Rail Grinding Works- That Is Enough To Know

Rail grinding works- that is enough to know

The rail shall be polished before the high-speed railway is opened to traffic. This grinding strategy is called pre grinding. It is not only high-speed railway. Generally, after the new line is completed, the rail shall be polished before operation. Its purpose is to remove the rolling scar, decarburization layer, welded joints at rail butt joints and improve the surface roughness. The ultimate purpose is to eliminate the bad traces on the rail surface, Prevent the further development of these defects and improve the service life of rail.

In addition to pre grinding, rail grinding strategies are also divided into preventive grinding, maintenance grinding (also known as maintenance grinding) and repair grinding (also known as corrective grinding).

When it comes to rail grinding, we have to talk about rail diseases first. We all know that locomotives such as high-speed rail, bullet train and subway have no steering wheel. Drivers do not need to operate the direction. They guide the vehicle completely through the steel rail, so the steel rail carries the huge pressure and impact force from the wheel.

Under extremely complex working conditions, various damages will inevitably occur, including defects in smelting process and damages in transportation, construction and use. Common damages include rail wear, including vertical wear, side wear and wavy wear (wave wear for short); Contact fatigue damage: including rail head crack, hidden damage and peeling; There are fat edges and rail scratches.

Some rail damages are shown in the figure below:

Side grinding

Wave Grinding

Hidden injury

crackle

Fat edge

Scratch

All these are "diseases", which will increase wheel rail noise, accelerate the deterioration rate of vehicle components and track components, and aggravate the further expansion of rail diseases. The main reason is that they destroy the best contour shape of the rail and change the wheel rail contact state.

What is the best profile? As shown in the figure below, when the train runs on a straight line or a large radius curve, the wheel tread contacts the rail head area B. in this state, the contact stress and transverse creep force are the minimum; When the rim is close to the rail gauge angle, i.e. area C in the figure, the contact stress is the smallest when conformal contact is formed. If it is a disease, it must be treated. The way is to perform surgery - rail grinding. Rail grinding is actually cutting the rail surface, removing diseases and restoring the rail to the best profile.

Wheel rail contact function area

Two point contact single point contact conformal contact

The rail head profile is similar to an arc shape, but the actual grinding (grinding wheel grinding) is to divide the rail head into different areas according to the angle, that is, the rail head profile is regarded as a line segment divided by the angle, and the position to be polished corresponds to a certain angle.

Therefore, the grinding equipment specifies different parts of the polished rail by controlling the deflection angle of the grinding head, as shown in the following figure.

Obviously, the more serious the rail damage, the greater the amount of grinding and cutting, the greater the amount of operation, the greater the difficulty, and the reduced rail life. Therefore, repair grinding and repair grinding are like "treatment", and the best way is to prevent rail "illness", that is, regular preventive grinding to completely eliminate the damage in the germination state.

The following figure shows the initial crack characteristics and crack propagation. The thickness of the plastic flow layer is generally 0.2mm. Therefore, preventive grinding does not require a large amount of rail cutting, which is generally between 0.1-0.2mm. In this way, it can prolong the service life of rail without too much cutting, which is the most economical and effective way.

According to the data, regular preventive grinding of steel rails can prolong the service life of 5-8 years, improve train operation, maintain passenger comfort, reduce snake movement, reduce noise, reduce energy consumption, reduce the maintenance cost of locomotive parts and tracks, and bring economic and social benefits.

The following figure shows the impact of preventive grinding and repair grinding on the rail life. The yellow line indicates preventive grinding. Each grinding will delay the speed of damage development and improve the rail life. Preventive grinding when the micro crack does not exceed 0.2mm is the best time to block the accelerated damage trend of rail.

Next, there are three ways to realize rail grinding: sliding shoe grinding, grinding wheel grinding and milling.

Sliding shoe grinding is to grind off the rail surface layer by pressing the grinding stone on the rail for reciprocating movement. This grinding method can only grind the rail head longitudinally, can not adjust the rail profile, and can not grind the turnout. Therefore, this grinding method has been phased out and the grinding speed is low.

Grinding wheel grinding usually uses the high-speed rotating grinding wheel driven by motor or hydraulic motor to grind the steel rail. This is an active grinding and is the main grinding method at present. The steel rail is polished longitudinally and transversely.

There is also a passive grinding. The position of the grinding wheel is inclined to a certain angle with the running direction of the train. The high-speed operation of the power tractor drives the grinding wheel to rotate at high speed on the steel rail. The relative motion between the grinding wheel and the steel rail reaches the required material grinding speed, and the whole rail head from the running edge of the steel rail to the running surface is polished. This grinding method is because of the fast grinding speed, Therefore, it is called rail high-speed grinding.

Grinding wheel grinding

We, Jinzhou Tiegong Railway Maintenance Machinery Co.,Ltd manufactured many kinds of rail gringding machine to suit variety of track bruise. 

GM-2.2 Electric Rail Grinding Machine 

NGM-4.8 Digital Display Rail Grinding Machine 

 NGM-4.4 Rail profile grinding machine.（The best helper after thermit welding）

Passive grinding

Milling is a new rail profile repair operation mode. The milling cutter is installed on the radial surface of the milling wheel. Each milling section is equipped with several milling cutters. There are several milling sections in a circle of the milling wheel, so that all milling cutters form a rail head profile to be completed.

At present, most of the domestic rail grinding equipment are imported from foreign technology, which has basically completed the process from scratch, from complete import to localization, but there is still a gap with the rail grinding technology in Europe and America.

High speed rail is a systematic project, not only construction and operation, but also maintenance. It involves many aspects. Although remarkable achievements have been made, we also recognize the gap. It will take time to catch up with and surpass in an all-round way.