1. Welding inspection: 3 period: inspecting before welding, inspecting of the process of welding,  inspecting of product after welding.

2. Nondestructive inspection of steel welding joint

•  ultrasonic detection of defect: rate range of sound wave heared by human being is between 20HZ and 20KHZ, rate of sound wave is higher than 20KHZ is entitled ultrasonic.

• Ray detection of defect: it detects defect by penetrating through material and decaying, it devided to X ray, γ ray, high energy ray.

3 mechanical property testing for high strength bolt and combining parts

• torshearing, pre-tensile testing for high strength bolt connecting pair

Fastener bolt carried out firstly fastening and end fastening, firstly fastening adapts manual torque spanner or specialized nominal electronic spanner, value of firstly fastening should be 50% of nominal pre-tensile. End-fastening by specialized electronic spanner until quincuncial head at its end fastened down, then recorded pre-tensile.

• torque coefficient testing for high strength large hexagon bolt connecting pair.

1) Testing pre-tensile of bolt (p), wring torque of nut (T), calculating torque coefficient (k) according to formula.

2) Value of K is changing between 0.100 and 0.45,

3) Every connecting pair tested one time only without reused.

•  testing for high strength bolt connecting anti-slipping coefficient

1) Adopting double friction side conntecting with 2 or 3 bolt as tensile sample.

2) firstly wringing should be 50% of pre-tensile nominal value of bolt

3) after end – wringing, pre-tensile of bolt should between 0.95p and 1.05p.

4) drawing straight line at side of sample for observing slipping.

5) loading 10% of anti-slipping nominal loading before loading, stoping for 1min, loading steadily with speed of 3 — 5KN/s until slipping destroied, then get slipping loading.