Great warships

Chapter 61 High Strength Steel

Those who came were old acquaintances, Pang Jianmin and Zhang Zhen. Their warship did not go to sea, but was moored in the port. After getting the news, the two came by car. The old Jiefang boarded behind them, and a group of sailors were also sitting on the submarine. , is a pass inspection.

However, luck is not always there. The torpedoes similar to last time are gone. He just found some submarine devices at random. Qin Tao was not very generous, so he just gave them to them.

However, the two did not leave. After checking the submarine, even though the sun had already set in the west, the two still walked around the shipyard, and soon fell in love with the batch of steel plates that Liu Ming had just sent.

"Isn't this too thin?" Pang Jianmin couldn't help but said.

"Everyone is used to taking big boats. Look, ordinary speedboats are actually steel plates of this thickness. The anti-smuggling speedboats we built for the customs are also of this thickness."

"That's different. The catamaran passenger ship to be built next must meet military standards." Zhang Zhen said.

Qin Tao smiled: "Of course I know, military standards, the quality is absolutely outstanding, I have a steel inspection report here, do you want to see it?"

"The yield is 520 MPa, which is higher than our 945 steel. How is this possible?" Zhang Zhen was surprised when he saw the report for the first time.

Yield strength is an important index to measure steel. In professional terms, yield strength is the yield limit when the metal material yields, that is, the stress that resists micro-plastic deformation.

To explain in simple words, it is the strength of the material. For example, the yield limit of low-carbon steel is 207 MPa. When the external pressure is greater than this value, the parts made of low-carbon steel will produce permanent deformation. If it is smaller than this, the part will return to its original shape after the external force is removed.

The greater the yield strength, the greater the ability of the material to resist external forces and the higher the strength.

For ordinary civilian ships, two to three hundred MPa of marine steel is enough, but warships must be stronger.

Back then, when we had a close relationship with Lao Maozi, Big Brother exported special marine steel. After the relationship broke down, the country could only grit its teeth and conduct research and development on its own. First, it imitated Lao Maozi's marine steel and developed a batch, such as Say 907, 921 and other steels, but these steels imitate the composition of Lao Maozi, which contains a lot of nickel and chromium.

Lao Maozi’s Ural Mountains are rich in nickel ore and chromium ore, but there are few in China. Therefore, nickel-chromium-free or low-nickel-chromium steel should be developed in China.

In the past few years, the domestic situation was complicated. The quality of the steel produced was very poor, and there was even an accident (the steel used for a certain submarine was unexpectedly unqualified). After entering the 80s, domestic steelmaking enterprises began to spend a lot of energy on research and development.

Firstly, the 390 MPa 907A steel was developed. Last year, the 440 MPa 945 steel with better seawater corrosion resistance and low temperature performance passed the appraisal. As for the model still under development, there is 785 MPa VHD402 steel . (This steel passed the appraisal in 93 and was named 980 steel.)
The ships currently being built by the Navy only use 440 MPa-grade 945 steel, but here, a new type of steel with a yield of 520 MPa appears. How can it not be surprising? (It seems that the yield of 921A steel used in nuclear submarines is not low, but I didn’t find too much information, so I ignored it.)
Qin Tao secretly laughed in his heart, is this still high?This is already low enough, okay? After all, Mingzhou Shipyard has limited technology, so after returning the AK-590 steel with a yield of 25 MPa, only 520 MPa is left.

You know, even Varyag uses this kind of steel. (Except for the deck, which is a 700 MPa AK-27.)

Hearing Zhang Zhen's doubts, Qin Tao rubbed his nose: "Are you suspecting that the test report is fake? When we cut the steel, you can take a piece of leftovers and go to any department for appraisal."

"No, no, of course not." Looking at the stamp of the professional testing organization on it, Zhang Zhen shook his head again and again: "I just feel a little incredible, where did you buy it from?"

"Our Mingzhou Iron and Steel Works." Qin Tao said: "The quantity of this batch of steel is not large, and we give priority to supplying it for our own use. If outsiders want to buy it, they have to queue up."

Mingzhou Shipyard, not many?Looking at the three whale-like submarines in the distance, Pang Jianmin suddenly thought of something: "Could it be you?"

"Why not?" Qin Tao smiled.

Zhang Zhen also suddenly realized.

"If we don't use high-strength steel, we need to use aluminum to reduce the weight. If we use aluminum, the construction cost will soar, and our contract has to be revised."

This is another reason why Qin Tao uses high-strength steel.

Most of the speedboats like to use aluminum to build them, including the few anti-smuggling speedboats they purchased from island countries. The design drawings are made of aluminum, so as to reduce weight.

However, the current Mingzhou Shipyard has no experience in using aluminum, and it is expensive, so Qin Tao temporarily replaced it with high-strength steel. Steel with a yield of 520 MPa is definitely better than aluminum. use!

"No need, no need." Zhang Zhen quickly waved his hands, don't mention money, you can still be good friends without mentioning money.

"Well, the contract will not be amended, but I hope that your funds will be in place as soon as possible. We will start construction soon. There are many places that need money, especially the two planned high-power diesel engines, which need to be ordered quickly." Qin Tao still had to press for money.

The money is not in place, how to start work?
"The two main engines must be purchased from abroad? Can the diesel engine of the missile boat made by ourselves be used?" Pang Jianmin asked.

"Yes, if we use domestic diesel engines, we can save a lot of money." Zhang Zhen also said beside him.

"Of course not." Qin Tao said: "Our domestic diesel engines are currently used on missile boats by the K711E48ZC two-stroke diesel engine mainly developed by the 150 Institute. Although the power has reached 5100 horses, it is equal to the Soviet M50-4. Power, however, it is still not enough for my design index, can not reach the design speed, moreover, this is a two-stroke diesel engine, the fuel consumption is very high, we are going to build a cruise ship, if the fuel consumption is too high, the customer will not accept it.”

"The MTU V16 396 TE74L power diesel engine I plan to use can output 6800 horses each, which is 40.00% larger than the domestic engine, so that it can reach the design speed. What you are most interested in is the high speed I mentioned. If the test voyage If the time is not reached, you should blame me again."

Qin Tao looked at the two people in front of him: "This is the most commonly used marine diesel engine in the world. Although we have to import it now, we will definitely be able to make it domestically in the future. At that time, we don't need to modify the design. Isn't this a multi-purpose engine? Don’t be afraid to spend money now.”

　PS: MTU represents the manufacturer of the diesel engine, 16 represents 16 cylinders, V represents the cylinder layout is V-shaped 90 degrees, 396 represents a single cylinder displacement is 3.96 liters, T represents turbocharged, E represents the use of fresh water to cool the charge air , which is supercharged intercooler, 4 stands for design index, and L stands for improved.The hero of East China wasted a lot of effort to find the model of the engine of this speedboat, and I don't know if it is right.

　
(End of this chapter)