It is calculated that the carbon equivalent value of 35CrMo steel Ceq = 0.72%.

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Our OTAI stocks 1.7225 42CrMo4 steel plates and keeps daily inventory of 1000tons. We are the biggest stockiest in south of China.

As this item is our hot selling items, we exports this 1.7225 42CrMo4 to more than 35 countries from EU, Middle East and Asia. The steel materials meet DIN, ASTM, EN, JIS and so on in different international standards.

Now as the virus affect, the material for this 1.7225 42CrMo4 and the DC53 steel material became the internet hot selling material now. Because the 1.7225 42CrMo4 is for the mask mold tool apply on the normal mask manufacturing.And the DC53 is for the mold tool using on the N95 mask manufacturing.

What we learn from this virus? 

And recently, I saw some report and news about the blame games for this virus. Sometimes, as the human being, we should learn something from this virus lessons. Sometimes, we underreact and in other situations we overreact, and for a reason. Facing the coronavirus, China, Japan, EU and USA all struggles, although for different reasons. China worried about sounding a false alarm and causing panic in January. When they knew little at the very beginning, by the time of the Wuhan lockdown, there were only 570 documented cases and 17deaths. These numbers were alarming but not very illuminating. The Chinese chose to overreact, they closed off an entire province, the size of Portugal and Hungary put together. But a month of data should have made a huge difference.

In late Feb many countries chose to underreact, they had other things to worry about. The Japanese did not want to delay the Olympics. The Europeans doubted the necessity to change their way of life. And the Americans hated to shut down what is the biggest world economy. Should we blame them? Maybe. But is is always easy to judge with the benefit of hindsight. Foresight is totally another thing. You could be right and you could be wrong.

Donald Trump said : I am instructing my administration to halt funding of the World Health Organization . While a review is conducted to assess the World Health Organization’s role in severely mismanaging and covering up the spread of the coronavirus.Today, America blamed the WHO for doing too little too late. In 2009, the WHO was also blamed but for a different reason. It was criticized for overreacting. The swine flu that originated from a Mexico farm was declared as a pandemic. Because it looked like and acted like one. It turned out to kill only 0.01 percent of the infected, lower than a seasonal flu. And the world paid a huge sum of money and human resources to contain it. People blamed the WHO for overshooting. To be continued…

Ms Phoenix Li

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As recently, the 4140 flat bar and other bars orders are increasing heavily. And for increasing the speed and capacity on the cutting flat bars, our company added a new big Vertical Sawing machine. The speed and efficiency is double more than the before normal cutting machine.

And usually, our company will make the stock for our running item 4140 steel plates. When we received the official order , we will arrange to cut it into 4140 flat bar as request. So normally, customers are very happy to have the one stop solution service from us. As we have our own cutting machine, milling, grinding equipments or even the testing. It really makes them without any worry. Our OTAI not only could supply the 4140 flat bar, but also other different steel material like tool steel, high speed steel in flat bars, round bars.

In last chapter, we talked about what we learned from the virus, now let’s continue to the next.We are all humans and we are susceptible to making wrong calls, especially with limited data and unlimited stress. The fact of the matter is our science is only as good as the data we have. In the early hours, we simply don’t have good data. Scientists know it, but the public don’t. We expect clarity and simplicity. But it unfortunately is a bridge too far in the land of a new virus. To make matters worse, the impulse to think of the world as a place with simple answers,may get us into rounds of blame games.

People say things like the virus exists because the Chinese eat bats. The spread is because somebody hid the information. That sound right and make you feel vindicated, but they are not real reasons. But there is a peril in buying into these simplistic messages. It stops us finding our own blind spots.If the Chinese are not humble, they would fail to upgrade the early warning system. If the Europeans are too proud, they would not appreciate the merits of a strong union. If the Americans are obsessed with being first, they would be the last to fix the broken public health system.

The blame game does not help at all. It blows things out of proportion.And it skews our understanding without our knowledge. It denies us the chance to be better and wiser. A pandemic like this has happened before, it is happening now and will happen again. And our human response may not be perfect. But we are better every time because we learn.Humans have beaten the small pox and SARS. We have a good chance to beat this one. But it takes time and most importantly it takes all of us to be honest and humble.

