Seamless Steel Rail Manual Welding

Product Introduction
SINCHOLD manual welding technology regulation is apply to the welding of the butt joint of the A75 rail steel used in the production of the shore bridge and field bridge.

Product Parameter(Specification)
1.A75 Chemical Composition of Rail Steel
1.1 Typical A75 rail steel chemical composition is as follows

Note: the data in the table is mass percentage
1.2 Typical A75 rail steel carbon equivalent
CE=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15=0.71+1/6+(1.024+0.092)/5=1.10
According to the above carbon equivalent, the welding quality of rail steel is poor, and the welding operation is strictly according to the process.
2. Welding Material
This technology choose manual electric-arc welding to butt weld the rail.
2.1 Electrode is CH E507 or J507(GB E5015), J107Cr(GB E10015-G)
2.2 All of the electrodes must be baked for an hour at the temperature of 350~400ºC, and then placed in a thermal insulation box at the temperature of 120ºC after baking.
2.3 The electrode shall be used when you need it and the use by electrode tube.CHE507 or J507 electrode must be used within 4 hours. J107Cr must be used within half hour. If the electrode tube has electric heating thermal insulation function and the lead electrode is not limited by the time. Damp electrodes shall not be used during welding.
3. Joint Preparation
3.1 The docking rail shall be carried out in the workshop, after the completion of the docking puts track girders support rail beam, be moved to the outfield with girders.
3.2 Rail as far as possible the use of flat end of the supply of steel butt welding, welding and cleaning before welding clean area, to ensure that no oil, no debris.
3.3 Joint assembly as shown in figure 1 connector assembly diagram, pad under joint,size is 6×100×260mm, material is Q345 or A705-50,St52-3,pad surface must be clean, no dirt for joint clearance is 18~20mm. Use the straightedge test two track straightness alignment when assembling, after the alignment positioning on both sides available dampers in rail.
4. Preheating and interlayer temperature.
4.1 Before welding, the joints were fully pheated. The pheating temperature was 300~350ºC(see WPS-TR-01). The pheating range was 150mm for each end, and the length of the joint was 300mm.
4.2 During the welding process, interlayer temperature must remain the same as the pheating temperature, quality inspection personnel at any time by laser thermometer testing, to ensure the temperature requirements.
4.3 Interruption of the welding process, should be to pheat to 300 ~ 350ºC will continue to welding.

Figure 1 Joint Assembly Diagram

5. Welding

Rail joint welding can be divided into three parts, as shown in figure 2

5.1 Part I uses CH E507 or J507 electrode to weld, slag removal part I rapidly after welding is complete, to ensure enough interlayer temperature.
5.2 Part II still uses CHE507 or J507 to weld, transport practices is a continuous turning circle, the welding slag outflow from both sides, the welding process should pay attention to both sides of the rail to ensure full weld.
5.3 Part III uses J107Cr electrode to weld, the weld is full, after the grinding line is not visible at the bottom of the concave.
6. Heat Treatment and Heat Preservation After Welding
Immediately with flame heating at the end of the welding and the weld position of the joint is treated by post welding heat treatment. The temperature is 650 ~ 750 ºC and the time is between 15 and 30 minutes (WPS-TR-01), finally keep warm and slow cold.
7. Polishing
Before gouged out joint mat, gouged to pheat to 300ºC. carbon gouging shall not be hurt rail. Rail surface welds used special rail grinding machine, and liner in the manual polishing on both sides are to be smooth transition and uniform appearance, can use template or ruler to examine.
8. Inspection and Repair
8.1 After weld joint in welding completed 24 hours and grinding, 100% MT inspection, using local UT inspection, the result for the company's internal reference (determined by testing room inspection area and way)
8.2 For 20% of the welded joint hardness selective examination, if found to have large difference, the detection of all joint hardness, repair of large difference.
8.3 Repair
Surface crack and internal defects are found during the process of inspection, to repair in time. For surface crack can be polished to remove first, if can't polishing to remove, available carbon plane and then polished clean, but gouged and after welding must be according to the requirement for gouged and welding for fully pheat, and according to the requirements of article 6 on heat treatment after welding and heat pservation.
9. Monitoring Points
Joint pparation, pheat and interlayer temperature, heat treatment and heat pservation after welding should be strictly control quality.