HOW THE GREAT WALL OF CHINA WAS BUILT? BASIC INFORMATION

GREAT WALL OF CHINA CREATION BASIC INFORMATION
The Creation of the Great Wall of China

Who Built the Great Wall When and Why
Parts of the Great Wall were first built by princes and overlords in the Seventh Century BC as regional border defenses when China was divided into many small states. After the unification of China in the beginning of the Qin Dynasty (221-206 BC), the China's first emperor, Qin Shihuang (you must have heard of his Teracotta Army), linked the walls of the three states in the north (Qin, Zhao and Yan). This formed the first "Wan Li Chang Cheng" (ten thousand li Great Wall, li is a Chinese unit of length, 2 li = 1 km). Read more...

How was the Great Wall Built?
Twisting and turning up mountain and down valleys, the great wall, is really a marvelous civil-engineering project in ancient times. at the time relying solely on the manpower with no help of machinery at all, except such animals like donkeys and goats which were used to carry stone and earth up hills and down dales, it was relly an unimaginably difficult job to carry out such a huge project. Read more...

How Was the Great Wall of China Made?
Construction of the Great Wall of China began around 700 B.C. During this time, China was divided into seven different lands, which began building walls to protect themselves from one another. Within 500 years, the walls stretched over 3,000 miles. About 200 B.C., the Chinese states were united for the first time under Emperor Qin, who began the process of connecting the many different walls to protect China from northern invaders. Read more...

Construction of the Great Wall of China
The final result of the largest construction project in history to be put into effect was a twenty five foot high, twenty foot wide, and over 1500 mile long wall, called The Great Wall of China. The Great Wall of China was made of ear th and stone and was built to protect China from northern invasions. Read more...

WELDING RODS QUESTIONS AND ANSWERS

TUTORIALS ON WELDING RODS
Welding Rod Info


1. The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before?

H4R is an optional supplementary designator, as defined in AWS A5.1-91 (Specification for shielded metal arc welding electrodes). Basically, the number after the "H" tells you the hydrogen level and the "R" means it's moisture resistant.

"H4" identifies electrodes meeting the requirements of 4ml average diffusible hydrogen content in 100g of deposited weld metal when tested in the "as-received" condition.

"R" identifies electrodes passing the absorbed moisture test after exposure to an environment of 80ºF(26.7ºC) and 80% relative humidity for a period of not less than 9 hours.

The H4R suffix is basically just additional information printed on the rod, and does not necessarily mean a change in an electrode previously marked E7018.

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2. Why is hydrogen a concern in welding?

Hydrogen contributes to delayed weld and/or heat affected zone cracking. Hydrogen combined with high residual stresses and crack-sensitive steel may result in cracking hours or days after the welding has been completed.

High strength steels, thick sections, and heavily restrained parts are more susceptible to hydrogen cracking. On these materials, we recommend using a low hydrogen process and consumable, and following proper preheat, interpass, and postheat procedures. Also, it is important to keep the weld joint free of oil, rust, paint, and moisture as they are sources of hydrogen.

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3. What is the maximum plate thickness which can be welded with Innershield® NR®-211-MP (E71T-11) wire?

NR®-211-MP is restricted to welding these maximum plate thicknesses:

Wire Diameter Maximum Plate Thickness
.030"(0.8mm) 5/16"(7.9mm)
.035"(0.9mm) 5/16"(7.9mm)
.045"(1.1mm) 5/16"(7.9mm)
.068"(1.7mm) 1/2"(12.7mm)
5/64"(2.0mm) 1/2"(12.7mm)
3/32"(2.4mm) 1/2"(12.7mm)
For thicker steels, look to Innershield® NR-212. It has similar welding characteristics to NR®-211-MP but is designed for use on materials up to 3/4" (19.1mm) thick.

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4. What electrode can I use to join mild steel to stainless steel?

Electrode selection is determined from the base metal chemistries and the percent weld admixture. The electrode should produce a weld deposit with a small amount of ferrite (3-5 FN) needed to prevent cracking. When the chemistries are not known, our Blue Max® 2100 electrode, which produces a high ferrite number, is commonly used.

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