Titanium pipe and steel composite tube sheetexpand junction process and by TIG welding process. And by ammonia refrigeration device manufacturing practice proved that titanium tube and a titanium steel composite tubesheets in choosing the reasonable manufacturing process can obtain high quality welds, and titanium and titanium steel composite plate for thermal equipment manufacturing has accumulated certain experience.

Titanium is a kind of active element, which can maintain high stability and corrosion resistance with oxygen at room temperature. The oxide film formed above 540 C is not dense. High temperature titanium and oxygen, nitrogen, hydrogen reaction speed fast, easy to generate a brittle material, the welding is very poor, so in order to ensure the welding quality of the titanium tube, titanium clad tubesheets, we start from the aspects of material structure and equipment, through technological test and welding procedure qualification, some of the data.

The use of titanium steel composite pipe plate and titanium tube welding after expansion of the manufacturing process, in order to ensure the quality of products manufacturing, we made following the technological property test.

Tube sheet and tube bundle expansion of technological test the cooler requirements first expansion after welding, the strength from expansion to ensure welding play a major role in sealing. In order to ensure the expansion of the strength of the tube sheet and tube bundle expansion process test.

After the test, we used the method of measuring pressure to check the expansion quality, determine the expansion of the number of times and the expansion of the relay process parameters, to ensure that the tube expansion rate of 20 to 15 degrees per cent, to meet the design requirements.

Test of welding position of titanium tube bundle and tube sheet.

Through welding experiment found that when titanium tube to tube sheet used for all position welding, argon filling protection required drag cover tracking protection tube head heating zone, so the weld tube bundle need two operations, and should cooperate closely, once with good, easy to make the tube head oxidation discoloration, influence the quality of welding. And in the horizontal position welding, in argon protection cover welding pipe head, not only has good protection effect, can ensure the welding quality, and the operation is convenient, as long as a person can operate, a argon protection can welding 10 head tube, greatly accelerated the progress of welding. I plant in a pit, with horizontal position welding conditions, so the external cooler titanium tube bundle with horizontal position welding is the best welding position.

Titanium and oxygen have a strong affinity, at room temperature to form dense oxide film, the film is a serious obstacle to the implementation of welding, the severe oxidation of titanium tube welding, will cause very serious crack. The experiments show that the oxide film on the surface of the weld must be strictly cleaned up before welding and the source of harmful impurity is eliminated.

In the pipe carefully cleaned with acetone before the pipe hole oil, dirt and tubing.

And bundle welding before the deal was weld area of mechanical cleaning (with a diameter of 0.1mm austenitic stainless steel wire brush removal to be welded on the surface of the oxide layer), defatted (scrub with acetone), and check with the white silk does not change color, qualified rear can bundle welding, welding pause and non welding area with white silk covered, is strictly prohibited dust and dirt into welding area.

The clearing of titanium tube, titanium tube surface quality and decide, surface oxidation is not serious, titanium tube, the outer surface of the tube especially 100mm end tube, after washing with acetone clean wear tube, before welding again with acetone wipe wash pipe head and pipe inner hole.

Surface oxidation of titanium tube, the two ends of the tube before the 100mm must be carried out at the end of the pickling process, pickling formula for the:

0=5:20:75's HF:HNO3: (volume ratio)

The temperature is room temperature, the pickling time is 2 to 5 minutes, after the acid wash, rinse with clear water immediately, can not remain acid liquid. After pickling titanium tube was silver white.

Welding of titanium tube in the process of test and welding procedure qualification based on, we find out the basic characteristics and to determine the manufacturing process of tube bundle: titanium tube welding after expansion, and the use of horizontal position welding process.

For the control of welding deformation, strengthen the titanium welding cooling, improve the protection effect, titanium tube bundle welding, pipe plug copper block.

Using manual tungsten argon arc welding process, choose the reasonable welding specification and thoroughly clean the tubesheets and the tube end and debris in the oxide film, in reliable protection conditions (making suitable protection cover), titanium tube, titanium clad tubesheets welded joints can get satisfactory quality.