And there is only one thing that can make us honest and humble. That is truth backed by data and science. Data says what medicine works, not politicians. Data says where the virus came from, not senators. And scientists say don’t have enough data yet. The real truth has no regard for what you think and who you are. That may make us uncomfortable. But if you are brave enough, you will accept the world as it is, not as you want it to be.

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Otai company provides the DC53 die steel for the mask factory. We will provide a premium mask mold to meet the demand for mask manufacturing.

Today is Monday, the first day of a new week, I am wondering what to share with customers. Our company locates in Dongguang city, Guangdong province. The weather turns to be hot. Because of the pandemic, we also have to wear the mask every day to control the spreading of the virus. However, I read a news that many people gathering beside the beach without wearing a mask. It is very dangerous, I hope the days without wearing a mask will come soon. Otai company provides the DC53 die steel for the mask factory. We will provide a premium mask mold to meet the demand for mask manufacturing.

Although almost five-month past, the virus doesn’t disappear. The hottest days are around the corner. Although it is un-convenient for us to keep social distance, wearing a mask. However, we have to keep doing this to shorten the hard times. Even though the virus is under control in China, most of the people still keep the masks. The new arrival of DC53 die steel is still popular at our company. We are busy producing the mask mold every day. We not only provide the N95 mask mold but also provides the Ultrasound parts for mask mold. As we have talked before, DC53 steel is a good choice for mask mold manufacture. The quality is better than other materials.

Properties of DC53 die steel

Cold work DC53 die steel overcomes the insufficient of SKD11 high-temperature tempering hardness and toughness of weakness, DC53 tool steel will fully replace SKD11 tool steel in the field of general and precision mold. Its toughness is 2 times of SKD11, DC53 toughness is more prominent in the cold work die. Made of DC53 tools steel rarely appears crack and craze, greatly improving the service life.

The DC53 steel has a uniform distribution of fine carbides. It has great galling and wears and fatigue resistance. It has also a High temper resistance to support PVD & nitride surface treatments. And it has Machining and grinding properties are superior to most other tool steels.

Hoping the day we can freely go outside without wearing a mask, if you have demand about the mask mold, please feel free to contact me.

Mr Jack Tan

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how to improve the lifetime of die made of the 1.2344 die steel ? We can talk about it from the improvement of the heat treatment.

2. Heat treatment strengthening of 1.2344 die steel

The main structure of 1.2344 die steel in the annealing state is pearlite. and its performance is not up to the requirements of the mold. so it must be hardened and tempered to improve its overall performance.

In the quenching stage, the steel is heated above the austenitizing temperature. and then the steel is cooled with a greater degree of supercooling to obtain the hardened martensite structure. In the tempering stage, the steel is reheated to the austenitizing temperature. and the hardened martensite structure is transformed into a tempered martensite structure, to improve the comprehensive properties of the steel.

1) the quenching phase of 1.2344 die steel

Through the metallographic analysis of a large number of dies with premature failure, it is found that the coarse austenite grain is one of the important reasons leading to the premature failure of dies. The thickness of austenite grain is directly related to the service life of the die.

The larger the grain size, the greater the tendency of cracking and distortion during quenching. Therefore, the austenite grain size must be controlled effectively.

The original structure and thermal conditions of steel will affect the austenite crystal. Therefore, in the quenching phase, to obtain fine grain austenite, it is necessary to strictly control the heating temperature and holding time.

2) tempering stage of 1.2344 die steel

After the steel is hardened, there will be greater internal stress. The purpose of subsequent tempering is to remove the internal stress and make the metastable structure stable.

Too much residual austenite will reduce quenching hardness and embrittlement will occur during use due to aging deformation (transformation into martensite). General primary tempering can not reduce the residual austenite to a reasonable level. In actual production, secondary tempering is used, the tempering temperature is usually about 590℃, and air cooling.

Since martensite is formed during rapid cooling, air cooling occurs after each tempering to create a temperature gradient that allows the residual austenite to be transformed more thoroughly. After the second tempering, the hardness of the workpiece is maintained at HRC 47-50 to ensure that its performance meets the requirements.

The quality control of die steel is very important, it affects the life of die, product quality, and production efficiency.

Mr Jack Tan

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