Embroidering with steel: Zhang and his journey to improve China's shipbuilding

Zhang Dongwei is one of the 16 workers in China to master the welding technique on invar steel, the core technology for the manufacturing of LNG (liquefied natural gas) ships.

Zhang Dongwei is one of the 16 workers in China to master the welding technique on invar steel, the core technology for the manufacturing of LNG (liquefied natural gas) ships.

Personal profile

Zhang Dongwei was born in Shanghai’s Zhoupu Town in December of 1981. He is among China’s first batch of 16 workers to master the welding technique on invar steel, the core technology for the manufacturing of LNG (liquefied natural gas) ships.

Zhang has participated in the construction of 18 LNG ships in the last 13 years since he acquired the welding skill. 

It takes more than two hours to manually weld a 3-meter-long invar steel. He describes his work as “embroidery on a steel plate,” which requires fine skills. After doing the job for 17 years, Zhang has become quite familiar with the technique. He said his mind becomes clear and concentrated once the welding gun is lit.

In the past years of reform and opening-up, Zhang and his colleagues have been trying to improve the manufacturing process of China’s domestically developed LNG vessels. Among the LNG ships manufactured by the Hudong-Zhonghua Shipbuilding (Group) Co., over half of the facilities and ship parts have been domestically made. Zhang aims to raise that to 100 percent.

Zhang Dongwei demonstrates a key welding technology

My story

Since acquiring the welding skill of the cargo containment systems for LNG carriers, I have participated in the construction of 18 LNG ships in the last 13 years. Among them, 17 ships are still sailing around the world. I am Zhang Dongwei, the leader of an electric welding team of the Hudong-Zhonghua Shipbuilding (Group) Co. I am also one of the nation’s first batch of 16 workers to master the welding technique on invar steel, the core technology for the manufacturing of LNG ships.

I was born in December 1981. After graduating from the senior technical school of the shipbuilding group in 2001, I was recruited by the group as an electric welder. During my 17 year career, I deeply feel that during the decades of reform and opening-up, the technical standard of China's shipbuilding industry has been continuously improved, and the techniques have become more advanced. The products manufactured by our company have evolved from low-value-added hulls such as bulk carriers, to high-tech, difficult and high-value-added vessels. Some of the products have filled in gaps of the country’s shipbuilding industry. In the process of China's reform and opening-up, our shipbuilding industry also occupies an important place in the world. I feel proud to be part of the industry.

In the years of reform and opening-up, I am also pleased to witness that the manufacturing equipment in the factory is constantly updated and has become more advanced. At the same time, the skills of our industrial workers are also improving. Hundreds of workers in China have obtained invar steel welding certification. Some newly recruited graduates in our workshop have learnt about advanced intelligent equipment such as welding robots at school.

I am most proud of the fact that I am involved in the manufacturing of LNG ships, one of the world's most advanced vessels, and that I've helped to improve the nation’s shipbuilding ability. We continue to explore the improvement of the manufacturing processes to promote domestically developed LNG carriers.

LNG ships are extremely demanding in terms of manufacturing technology and safety performance. If a gas leak occurs, the ship will explode. Currently, only a few countries can build LNG ships. The core component of the ship is the cargo tank containment system, which is made of a kind of special steel – the ultra-low temperature resistant invar steel. The steel plate is as thin as business card paper. Most of them are only 0.7 millimeters thick and will easily become corroded. Currently, the steel mainly depends on imports and its price is rather expensive. A super LNG ship is welded with millions of these invar steel plates in various shapes. It requires supreme welding skills to ensure the tightness and strength of the steel.

The invar steel plate welding technology is patented by French LNG ship technology giant GTT. In 2005, I was selected to participate in the first batch of invar steel welding G certificate training and examination. At that time, I deeply felt the urgent desires and needs of the country to manufacture its own LNG ships. I also became determined to take the chance to improve my skills. I successfully obtained the certificate thanks to my basic skills and strong psychological quality. From that year, China’s first home-made LNG ship began being manufactured at the Hudong-Zhonghua shipyard.

When building the first domestically developed super LNG ship named “Da Peng Hao,” the environment for invar steel welding was quite ideal. The cabin was kept at a constant temperature of 25 degrees Celsius and the humidity was lower than 50 percent. But it was still a challenging mission and requires supreme techniques. Invar steel is too thin as well as being easily damaged and rusted. It can be corroded just by the welders’ hand or sweat. I must be particularly cautious to ensure quality.

The total welding length of invar steel for a super LNG ship is about 140 kilometers. Though 90 percent of the welding process is completed by machine, the remaining 10 percent is the most complicated and requires manual work. It takes over two hours to finish welding a three-meter-long steel plate. It is like embroidery of steel — each “needle” must be delicate and secure. I have become quite familiar with the technique. There is no other thinking in my mind but to accomplish the mission perfectly once the welding torch is lit.

Zhang Dongwei explains automatic welding equipment

After the welding is completed, the steel compartments must pass a leak test. A professional third-party company will be invited to check the compartment by filling it with helium. A ship hull has four cabins and the number of leakages in each cabin must be no more than 10 to pass the check. The leaking areas can be repaired but that will cost the company several million yuan. We demand of ourselves that no leakages occur on the whole ship.

Among the LNG ships manufactured by the Hudong-Zhonghua Shipyard, over half of the GTT-certified facilities and ship parts have been domestically made. We aim to make the whole vessel completely in China.

We spent 36 months welding the invar steel for the core confined cabin of the “Da Peng Hao.” Nowadays, the welding schedule for a ship in the same-class can be reduced by half.

The original load of the ship hull was 147,000 cubic meters, and now it has been upgraded to 174,000 cubic meters. Standing at a new starting point for reform and opening-up, my colleagues and I will work harder, strive for excellence in craftsmanship and face the challenges we come across. We are determined to build more advanced ships, and constantly “unlock” new shipbuilding technologies.

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